Acid Catalyzed Hydration of Alkenes

hello class the next addition reaction that we're going to look at is called an acid catalyzed hydration so what does the words mean we're hydrating so that means we're adding water across the double bond and in order to get that to occur we need to add a catalyst so a prime example of this process would be you have your alkene and you could represent this reaction in many ways but I'll start off with just one for right now okay I'm going to just say we're going to add the hydronium ion and when we do that hydronium is basically when you take water right and you add an acid to it and acids can be represented by just a proton and so that is going to generate our hydronium so in order to generate that hydronium what we typically do is we can write it like this you can say hey we're going to add some water and we're going to give a catalytic amount of sulfuric acid and typically you'll see a little cat with an abbreviation for catalysis or catalyst you could also see it represented by this put in Brackets that implies that it's the catalyst but I like to use this method right here okay so you could say okay this Catalyst sulfuric acids can represent the h plus here and so what happens when you take water and put in a few drops of sulfuric acid to it you're going to generate the hydronium you're going to get some acid solution okay so what happens when you take an alkene put it in some water and a catalytic catalytic amount of sulfuric acid is you're going to follow the marconikoff rule and we're going to add a hydrogen on one of these carbons where's the hydrogen wire what carbon carbon one or carbon two will you add the hydrogen to orconikoff rule says you have to add it to the carbon that has the most hydrogens there it is so we are going to add hydrogen there and then by default the oh is going to go there right now so this may not be making a complete sense quite yet but let's just bear with me now okay so I'm going to uh so this hydrogen right here is that hydrogen there and I'm not going to repres draw that in for right now so why is this called the hydration because what have we added across this double bond we've added this hydrogen and that o h what are those two together that's H2O so we've added water across that double bond so that is a addition reaction and these acid catalyzed hydrations follow the marconikov rule now why would they follow the marconikoff rule well it all comes down to the mechanism so the mechanism is very similar to what was the last reaction we did we did the hydration Hydro halogenation yeah it's the mechanism is very similar to the hydrohalogenation so the first step is we have to understand that this combination of water and sulfuric acid is going to generate the hydronium ion and I'm going to represent the hydronium ion like this and the reason why I wanted to draw it that way is because it just makes it easier for the mechanism so the first step is this alkina's electron rich this hydrogen right here is the electron pore so it's going to grab it break that and then we are going to go and add the whoa and add the hydrogen according to marconikos rule right so we'll add the hydrogen there that will generate a secondary carbocation Plus water so you see how the hydronium get converted into the water now we so the same principles for carbocations whenever you form a carbocation can it rearrange and in this case there's it wouldn't rearrange because we're at a secondary carbocation or a tertiary sorry a tertiary carbocation very very stable so the next step in the mechanism is now our water is a weak nucleophile and it's going to come in and attack the carbocation and so I'm going to draw that down here so I'm just when the water attacks there's two hydrogens attached to it right but now auction has what three bonds so that makes that oxygen atom a positively charged species and maybe we can draw this out as a bond and we call this species the oxonium ion okay let's do that in a different color here so when you have an oxygen attacked to a carbon chain here and it's possibly charged we call that the oxonium ion now this oxonium ion because it's possibly charged that's not going to be the end product your end product is more often than not going to be neutral because charged species are too high in energy and they're going to break apart or they're going to react to gain more stability by becoming neutral so what we do well what's the next step then to get that oxonium ion neutral is we're going to have water present right not all of the water is going to be converted into hydronium because there's large excess of water and a catalytic amount of sulfuric acid so when you have a catalyst you usually don't have a lot of it you don't need a lot of it because a catalyst is never consumed in a reaction it's regenerated so we have some water still a lot of water just hanging around so we're going to use that water as a base now to make this oxonium ion neutral so we're going to come here and grab a proton and do a proton transfer step here to generate our neutral product and more often than not you're not going to be shown that the hydrogen was also added there but look at what happens when the water grabs the hydrogen off the oxonium ion what do we generate we generate hydronium again so we have just regenerated the Catalyst and this just keeps going and going so that is a acid catalyzed hydration of an alkene and you can see that the mechanism the first part right here this mechanism is very very similar to uh the hydro halogenation reaction okay so another thing to note is the rate of these acid catalyzed hydrations so what I have here are three different types of alkenes and the difference between the alkenes is the substitution pattern and what we're going to do is we're going to tr time how long this reaction takes right here this top one and whatever it's time we're just going to say okay we're going to call that a relative rate of one and then we're going to compare these other two to this reaction rate and what we're going to find is that just by adding one alkyl group to this alkene increases the rate 10 to the six times that's a million times faster crazy and then if we add a second one look at what this it goes 10 to the 11 times faster can you look at the so there's the data can you use the chemical principles that I've taught you up to this point to like rationalize why is this a thing well it all comes down to carbocation stability right look at this when we have this guy what does marconikoff rule say is going to what's the first intermediate going to be the hydrogen is going to add there to generate what a secondary carbocation but when you compare this guy right here what do you have you have a secondary versus a tertiary so that tertiary carbocation is way more stable so the reaction is going to go a whole lot faster that's basically what it boils down to Isn't that cool so what's what's next here that we need to talk about we can talk about equilibrium now how we can control which direction we want it to go when we take a look at Acid catalyzed hydrations of an alkene what's interesting is that it is an equilibrium process so what we have here is in the forward direction we have the acid catalyze hydration but in the reverse reaction what are we doing we're doing an elimination why are we doing an elimination because look at what we're eliminating when we go from this alcohol to the alkene what are we losing o h and this hydrogen you can see the oh is no longer there and that one of those hydrogens is taken off so what is that in Reverse called that is a acid catalyzed acid catalyzed dehydration the removal of water so could we also call this an elimination yes we could it's just this elimination reaction has a special name and that's called dehydration and in order to do this dehydration we have to have an acid catalyst so both these processes there's some sulfuric acid present so if you want to favor the alcohol what you're going to do let's make sure I get this right you're going to have dilute dilute sulfuric acid h2so4 there you go so if you do this if you take an alkene and place it into water okay and you add just a very little bit of a very little amount of sulfuric acid and it's very dilute then it's going to favor the alcohol in contrast if you want to favor the alkene you are going to have concentrated sulfuric acid okay so as we've seen in the previous Reactions where they were temperature they we could control equilibrium by temperature we can also control equilibrium by the concentration of reagents and it it boils down to a shotlay's principle and and how we can influence the equilibrium and where we want the reaction to go okay so let's use the shot lace principle to uh describe this okay so let's say we have this reaction here right alkane plus water what we're going to do is add a very small amount of sulfuric acid okay and then we let it sit and with that very small amount of acid equilibrium is going to eventually be reached okay once equilibrium has been reached how can you now from this point on force it either way so if you have if you want to favor the alcohol you want dilute sulfuric acid so how would you do that when you've already added sulfuric acid to get the reaction going how can you dilute the sulfuric acid well you would add water if you add more water to the reaction that's already at equilibrium the shot lace principle says hey you added water so we need to go in the forward reaction to make this product to get back to equilibria so if you want to favor the alcohol you dilute the sulfuric acid by adding more water Isn't that cool but then the opposite is true okay what could you do here if you want to Once equilibrium has been reached with a little bit of sulfuric acid we want that to actually now do the dehydration what would you do you would add more sulfuric acid and what what are you doing when you're adding more sulfuric acid you're basically diluting the amount of water so you could kind of look at it like hey you having less water so uh the shot lace principle says hey you've got to drive the reaction to the left to compensate for the amount of water that's uh being diluted down you could also do this um with distillation and you'll learn about distillation more in your orgo Labs but distillation is physically removing the water so if you have a chemical setup where it's removing water is the reaction's going then it's you can drive it to the left but if you don't have this fancy distillation set up just know add more water to dilute the sulfuric acid to drive it to the right if you want to drive it to the uh the alkene then you add sulfuric acid and keep that concentrated right and that can all be explained by um with shortlist principle now acid um acid catalyzed hydration can also generate stereocenters let's erase this do you recall when we were looking at Hydro halogenation where if I had this reagent right here PR not VR this hydrochloric acid there remember that reaction and we have this regiochemistry that we have to account for and that's uh explained by Marconi costs rule but then we have two different stereocenters right we have our R and our s and when we do this reaction we get a mixture of these products right remember why that was it was because the intermediate right here is what SP2 hybridized so it was flat and so you remember how if I it was actually drawn this way remember how I looked at it like this right there and then you have the P orbitals right here and so the chloride could attack from this side or this side with equal probability remember that well that same concept applies for acid catalyzed hydration if you have water with the acid Catalyst sulfuric acid like that what are you going to generate you're going to generate an out a mixture of alcohols with different stereocenters it's the same principle because what are we generating we are generating a carbocation and so then what's the next principle that we have to watch out for rearrangement so even with acid catalyzed hydration you have to worry about the stereochemistry and rearrangement so if we change this problem up a bit by just adding this right there we would have a mixture of these but then what else would we introduce now we would have a mixture of these sorry but then what else would we introduce now we would have to have a hydride shift which would give us that and then the water would come in and attack from this side and then we would do a proton transfer to get rid of the oxonium ion to give us that product so if this was our reaction condition this molecule here we have a mixture of this these two and this one but which one would be the major product it would have this one would have to be the major product why because it came from a more stable tertiary carbocation versus the secondary the secondary carbocation gave us these products right there and then the tertiary gave us the major same principles just different products Isn't that cool so we've seen this reaction already where you take this alkene and treat it with some water with a catalytic amount of sulfuric acid right and we said that we are going to get a mixture of products and this one right here is going to be the major because it originates from a carbocation rearrangement from the secondary carbocation to a tertiary right well what if we don't want rearrangement to occur at all and just have this as our product what if we wanted this as our major product and this doesn't form at all there is a way to do that and there there's a named reaction and that's called The oxymer Creation so okay I'm cutting off a little bit so I need to lower it down oxymear creation like Mercury there oxymorcuration D mere creation is it all on the board okay so the reaction that we want to do is the oxymorcration demure creation and what we're going to add in order to get that to occur is it requires two steps or what's a better way two reactions so you're going to do one reaction and I'm going to represent that by the number one so the first reaction that you're going to do is you're going to treat it with uh what's the name of it here mercuric acetate mercuric acetate looks like this so we have our Mercury and then our acetate like so so there's our me um miracree species and you need some water okay and then the second step okay is you treat it with sodium borohydride like that if you treat this alkene with two or with these two reactions here we have your our Mercury acetate or we could call it Mercury Dia acetate and water and our sodium borohydride we will generate this only as our product okay now how stepwise what's going to happen here when we do this you can also see that this is the marconikov product right so that's that's a good thing so the key about this reaction right here is there's no carbocation rearrangement so the after you do the first step this is what you generate right here okay let me show you here after the first step you're going to generate this molecule right here you will generate oh h where's my there it is Mercury oh AC okay so after the first reaction this is what you generate and then the second step is the D mere creation with the Sodium borohydrate and that just chops off this metal piece to give us it chops off that metal the Mercury and replaces it with the hydrogen right there to give us our product so you can see this and this is the same thing okay now how does it go about doing that well the mechanism is going to show us how that occurs I just want to give you the pieces first of how how it's going to proceed without showing you the mechanism arrows and now we will go to the mechanism okay and the mechanism is going to show us why there's no carbocation rearrangement and why that's so important now in order to understand this reaction we need to understand this reagent right here and I misspoke what I called it Mercury diacetate it's just Mercury acetate to be more precise it's humir Curry II acetate meaning it's um Mercury to acetate like that okay so what does that look like well you're going to have mercury attached to two acetate molecules like so okay now what does acetate look like what's that that's going to look like so this I could also drawn it like this like that so right there there's our that's our acetate piece right there okay so this and this are the same thing but we are going to abbreviate it just to make life a little slightly easier okay so when you take the Mercury acetate and add it into some water all right what's going to happen is it's going to break apart it's going to break apart into that Mercury Plus plus our acetate pie on there like that okay so that's what's going to happen when you place the Mercury acetate into water it breaks apart into this and what's so good about that is this is a very strong electrophile very very strong and so the alkene now can react with the Mercury species okay let's see and we could call this guy a meturic cation all right we can name it that or so our mercuric cation is going to react with our alkene so let's take a look at how that's going to proceed okay what's going to happen is we have our alkene right here which is electron rich and now we have what do we have here we have our Mercury meteoric cation here like so and that's positively charged okay but it also has some a lone pair there which is going to be important to understand now what's cool about this mechanism here is that it's very similar to [Music] to let's say it reacting with an acid what's the mechanism we have this and it attacks so the kind of the same idea here this is going to come in and attack because it's very electrophilic but what's interesting at the same time that the pi electrons in this double bond come in and attack the Mercury atom the lone pair on the Mercury comes in and attacks there so what does that give us it gives us a species that looks like this so here's our Mercury I'll draw the oh acetate there and then we have something that looks like that right and so now our mirror crease still going to be positively charged right there so this species right here we see that it's a three-membered ring right there then we we're going to call that the mercuriic uh wow this this is so the word is just so hard for me to say it's just it's weird okay so let me write it down that's a c there we go foreign there it's a mirinium ion that's what that three-membered species looks like or it's called okay so we have our ion there now this three-membered ring prevents any carbocation rearrangement that's the cool thing all right because when you compare it to the other one to the other reaction remember how you treated it with the hydronium and it went like this and what did we generate we generated a secondary carbocation that that would then rearrange do you see here when we use the Mercury the carbo the positive charge is not on any of the carbons so that's key so it's not going to rearrange hey now the next step in the mechanism of this went to there the next step in the mechanism is water reacting with the murikinium ion so the question then is does it attack this carbon I'll call it carbon one or carbon 2. because we have a weak nucleophile so which one does it attack and the answer I already showed you the pro the product after the first reaction this water molecule comes in and attacks carbon one and then the carbon Mercury Bond breaks and that's going to give us this product that I'm going to draw over here so I have to be positively charged and then we have our Mercury acetate here like that okay and then we are going to do a proton transfer all right a proton transfer the proton transfer is not going to get this oxonium ion here to get rid of that positive charge how would we do that well there's a lot of water present okay a lot of water present so we could envision a water molecule acting as a base going to come and do this proton transfer to give us this all right oh Mercury but so that is the product after the first reaction now we need to rationalize and figure out why did the water attack carbon one and not carbon two that's what we need to figure out and so I'm going to pause the video erase the board so we can talk about that so the Mercury ion here the way I've drawn it shows that mercury has three bonds but in reality when mercury has these three bonds it's very very unstable and at more looks like this we could let's look at two options here okay we could have mercury that looks more like this where it's a solid Bond there and a dotted Bond there so it's unfortunately it's kind of a partial Bond and so when it's a partial Bond like that what we're going to have now is a partial positive on Mercury and a partial positive on the carbon or we could have a situation and throw I have to draw it a little bit smaller here where we have our Mercury essay where that's the solid line and then that's the okay so that would still have a partial positive and that would have a partial positive okay now comparing these two possibilities which one is the more likely structure well when I take a look at this carbon right here okay I see that this carbon is bonded to one carbon so that's kind of like a primary carbocation or we could say that's kind of like saying that's a partially a partial primary carbocation that's probably a better way of saying it but then when I take a look at this partial positive here I could say hey that partial positive is kind of like a second a partial secondary carbocation so when we compare these two scenarios just based off of our understanding of carbocations we know primary carbocations are very unstable don't form and secondary carbocations are more stable so if we say or bring those principles into this situation and just look at the partial charges we can clearly see that this partial charge right here is going to be more prevalent then that partial positive because this partial positive here is more stable and it's more stable because it has more alkyl groups attached so what we have here is only this one and because that has a a partial the the majority of the partial positive or the partial charge is going to be on this carbon so when you take your water molecule that is a weak nucleophile we could say very electron pore not so electron poor where's this electron Rich species going to be attracted to the most it's going to be attracted to the carbon that has the larger partial positive and so we could represent that kind of like this this carbo this carbon right here would have a much larger partial positive than that one because of the stability from the alkyl groups so what's going to happen is that the water is going to be attracted to that carbon so an oxymer creation reactions when the water does the attack okay so in this step right here when the water comes in to do the attack it's going to go for the more substituted carbon and then the carbon that's attached the more substituted carbon that's attached to the Mercury that bond has to break and so that would give us our product actor reaction One okay and that would give us that species right here and then you would do a proton transfer to take off one of those protons to give us our neutral product and there's gonna be some lone pairs there just like that okay now the next reaction I want to double check one thing here in the next reaction or reaction two is sodium borohydride now the mechanism for that is a radical mechanism so what we think it's kind of still not 100 sure but we just we know what the end result is and the end result is when you replace that or when you react to this species with sodium borohydride and sodium borohydride is what's called a reducing agent okay sodium borohydride is going to reduce our compound here and let's not run out of room you see how it's going to replace the Mercury with what the proton and so that right there this structure right there is our product so the moral of the story here and the cool thing about um the oxymear creation is the fact that there's no carbocation rearrangement so you get your one product so brief recap of what we've learned so far in regards to putting water across a double bond or a hydration reaction we have acid catalyzed hydration where we see that we get a mixture of products then we do the oxymearcreation demure creation reaction in which we get one product now we definitely can have um um the anatomers that will be that equal concentration now we have a third reaction that we can talk about that's really really cool and that's when we take the same compounds I'll show you the reagents in a minute but look at what happens here what we're going to generate is a anti-markconikoff product should see how when we're looking here from here to here to oh or the hydrogen skull where marconikov predicted they would go the hydrogen went there and then in this product right here where did the hydrogen go right there marconikoff product right but look at this reaction right here where did the hydrogen go it went right there so this is the anti-markconikoff product and how do you get a anti-marcoticoff product that is when you do a reaction that's called the hydroboration hydroforation oxidation that's that's the one word right there hydroboration I don't know why I made it look like that so we have hydro hydroboration oxidation reaction and this is another two-step reaction in which you are going to in step one you're going to treat the alkene with a borane bh3 that's called borane and then you're going to treat it and and it's going to be in a solvent called thf and thf stands for tetrahydrofuran it's just a common organic solvent okay so that's not too terribly important here well I let I retract that okay it needs to be in thf and then two the second step is so is the oxidation step and the way you're going to do this oxidation is with peroxide H2O2 and some base so the Heidelberg hydroboration is the first reaction and then the oxidation is the second reaction and when you you have to do both of these reactions in order to convert this alkene into this alcohol I want to take a moment to say hey it would be a great idea for you to create your notes in this fashion create it based off of functional groups so you will have a page in your notebook that says something something to the effect how to make alcohols because look I'll call alcohol alcohol three different ways so I would make a list in that section how to make alcohols well you can take an alkene and treat it with these different reagents and then as we progress through the the semester and into orgo2 you will learn even more reactions on how to make alcohols and you'll just keep adding to that list so this would be a really good idea to kind of categorize your reactions based off of what they make and the functional groups here are alcohol so how do you make alcohols here's three ways up to this point okay now let's uh delve into what's similar and what's different between these three reactions and the first thing that we've noticed that's different is hydroboration oxidation reactions are anti-markconikoff and so I think that's so cool because you have the same starting materials okay but you're going to get three different types of alcohols you if you you could get this one or these guys or this one you can see where the alcohols are uh are at different places so cool okay another factor that we need to be aware of is the stereochemistry so if we treat that with our borane right here thf thf and step two the oxidation right the stereochemistry is really important well can you pause the video and tell me where the alcohol is going to go is it going to go on carbon one [Music] or carbon two what do you think well it's going to go to the less substituted side so we're going to have the alcohols go here right [Music] so that's the regiochemistry right the oxygen atom is going to go to the less substituted side or we could say the hydrogen adds anti-markconikoff so this is the anti-markconica product but what is about the stereochemistry here and that's the cool thing about this reaction and some kind of unique to it is the way that it adds is you'll notice that the hydrogen that is being added and the alcohol that is being added are on the same side they're both wedges so yes this is a addition reaction yes it is also called the hydroboration oxidation reaction but then we could say hey what type of addition reaction is it and we call it a sin Edition a sin Edition is telling us that the the two groups that are being added and in this case it's a hydrogen and an alcohol are on the same side all right now you could have very well because what's interesting about this reaction is the fact that these carbons right here are SP2 hybridized so that means they're flat so if I take this molecule okay well it's going to be hard to draw on the board but if I take this molecule represented by my hand okay and I take it and I rotate it like this all right now my thumb I want my thumb to represent this methyl group right here okay when I take it and rotate it you see how the methyl group's pointing out pointing towards my chest okay if I represent the molecule like that all right these carbons right here represented right here we have ntp orbitals above and below my hand so when this reaction occurs the reaction can occur on the top of my hand which is represented by these wedges or the reaction can happen underneath my hand and so if the reaction happens underneath my hand then we would have something that looks like this you can see that they're both sin Edition because the hydrogen and the alcohol are the same on the same side they could either be both wedges or both dashes they're both sin Edition the only difference between these two is the approach of the reagents is that from the top or from the bottom what you will never see with hydroboration oxidation is a product that looks like this [Music] like that is this still an addition reaction yes it is because we've added a hydrogen and an alcohol across that double bond but this is called a anti addition and you do not have anti-additions with the hydroboration oxidation that is very very important to realize right I want to end this video on just understanding why hydroboration is um sin Edition and the regiochemical outcome why is the anti-markconikoff and it boils down to the fact that Boron the Boron atom and borane right here it's just a tricky bugger it just is weird it's a it's a Lewis acid Okay so borane we have Boron right there we're going to have uh our h H here and another H here and this is It's SP2 hybridized because it's flat it's trigonal planar so it has a p orbital and it you can also see with boring that it only has six electrons and we've been taught that hey all atoms want to have an octet right Boron is weird in the fact that it's content with six but it still is like I need eight I need eight and so it's going to react to get eight electrons around it but the moment it gets eight basically what it's asking for it's like I hate this and it splits it back out and so boring or Boron the Boron atom is just a finicky element and so because of its finicky is it helps us understand the reactivity of certain things so let's take this molecule right here okay like this the H3 what I want to do is I'm going to take that to cyclopentane ring right there and I'm just going to tip it 90 degrees okay so if my hand represents the ring my thumb represents the methyl group and I just tip it like this okay well that's what I'm trying to represent then is it's going to look something like this okay it's going to be that methyl group right there is going to be pointing out at me all right when I just tip it like so okay now we have we need to make sure that we understand that we have a double bond here okay so what happens is because oh let's see here make sure there's the double bond there we go now when we look at it this way the borane molecule can approach from the top or from underneath right now the way that it approaches is very very important because let's contrast two different approaches here right let's do it like that okay let's consider two different approaches here all right and this so boring could approach like this right and let's get a different color here we could it's going to approach something like this so we have bh2 and I'm going to extend one of the hydrogens like that versus the opposite bh2 with the hydrogen extended like that okay now what what's interesting is uh boring is a Lewis acid so it wants electrons and we see the alkene is electron Rich so the alkene is going to attack the borane so we could see it like this bh3 so this is going to come in and attack it just like that okay but then what happens when that attacks okay when it attacks like that what are we going to generate we are generally going to generate a carbocation so when that reacts like that sorry let's keep it like that all right we are going to generate hey what if the borane I need to draw this up a little further okay so let's say the boring goes there bh3 okay minus and then there's a plus right there okay if that's the case um we generated carbocation right and then we can start having rearrangements but hydroboration oxidation doesn't do any rearrangement so this isn't right and the reason why this isn't right is because like I said the moment the Boron atom accepts two more electrons to have an octet it's like I hate this and it's like no I don't want it and so the mechanism how it reacts is very very interesting in the fact that if I show it here now what color should I use here so when these Pi electrons come in and attack boron like so it's like oh this sucks and then so instantly it breaks this Boron hydrogen bond and donates it down and so what does that do for us is it generates this product right here all right and we are going to have what [Music] um get my colors here there's our methyl all right what's going to happen is the boron it's going to be like that too and then that will be our hydrogen do you see how the Boron and the hydrogen add to the same side and it's adding to the same side because the moment the pi electrons come and attack the Boron it just gets all upset and just drops the hydrogen down to get back to only six electrons around the Boron atom and so that just happens so fast it's concerted that it adds in a sin addition like that all right but now the next consideration that we need to talk about is why does it add this way instead of this way all right why does it not do this because remember these Hydrox Hydro boration oxidation reactions are regioselective remember the if we did this reaction right here what would our product ultimately be after we do steps one through two all right we would have the ox the alcohol would go on the less substituted side it would be the anti-markconikoff and the hydrogen would be added there so in order to explain that it's we can talk about it uh via Electronics Electronics can help us understand that and sterics and due to the length of this video we will stop here and we'll pick that up into CL in class as to why is the hydroboration oxidation reaction regioselective

hello class the next addition reaction that we&#39;re going to look at is called an acid catalyzed hydration so what does the words mean we&#39;re hydrating so that means we&#39;re adding water across the double bond and in order to get that to occur we need to add a catalyst so a prime example of this process would be you have your alkene and you could represent this reaction in many ways but I&#39;ll start off with just one for right now okay I&#39;m going to just say we&#39;re going to add the hydronium ion and when we do that hydronium is basically when you take water right and you add an acid to it and acids can be represented by just a proton and so that is going to generate our hydronium so in order to generate that hydronium what we typically do is we can write it like this you can say hey we&#39;re going to add some water and we&#39;re going to give a catalytic amount of sulfuric acid and typically you&#39;ll see a little cat with an abbreviation for catalysis or catalyst you could also see it represented by this put in Brackets that implies that it&#39;s the catalyst but I like to use this method right here okay so you could say okay this Catalyst sulfuric acids can represent the h plus here and so what happens when you take water and put in a few drops of sulfuric acid to it you&#39;re going to generate the hydronium you&#39;re going to get some acid solution okay so what happens when you take an alkene put it in some water and a catalytic catalytic amount of sulfuric acid is you&#39;re going to follow the marconikoff rule and we&#39;re going to add a hydrogen on one of these carbons where&#39;s the hydrogen wire what carbon carbon one or carbon two will you add the hydrogen to orconikoff rule says you have to add it to the carbon that has the most hydrogens there it is so we are going to add hydrogen there and then by default the oh is going to go there right now so this may not be making a complete sense quite yet but let&#39;s just bear with me now okay so I&#39;m going to uh so this hydrogen right here is that hydrogen there and I&#39;m not going to repres draw that in for right now so why is this called the hydration because what have we added across this double bond we&#39;ve added this hydrogen and that o h what are those two together that&#39;s H2O so we&#39;ve added water across that double bond so that is a addition reaction and these acid catalyzed hydrations follow the marconikov rule now why would they follow the marconikoff rule well it all comes down to the mechanism so the mechanism is very similar to what was the last reaction we did we did the hydration Hydro halogenation yeah it&#39;s the mechanism is very similar to the hydrohalogenation so the first step is we have to understand that this combination of water and sulfuric acid is going to generate the hydronium ion and I&#39;m going to represent the hydronium ion like this and the reason why I wanted to draw it that way is because it just makes it easier for the mechanism so the first step is this alkina&#39;s electron rich this hydrogen right here is the electron pore so it&#39;s going to grab it break that and then we are going to go and add the whoa and add the hydrogen according to marconikos rule right so we&#39;ll add the hydrogen there that will generate a secondary carbocation Plus water so you see how the hydronium get converted into the water now we so the same principles for carbocations whenever you form a carbocation can it rearrange and in this case there&#39;s it wouldn&#39;t rearrange because we&#39;re at a secondary carbocation or a tertiary sorry a tertiary carbocation very very stable so the next step in the mechanism is now our water is a weak nucleophile and it&#39;s going to come in and attack the carbocation and so I&#39;m going to draw that down here so I&#39;m just when the water attacks there&#39;s two hydrogens attached to it right but now auction has what three bonds so that makes that oxygen atom a positively charged species and maybe we can draw this out as a bond and we call this species the oxonium ion okay let&#39;s do that in a different color here so when you have an oxygen attacked to a carbon chain here and it&#39;s possibly charged we call that the oxonium ion now this oxonium ion because it&#39;s possibly charged that&#39;s not going to be the end product your end product is more often than not going to be neutral because charged species are too high in energy and they&#39;re going to break apart or they&#39;re going to react to gain more stability by becoming neutral so what we do well what&#39;s the next step then to get that oxonium ion neutral is we&#39;re going to have water present right not all of the water is going to be converted into hydronium because there&#39;s large excess of water and a catalytic amount of sulfuric acid so when you have a catalyst you usually don&#39;t have a lot of it you don&#39;t need a lot of it because a catalyst is never consumed in a reaction it&#39;s regenerated so we have some water still a lot of water just hanging around so we&#39;re going to use that water as a base now to make this oxonium ion neutral so we&#39;re going to come here and grab a proton and do a proton transfer step here to generate our neutral product and more often than not you&#39;re not going to be shown that the hydrogen was also added there but look at what happens when the water grabs the hydrogen off the oxonium ion what do we generate we generate hydronium again so we have just regenerated the Catalyst and this just keeps going and going so that is a acid catalyzed hydration of an alkene and you can see that the mechanism the first part right here this mechanism is very very similar to uh the hydro halogenation reaction okay so another thing to note is the rate of these acid catalyzed hydrations so what I have here are three different types of alkenes and the difference between the alkenes is the substitution pattern and what we&#39;re going to do is we&#39;re going to tr time how long this reaction takes right here this top one and whatever it&#39;s time we&#39;re just going to say okay we&#39;re going to call that a relative rate of one and then we&#39;re going to compare these other two to this reaction rate and what we&#39;re going to find is that just by adding one alkyl group to this alkene increases the rate 10 to the six times that&#39;s a million times faster crazy and then if we add a second one look at what this it goes 10 to the 11 times faster can you look at the so there&#39;s the data can you use the chemical principles that I&#39;ve taught you up to this point to like rationalize why is this a thing well it all comes down to carbocation stability right look at this when we have this guy what does marconikoff rule say is going to what&#39;s the first intermediate going to be the hydrogen is going to add there to generate what a secondary carbocation but when you compare this guy right here what do you have you have a secondary versus a tertiary so that tertiary carbocation is way more stable so the reaction is going to go a whole lot faster that&#39;s basically what it boils down to Isn&#39;t that cool so what&#39;s what&#39;s next here that we need to talk about we can talk about equilibrium now how we can control which direction we want it to go when we take a look at Acid catalyzed hydrations of an alkene what&#39;s interesting is that it is an equilibrium process so what we have here is in the forward direction we have the acid catalyze hydration but in the reverse reaction what are we doing we&#39;re doing an elimination why are we doing an elimination because look at what we&#39;re eliminating when we go from this alcohol to the alkene what are we losing o h and this hydrogen you can see the oh is no longer there and that one of those hydrogens is taken off so what is that in Reverse called that is a acid catalyzed acid catalyzed dehydration the removal of water so could we also call this an elimination yes we could it&#39;s just this elimination reaction has a special name and that&#39;s called dehydration and in order to do this dehydration we have to have an acid catalyst so both these processes there&#39;s some sulfuric acid present so if you want to favor the alcohol what you&#39;re going to do let&#39;s make sure I get this right you&#39;re going to have dilute dilute sulfuric acid h2so4 there you go so if you do this if you take an alkene and place it into water okay and you add just a very little bit of a very little amount of sulfuric acid and it&#39;s very dilute then it&#39;s going to favor the alcohol in contrast if you want to favor the alkene you are going to have concentrated sulfuric acid okay so as we&#39;ve seen in the previous Reactions where they were temperature they we could control equilibrium by temperature we can also control equilibrium by the concentration of reagents and it it boils down to a shotlay&#39;s principle and and how we can influence the equilibrium and where we want the reaction to go okay so let&#39;s use the shot lace principle to uh describe this okay so let&#39;s say we have this reaction here right alkane plus water what we&#39;re going to do is add a very small amount of sulfuric acid okay and then we let it sit and with that very small amount of acid equilibrium is going to eventually be reached okay once equilibrium has been reached how can you now from this point on force it either way so if you have if you want to favor the alcohol you want dilute sulfuric acid so how would you do that when you&#39;ve already added sulfuric acid to get the reaction going how can you dilute the sulfuric acid well you would add water if you add more water to the reaction that&#39;s already at equilibrium the shot lace principle says hey you added water so we need to go in the forward reaction to make this product to get back to equilibria so if you want to favor the alcohol you dilute the sulfuric acid by adding more water Isn&#39;t that cool but then the opposite is true okay what could you do here if you want to Once equilibrium has been reached with a little bit of sulfuric acid we want that to actually now do the dehydration what would you do you would add more sulfuric acid and what what are you doing when you&#39;re adding more sulfuric acid you&#39;re basically diluting the amount of water so you could kind of look at it like hey you having less water so uh the shot lace principle says hey you&#39;ve got to drive the reaction to the left to compensate for the amount of water that&#39;s uh being diluted down you could also do this um with distillation and you&#39;ll learn about distillation more in your orgo Labs but distillation is physically removing the water so if you have a chemical setup where it&#39;s removing water is the reaction&#39;s going then it&#39;s you can drive it to the left but if you don&#39;t have this fancy distillation set up just know add more water to dilute the sulfuric acid to drive it to the right if you want to drive it to the uh the alkene then you add sulfuric acid and keep that concentrated right and that can all be explained by um with shortlist principle now acid um acid catalyzed hydration can also generate stereocenters let&#39;s erase this do you recall when we were looking at Hydro halogenation where if I had this reagent right here PR not VR this hydrochloric acid there remember that reaction and we have this regiochemistry that we have to account for and that&#39;s uh explained by Marconi costs rule but then we have two different stereocenters right we have our R and our s and when we do this reaction we get a mixture of these products right remember why that was it was because the intermediate right here is what SP2 hybridized so it was flat and so you remember how if I it was actually drawn this way remember how I looked at it like this right there and then you have the P orbitals right here and so the chloride could attack from this side or this side with equal probability remember that well that same concept applies for acid catalyzed hydration if you have water with the acid Catalyst sulfuric acid like that what are you going to generate you&#39;re going to generate an out a mixture of alcohols with different stereocenters it&#39;s the same principle because what are we generating we are generating a carbocation and so then what&#39;s the next principle that we have to watch out for rearrangement so even with acid catalyzed hydration you have to worry about the stereochemistry and rearrangement so if we change this problem up a bit by just adding this right there we would have a mixture of these but then what else would we introduce now we would have a mixture of these sorry but then what else would we introduce now we would have to have a hydride shift which would give us that and then the water would come in and attack from this side and then we would do a proton transfer to get rid of the oxonium ion to give us that product so if this was our reaction condition this molecule here we have a mixture of this these two and this one but which one would be the major product it would have this one would have to be the major product why because it came from a more stable tertiary carbocation versus the secondary the secondary carbocation gave us these products right there and then the tertiary gave us the major same principles just different products Isn&#39;t that cool so we&#39;ve seen this reaction already where you take this alkene and treat it with some water with a catalytic amount of sulfuric acid right and we said that we are going to get a mixture of products and this one right here is going to be the major because it originates from a carbocation rearrangement from the secondary carbocation to a tertiary right well what if we don&#39;t want rearrangement to occur at all and just have this as our product what if we wanted this as our major product and this doesn&#39;t form at all there is a way to do that and there there&#39;s a named reaction and that&#39;s called The oxymer Creation so okay I&#39;m cutting off a little bit so I need to lower it down oxymear creation like Mercury there oxymorcuration D mere creation is it all on the board okay so the reaction that we want to do is the oxymorcration demure creation and what we&#39;re going to add in order to get that to occur is it requires two steps or what&#39;s a better way two reactions so you&#39;re going to do one reaction and I&#39;m going to represent that by the number one so the first reaction that you&#39;re going to do is you&#39;re going to treat it with uh what&#39;s the name of it here mercuric acetate mercuric acetate looks like this so we have our Mercury and then our acetate like so so there&#39;s our me um miracree species and you need some water okay and then the second step okay is you treat it with sodium borohydride like that if you treat this alkene with two or with these two reactions here we have your our Mercury acetate or we could call it Mercury Dia acetate and water and our sodium borohydride we will generate this only as our product okay now how stepwise what&#39;s going to happen here when we do this you can also see that this is the marconikov product right so that&#39;s that&#39;s a good thing so the key about this reaction right here is there&#39;s no carbocation rearrangement so the after you do the first step this is what you generate right here okay let me show you here after the first step you&#39;re going to generate this molecule right here you will generate oh h where&#39;s my there it is Mercury oh AC okay so after the first reaction this is what you generate and then the second step is the D mere creation with the Sodium borohydrate and that just chops off this metal piece to give us it chops off that metal the Mercury and replaces it with the hydrogen right there to give us our product so you can see this and this is the same thing okay now how does it go about doing that well the mechanism is going to show us how that occurs I just want to give you the pieces first of how how it&#39;s going to proceed without showing you the mechanism arrows and now we will go to the mechanism okay and the mechanism is going to show us why there&#39;s no carbocation rearrangement and why that&#39;s so important now in order to understand this reaction we need to understand this reagent right here and I misspoke what I called it Mercury diacetate it&#39;s just Mercury acetate to be more precise it&#39;s humir Curry II acetate meaning it&#39;s um Mercury to acetate like that okay so what does that look like well you&#39;re going to have mercury attached to two acetate molecules like so okay now what does acetate look like what&#39;s that that&#39;s going to look like so this I could also drawn it like this like that so right there there&#39;s our that&#39;s our acetate piece right there okay so this and this are the same thing but we are going to abbreviate it just to make life a little slightly easier okay so when you take the Mercury acetate and add it into some water all right what&#39;s going to happen is it&#39;s going to break apart it&#39;s going to break apart into that Mercury Plus plus our acetate pie on there like that okay so that&#39;s what&#39;s going to happen when you place the Mercury acetate into water it breaks apart into this and what&#39;s so good about that is this is a very strong electrophile very very strong and so the alkene now can react with the Mercury species okay let&#39;s see and we could call this guy a meturic cation all right we can name it that or so our mercuric cation is going to react with our alkene so let&#39;s take a look at how that&#39;s going to proceed okay what&#39;s going to happen is we have our alkene right here which is electron rich and now we have what do we have here we have our Mercury meteoric cation here like so and that&#39;s positively charged okay but it also has some a lone pair there which is going to be important to understand now what&#39;s cool about this mechanism here is that it&#39;s very similar to [Music] to let&#39;s say it reacting with an acid what&#39;s the mechanism we have this and it attacks so the kind of the same idea here this is going to come in and attack because it&#39;s very electrophilic but what&#39;s interesting at the same time that the pi electrons in this double bond come in and attack the Mercury atom the lone pair on the Mercury comes in and attacks there so what does that give us it gives us a species that looks like this so here&#39;s our Mercury I&#39;ll draw the oh acetate there and then we have something that looks like that right and so now our mirror crease still going to be positively charged right there so this species right here we see that it&#39;s a three-membered ring right there then we we&#39;re going to call that the mercuriic uh wow this this is so the word is just so hard for me to say it&#39;s just it&#39;s weird okay so let me write it down that&#39;s a c there we go foreign there it&#39;s a mirinium ion that&#39;s what that three-membered species looks like or it&#39;s called okay so we have our ion there now this three-membered ring prevents any carbocation rearrangement that&#39;s the cool thing all right because when you compare it to the other one to the other reaction remember how you treated it with the hydronium and it went like this and what did we generate we generated a secondary carbocation that that would then rearrange do you see here when we use the Mercury the carbo the positive charge is not on any of the carbons so that&#39;s key so it&#39;s not going to rearrange hey now the next step in the mechanism of this went to there the next step in the mechanism is water reacting with the murikinium ion so the question then is does it attack this carbon I&#39;ll call it carbon one or carbon 2. because we have a weak nucleophile so which one does it attack and the answer I already showed you the pro the product after the first reaction this water molecule comes in and attacks carbon one and then the carbon Mercury Bond breaks and that&#39;s going to give us this product that I&#39;m going to draw over here so I have to be positively charged and then we have our Mercury acetate here like that okay and then we are going to do a proton transfer all right a proton transfer the proton transfer is not going to get this oxonium ion here to get rid of that positive charge how would we do that well there&#39;s a lot of water present okay a lot of water present so we could envision a water molecule acting as a base going to come and do this proton transfer to give us this all right oh Mercury but so that is the product after the first reaction now we need to rationalize and figure out why did the water attack carbon one and not carbon two that&#39;s what we need to figure out and so I&#39;m going to pause the video erase the board so we can talk about that so the Mercury ion here the way I&#39;ve drawn it shows that mercury has three bonds but in reality when mercury has these three bonds it&#39;s very very unstable and at more looks like this we could let&#39;s look at two options here okay we could have mercury that looks more like this where it&#39;s a solid Bond there and a dotted Bond there so it&#39;s unfortunately it&#39;s kind of a partial Bond and so when it&#39;s a partial Bond like that what we&#39;re going to have now is a partial positive on Mercury and a partial positive on the carbon or we could have a situation and throw I have to draw it a little bit smaller here where we have our Mercury essay where that&#39;s the solid line and then that&#39;s the okay so that would still have a partial positive and that would have a partial positive okay now comparing these two possibilities which one is the more likely structure well when I take a look at this carbon right here okay I see that this carbon is bonded to one carbon so that&#39;s kind of like a primary carbocation or we could say that&#39;s kind of like saying that&#39;s a partially a partial primary carbocation that&#39;s probably a better way of saying it but then when I take a look at this partial positive here I could say hey that partial positive is kind of like a second a partial secondary carbocation so when we compare these two scenarios just based off of our understanding of carbocations we know primary carbocations are very unstable don&#39;t form and secondary carbocations are more stable so if we say or bring those principles into this situation and just look at the partial charges we can clearly see that this partial charge right here is going to be more prevalent then that partial positive because this partial positive here is more stable and it&#39;s more stable because it has more alkyl groups attached so what we have here is only this one and because that has a a partial the the majority of the partial positive or the partial charge is going to be on this carbon so when you take your water molecule that is a weak nucleophile we could say very electron pore not so electron poor where&#39;s this electron Rich species going to be attracted to the most it&#39;s going to be attracted to the carbon that has the larger partial positive and so we could represent that kind of like this this carbo this carbon right here would have a much larger partial positive than that one because of the stability from the alkyl groups so what&#39;s going to happen is that the water is going to be attracted to that carbon so an oxymer creation reactions when the water does the attack okay so in this step right here when the water comes in to do the attack it&#39;s going to go for the more substituted carbon and then the carbon that&#39;s attached the more substituted carbon that&#39;s attached to the Mercury that bond has to break and so that would give us our product actor reaction One okay and that would give us that species right here and then you would do a proton transfer to take off one of those protons to give us our neutral product and there&#39;s gonna be some lone pairs there just like that okay now the next reaction I want to double check one thing here in the next reaction or reaction two is sodium borohydride now the mechanism for that is a radical mechanism so what we think it&#39;s kind of still not 100 sure but we just we know what the end result is and the end result is when you replace that or when you react to this species with sodium borohydride and sodium borohydride is what&#39;s called a reducing agent okay sodium borohydride is going to reduce our compound here and let&#39;s not run out of room you see how it&#39;s going to replace the Mercury with what the proton and so that right there this structure right there is our product so the moral of the story here and the cool thing about um the oxymear creation is the fact that there&#39;s no carbocation rearrangement so you get your one product so brief recap of what we&#39;ve learned so far in regards to putting water across a double bond or a hydration reaction we have acid catalyzed hydration where we see that we get a mixture of products then we do the oxymearcreation demure creation reaction in which we get one product now we definitely can have um um the anatomers that will be that equal concentration now we have a third reaction that we can talk about that&#39;s really really cool and that&#39;s when we take the same compounds I&#39;ll show you the reagents in a minute but look at what happens here what we&#39;re going to generate is a anti-markconikoff product should see how when we&#39;re looking here from here to here to oh or the hydrogen skull where marconikov predicted they would go the hydrogen went there and then in this product right here where did the hydrogen go right there marconikoff product right but look at this reaction right here where did the hydrogen go it went right there so this is the anti-markconikoff product and how do you get a anti-marcoticoff product that is when you do a reaction that&#39;s called the hydroboration hydroforation oxidation that&#39;s that&#39;s the one word right there hydroboration I don&#39;t know why I made it look like that so we have hydro hydroboration oxidation reaction and this is another two-step reaction in which you are going to in step one you&#39;re going to treat the alkene with a borane bh3 that&#39;s called borane and then you&#39;re going to treat it and and it&#39;s going to be in a solvent called thf and thf stands for tetrahydrofuran it&#39;s just a common organic solvent okay so that&#39;s not too terribly important here well I let I retract that okay it needs to be in thf and then two the second step is so is the oxidation step and the way you&#39;re going to do this oxidation is with peroxide H2O2 and some base so the Heidelberg hydroboration is the first reaction and then the oxidation is the second reaction and when you you have to do both of these reactions in order to convert this alkene into this alcohol I want to take a moment to say hey it would be a great idea for you to create your notes in this fashion create it based off of functional groups so you will have a page in your notebook that says something something to the effect how to make alcohols because look I&#39;ll call alcohol alcohol three different ways so I would make a list in that section how to make alcohols well you can take an alkene and treat it with these different reagents and then as we progress through the the semester and into orgo2 you will learn even more reactions on how to make alcohols and you&#39;ll just keep adding to that list so this would be a really good idea to kind of categorize your reactions based off of what they make and the functional groups here are alcohol so how do you make alcohols here&#39;s three ways up to this point okay now let&#39;s uh delve into what&#39;s similar and what&#39;s different between these three reactions and the first thing that we&#39;ve noticed that&#39;s different is hydroboration oxidation reactions are anti-markconikoff and so I think that&#39;s so cool because you have the same starting materials okay but you&#39;re going to get three different types of alcohols you if you you could get this one or these guys or this one you can see where the alcohols are uh are at different places so cool okay another factor that we need to be aware of is the stereochemistry so if we treat that with our borane right here thf thf and step two the oxidation right the stereochemistry is really important well can you pause the video and tell me where the alcohol is going to go is it going to go on carbon one [Music] or carbon two what do you think well it&#39;s going to go to the less substituted side so we&#39;re going to have the alcohols go here right [Music] so that&#39;s the regiochemistry right the oxygen atom is going to go to the less substituted side or we could say the hydrogen adds anti-markconikoff so this is the anti-markconica product but what is about the stereochemistry here and that&#39;s the cool thing about this reaction and some kind of unique to it is the way that it adds is you&#39;ll notice that the hydrogen that is being added and the alcohol that is being added are on the same side they&#39;re both wedges so yes this is a addition reaction yes it is also called the hydroboration oxidation reaction but then we could say hey what type of addition reaction is it and we call it a sin Edition a sin Edition is telling us that the the two groups that are being added and in this case it&#39;s a hydrogen and an alcohol are on the same side all right now you could have very well because what&#39;s interesting about this reaction is the fact that these carbons right here are SP2 hybridized so that means they&#39;re flat so if I take this molecule okay well it&#39;s going to be hard to draw on the board but if I take this molecule represented by my hand okay and I take it and I rotate it like this all right now my thumb I want my thumb to represent this methyl group right here okay when I take it and rotate it you see how the methyl group&#39;s pointing out pointing towards my chest okay if I represent the molecule like that all right these carbons right here represented right here we have ntp orbitals above and below my hand so when this reaction occurs the reaction can occur on the top of my hand which is represented by these wedges or the reaction can happen underneath my hand and so if the reaction happens underneath my hand then we would have something that looks like this you can see that they&#39;re both sin Edition because the hydrogen and the alcohol are the same on the same side they could either be both wedges or both dashes they&#39;re both sin Edition the only difference between these two is the approach of the reagents is that from the top or from the bottom what you will never see with hydroboration oxidation is a product that looks like this [Music] like that is this still an addition reaction yes it is because we&#39;ve added a hydrogen and an alcohol across that double bond but this is called a anti addition and you do not have anti-additions with the hydroboration oxidation that is very very important to realize right I want to end this video on just understanding why hydroboration is um sin Edition and the regiochemical outcome why is the anti-markconikoff and it boils down to the fact that Boron the Boron atom and borane right here it&#39;s just a tricky bugger it just is weird it&#39;s a it&#39;s a Lewis acid Okay so borane we have Boron right there we&#39;re going to have uh our h H here and another H here and this is It&#39;s SP2 hybridized because it&#39;s flat it&#39;s trigonal planar so it has a p orbital and it you can also see with boring that it only has six electrons and we&#39;ve been taught that hey all atoms want to have an octet right Boron is weird in the fact that it&#39;s content with six but it still is like I need eight I need eight and so it&#39;s going to react to get eight electrons around it but the moment it gets eight basically what it&#39;s asking for it&#39;s like I hate this and it splits it back out and so boring or Boron the Boron atom is just a finicky element and so because of its finicky is it helps us understand the reactivity of certain things so let&#39;s take this molecule right here okay like this the H3 what I want to do is I&#39;m going to take that to cyclopentane ring right there and I&#39;m just going to tip it 90 degrees okay so if my hand represents the ring my thumb represents the methyl group and I just tip it like this okay well that&#39;s what I&#39;m trying to represent then is it&#39;s going to look something like this okay it&#39;s going to be that methyl group right there is going to be pointing out at me all right when I just tip it like so okay now we have we need to make sure that we understand that we have a double bond here okay so what happens is because oh let&#39;s see here make sure there&#39;s the double bond there we go now when we look at it this way the borane molecule can approach from the top or from underneath right now the way that it approaches is very very important because let&#39;s contrast two different approaches here right let&#39;s do it like that okay let&#39;s consider two different approaches here all right and this so boring could approach like this right and let&#39;s get a different color here we could it&#39;s going to approach something like this so we have bh2 and I&#39;m going to extend one of the hydrogens like that versus the opposite bh2 with the hydrogen extended like that okay now what what&#39;s interesting is uh boring is a Lewis acid so it wants electrons and we see the alkene is electron Rich so the alkene is going to attack the borane so we could see it like this bh3 so this is going to come in and attack it just like that okay but then what happens when that attacks okay when it attacks like that what are we going to generate we are generally going to generate a carbocation so when that reacts like that sorry let&#39;s keep it like that all right we are going to generate hey what if the borane I need to draw this up a little further okay so let&#39;s say the boring goes there bh3 okay minus and then there&#39;s a plus right there okay if that&#39;s the case um we generated carbocation right and then we can start having rearrangements but hydroboration oxidation doesn&#39;t do any rearrangement so this isn&#39;t right and the reason why this isn&#39;t right is because like I said the moment the Boron atom accepts two more electrons to have an octet it&#39;s like I hate this and it&#39;s like no I don&#39;t want it and so the mechanism how it reacts is very very interesting in the fact that if I show it here now what color should I use here so when these Pi electrons come in and attack boron like so it&#39;s like oh this sucks and then so instantly it breaks this Boron hydrogen bond and donates it down and so what does that do for us is it generates this product right here all right and we are going to have what [Music] um get my colors here there&#39;s our methyl all right what&#39;s going to happen is the boron it&#39;s going to be like that too and then that will be our hydrogen do you see how the Boron and the hydrogen add to the same side and it&#39;s adding to the same side because the moment the pi electrons come and attack the Boron it just gets all upset and just drops the hydrogen down to get back to only six electrons around the Boron atom and so that just happens so fast it&#39;s concerted that it adds in a sin addition like that all right but now the next consideration that we need to talk about is why does it add this way instead of this way all right why does it not do this because remember these Hydrox Hydro boration oxidation reactions are regioselective remember the if we did this reaction right here what would our product ultimately be after we do steps one through two all right we would have the ox the alcohol would go on the less substituted side it would be the anti-markconikoff and the hydrogen would be added there so in order to explain that it&#39;s we can talk about it uh via Electronics Electronics can help us understand that and sterics and due to the length of this video we will stop here and we&#39;ll pick that up into CL in class as to why is the hydroboration oxidation reaction regioselective

Transcript for:Acid Catalyzed Hydration of Alkenes

Transcript for:
Acid Catalyzed Hydration of Alkenes