hello organic chemistry students in this video we're going to cover Class 2 carbon yels now please keep in mind a class one carbonel is the carbon of a carbonel possessing a good leaving group on it a chlorine and oxygen and nitrogen and things like that class two carbon yals how do they differ there is no good leaving group on the carbon of a carbon yield for class twos when we look at an aldah we have a hydrogen and a carbon chain now if a nucleophile was to attack this carbon and break open the double bond if we wanted to kick out the carbon chain the electrons would have to donate down and kick out the carbon with the electrons and that creates a carban very unstable on the other side if we donate the electrons down and kick out the hydrogen it's not a hydrogen it's actually kicked out as a hydride also Al a very unstable leaving group and that's why ketones and aldhy are Class 2 carbonal now there is chemistry that can be done on this class 2 functional group so let's imagine that we have just a nucleophile we're going to talk about what type of nucleophiles here in a moment the nucleophile can attack the carbon of the carbonal this does happen absolutely and what we are going to see here is that we form this tetrahedral intermediate the nucleophile has added and we've broken open the carbon oxygen double bond now if this negative charge donates down we're going to kick out a hydride the nucleophile or the carbon chain and that's what we're trying to say right here so in this case here we would have to kick out either let me go ahead and put an R right here a hydride or an R minus both of which are not going to happen so we are not going to see The Return of the carbonal in class 2 carbonal we will never have the hydrogen or carbon group leave the molecule not going to happen so now what this leaves us at is could we ultimately then form this tetrahedral intermediate work up the reaction and form this alcohol containing compound and this is something that we can form this is a possibility now we can form this Tet tedral intermediate but now the tetrahedral intermediate can also collapse and go back to starting material now the same is also true somewhat over here generally once we form this right here with a strong nucleophile we remain as this alcohol containing compound and it doesn't necessarily reverse but this can be reversible and that's very important to notice and we're going to see that here shortly in the cases of water adding into of the carbon of the carbonal so as a whole a nucleophile can attack the carbon of the carbonal and we form the tetrahedral intermediate that upon work up we'll get a hydrogen on that oxygen that was negative so if we have a weak nucleophile or good leaving group on this carbon we're going to see class one carbonal chemistry in order to help promote this chemistry we're going to need some strong types of nucleophiles now let me stress this can happen with a weak nucleophile as well a weak nucleophile can attack this carbon of the carbonal form the tetrahedral intermediate but it's going to reverse back to the starting material so we're going to favor starting materials over the tetrahedral intermediate but the stronger and stronger that nucleophile becomes strong nucleophile it becomes a bad leaving group which means we're going to favor the formation of the tetrahedral intermediate so let me recap that one more time the weaker the this nucleophile is the better a leaving group it is so the negative charge will donate down and we reverse the reaction back to starting material I'm not contradicting the fact that class 2 carbonal do not give us back the carbonel I'm just saying we get back the starting material it's not a new compound but if the nucleophile is a strong nucleophile we'll form more of the tetrahedral intermediate and upon workup we form our alcohol as shown right here now what can the nucleophile be and that's that's what we're going to be focusing on in this video what types of nucleophiles can do relevant chemistry in class 2 carbonal the first one that I'd like to talk about if I can move this up is the addition of water so let's go ahead and use water and our class 2 carbonal Chemistry abbreviating carbonal by a c so now this can be done on alahh and ketones and I'm going to go ahead and take H2O water has two lone pairs of elect R the lone pair can attack the carbon of the carbonal break open the carbon oxygen double bond in a reversible process we also can do a proton transfer and what we've just done actually I'm going to take a step back and I'm not even going to show I want to show the proton transfer step so what we've just formed is this oxygen with a negative charge here is the water that we just added in positively charged and there is a hydrogen on this carbon if we end up doing the proton transfer event right here still in equilibriums we form this functional group right here and this should look familiar from our oxidation of alcohols video this is a hydrate so a hydrate exists in dynamic equilibrium with its alahh or Ketone starting material if this was a ketone right or if this was an alahh right here we notice there's a hydrogen on that carbon if it was a ketone there'd be another carbon chain and and another carbon chain off this carbon of the former carbon yum now this is an entirely dynamic equilibrium process we're going back and forth back and forth so now could you imagine what if and I'm going to go ahead and do this in blue what if I added in an alcohol could this alcohol also attack the carbon of the carbon yel and break open the double bond it could in a reversible process so we have the oxygen with the negative charge we've just added in this oxygen and two carbon chain here's our hydrogen which is a positive charge doesn't this intermediate look identical to this one right here it sure does minus the fact that we have a carbon chain and a hydrogen versus two hydrogens as long as we have a hydrogen on the hetero atom and we can do this with sulfur and we can do this with nitrogen even phosphorus as long as there's a hydrogen there we can form our intermediate and then the negative charge will pluck that hydrogen off neutralizing the positive charge and we form this new functional group right here now we're going to get into more details of that here in one moment but I want to stress that we can have any of these atoms right here in place of the oxygen do this chemistry but I want to focus it on the oxygen because this is going to become very important when we start talking about carbohydrates and especially with its applications to biological chemistry how we live as humans so when an alahh reacts with an alcohol right here we form this new functional group right here and I want to pay special attention I want to pay special attention to this carbon right here and keeping in mind that carbon right there I want to ask what functional groups are on this carbon so here oops let me try to move this back here on this carbon this carbon is part of an oxygen carbon Bond right here so that is definitely an ether functional group but now this carbon is also part of this oh and that is an alcohol now we could call that this carbon in question with the star next to it is both an ether and an alcohol two separate functional groups but it's not there's a new name for this functional group right here I know that sounds crazy so when you have a carbon that's both an ether and an alcohol what we are going to call this is a Hemi acetal what does this come from Hemi is referring to this alcohol group right here as well as this ether linkage right here the tal is also referring to the ether linkage and the ace part right here is referring to the fact that this all came from an aldhy so if it's coming from an aldhy the aldhy reacts with the alcohol to form this Hemi acety so if this was a ketone right here do we form a Hemi acety out of that and the answer is no because a Hemi acety refers to an alahh reacting with an alcohol to form this new acety linkage system right here so if I move this up for a second let's go ahead and take a Ketone functional group now and react it with the same alcohol the lone pair of electrons will come in Attack the carbon of the carbon y let me show that other electron of the lone pair break open the carbon oxygen double bond in a reversible process we form an oxygen with the negative charge we have this oxygen that is now protonated we steal that hydrogen oops that is the wrong Arrow we steal this hydrogen giving electrons back to oxygen and in a reversible process what have we just formed we have formed a carbon right here that is part of an ether functional group as well as an alcohol functional group what's the difference this carbon doesn't have a hydrogen on it this carbon right here one two three bonds so there's a hydrogen right there and that's what makes this lower one right here a h hemiketal so an acetal is coming from an aldhy starting material a ketle is coming from a ketone and this is all dynamic equilibrium within the solution so an aldhy can exist in equilibrium with an alcohol with an alcohol being present I should say with its Hemi acety form and a ketone and an alcohol can exist in its hemiketal form dynamic equilibrium back and forth back and fourth so what I'd like to do now excuse me is talk about how we can push this reaction towards another type of functional group and let me go ahead and open up the next page to talk about that excuse me what I'd like to do right here is start off with this functional group as shown and before I do anything what functional group am I showing you right here this carbon oops this carbon is part of an ether part of an alcohol so it's either a Hemi acety or hemiketal and this carbon has one hydrogen hanging off of it so this is a Hemi acety wonderful if I take this Hemi acety and treat it with H+ and another alcohol what are we going to form we are going to form this functional group right here where this oxygen right here is this oxygen right there we are also going to form a little bit of water as a byproduct so this oxygen with a square next to it is this oxygen right here let's go ahead and push the arrows for this reaction the oxygen right here is going to pick up this proton in a dynamic equilibrium process and we are going to protonate that water or that alcohol and create what looks like to be water water is a fantastic leaving group but sadly that oxygen that water can't just leave cuz that would create a primary carbocation which is no good but luckily there's an oxygen right here with lone pairs that could donate electrons down to this carbon right here to allow this oxygen carbon bond to break and what we have just formed in dynamic equilibrium again is a carbon oxygen double bond that's positively charged so doesn't this kind of look like a carbon yal it kind of does think about those alahh and ketones right a carbon oxygen double bond enter in our second alcohol that second alcohol with its lone pairs could attack the carbon of that carbonal like functional group give electrons back to oxygen and when this happens we now have this oxygen that's protonated so it's still a good leaving group but then we can lose this proton and that last step occurs in an irreversible step so in that irreversible step we form this new functional group that's locked it doesn't change it's not going away so now isn't this carbon right here part of two different ether linkages it is it's not part of an ether and alcohol anymore it's part of two ether linkages now if you also look at this carbon there's still a hydrogen on it which means it came from an alahh so we're still looking at an ace but now it's not a Hemi acetal because we don't have an alcohol this is just called a acety so an acety is defined as having a carbon that is connected or is a part of two ether linkages right here and this is very important for carbohydrate chemistry now can the same thing happen for ketones absolutely a ketone can undergo the same exact chemistry that I'm showing you right here so let's go ahead and show this Hemi acetal oops show this Hemi acety right here and if I react it with H+ so notice the H+ is essential and this alcohol right here doesn't matter what the alcohol is any alcohol will do this what we are going to form is is that this lower keep losing a carbon here or adding a carbon this lower ether remain Remains the Same and then we add the alcohol carbon this one right here or the alcohol oxygen and that's what's added right there as well as forming a little bit of water so in both cases small amounts of water are formed in this reaction and that's important to know small amounts of water we still have H+ but we don't have a lot of water in this reaction why am I stressing that it's going to become very important here in a couple of minutes so let's go ahead and talk about a biological example of this oops what I'm going to draw right now is going to look like a horrible big ugly looking molecule so here's an aldhy right here I'm showing all the carbons I'm going to show this o here a hydrogen a carbon and an o and a hydrogen carbon o and a hydrogen carbon o and a hydrogen and a carbon with two hydrogens and an O we're going to go into far more detail on this molecule soon enough but what I want to do right now is call this carbon 1 2 3 4 5 and six we have an alide we have multiple alcohols don't we could one of these alcohols attack the carbon of this carbon yel and form a Hemi acetal yes it can and what happens here in a d dynamic equilibrium processes we are going to form this group right here let me make that look a little bit nicer so here carbon 6 is pointing up carbon 5 is pointing down carbon 3 is going up down and we're going to use a squiggly line we're going to talk much more about this later on so here is carbon 5 4 3 2 and 1 so I'm having the oxygen on carbon 5 attack this carbon of the carbon yum why is it that alcohol we're going to talk about this later in the carbohydrate section what we've just done is we just took a molecule that we call glucose and formed it into its Alpha Beta glucose form now if this is D or L glucose we're going to cover that later on right now all we care about is that we're in this cyclic structure and this is a dynamic equilibrium but this dynamic equilibrium is kind of a lie let if I can get the Eraser going there it is let me show the stressed arrows for this dynamic equilibrium 98% of glucose will exist in this cyclic form why is this a good thing for us we live in an oxidizing environment that's our world ooh secondary alcohol primary alcohol couldn't we oxidize any of those alcohols to an alide and ketones we could so that means the straight chain glucose is subjectable to the oxidizing conditions of our world which would take glucose and transform it into a noncarbohydrate compound which our body could not use for energy we need glucose for energy so when it's in the straight chain right here it's very much in danger of being oxidized but when it's in the cyclic structure right here it's more stabil it's more structurally stable and this confer right here protects it from oxidation so when we're in the cyclic form of the carbohydrates they're protected from our oxidative environments now keep in mind this is a dynamic equilibrium so this is the form of glucose that keeps it protected but this is the form of glucose that we need to activate glycolysis and push it through doing G glycolysis from glucose to glucose 6 phosphate to fructose 6 phosphate to fructose 16 diphosphate then dihydroxyacetone glycer alide 3 phosphate and continuing through to form two pyrates and a total net of two ATP and we're going to be talking about that here shortly in this class so when we form a whole bunch of this cyclic form there's a little bit in the straight chain that our body can use really quickly and once we consume it a little bit more of this ring opens again that we consume oh a little bit more ring opens again and we consume it so we know about this ring opening and closing as a dynamic equilibrium so the acet the Hemi acety exists in dynamic equilibrium with its aldhy and it's alcohol starting materials wonderful now we're going to talk about disaccharides when we talk about carbohydrates and those are going to be in the acetal functional groups not going to draw them right now we're going to talk about them in carbohydrates but I want to talk about how we can take an acetal or a ketal and break it into its Hemi acety or hemiketal form so what I like to draw right here is this acetel when I take this acetel and I react it with H+ and water when I put water over that reaction Arrow am I saying just one equivalent of water or huge excess of water and you're right we are saying that this is present in excess so remember when we're forming the Hemi atiles and then the acetes I said we form a little bit of water That's essential here in order to take this acetel and break it open to either this Hemi acetal or I shouldn't say or if both of them do form let me get the Eraser marker there come on eraser there it is plus this Hemi acety we get both of them and both of them are in dynamic equilibrium with this alahh right here now in the first step right here actually I'm getting ahead of myself I'm going to stop right there over here either one of these oxygens could pick up this proton right here here so either one could attack this proton I'm going to show this top one attacking it and this is done in a dynamic equilibrium process so here's this oxygen picking up that proton positively charged oxygen lone pairs on that oxygen the lone pair could donate down and push out this decent leaving group because when oxygen is positive it's a decent leaving group and we've just formed this carbonal species again which looks very familiar when we took a Hemi acle to the acety now we do still have the alcohol that we just kicked out and could that alcohol add back through it sure could but let's not forget that we have a huge excess of water here that adds in to form and do a proton transfer our Hemi acetel which is in dynamic equilibrium to its aldhy starting material now in blue could this oxygen pick up this proton first it sure could so there's the oxygen protonated right here this oxygen now with its lone pairs could donate electrons down push out this alcohol and what do we form oh look at that an activated carbonal species to which water will come in attack donate electrons up proton transfer and what do we now have but another Hemi acetel which is in dynamic equilibrium with its aldah counterpart so this is called the hydrolysis of an acetel and a Ketel they both work identical so if I started off with a ketal these arrows are identical to the ones with an acetel there is nothing different what soever and I cannot stress that enough so in this video right here we talked about how an alahh and Ketone when a reaction occurs we don't get the carbon yield back it's gone it's not coming back if a reaction actually occurs we talk about how a really good nucleophile will attack the carbon of the carbonal and will form the tetrahedral intermediate that'll become proteinated upon workup and we form an alcohol we shown how water can add into an aldhy or Ketone which is a total refresher from our oxidation of alcohol video and then we saw the formation of hem acetes andales Alid I'm sorry um acetes and ketals the last thing I'd like to do really quickly is I just want to draw a random molecule there's that and I want to ask some questions what functional groups do we have present in this molecule right here so now when we look at this it looks like we are having an ether functional group here and an ether functional group here uh oh this carbon's part of both of those ethers aren't they so if both of them are ethers we know we're looking at an acetal or a ketle there's one hydrogen on that carbon so here is the one ether here's the other ether and there's that hydrogen which means we are looking at an acety right right here continuing to go through this molecule oh look at this carbon right here it's part of an ether here and part of an ether here with two carbons hanging off this functional group right here is a ketal so just trying to go through and tell and showing you how to identify it so now if I just put an O down here that doesn't make it an acetal or a Hemi acetal or anything like that because this carbon of the o is not part of an ether functional group what the trend is when we look at a Hemi acetel hemiketal one ether one alcohol acetes ketals a carbon that has two ethers AP part of it the ether functional group is absolutely critical here when we're comparing these right here now in your textbook as you're reading this you're going to start reading about tho acetes thales we're not going to cover that in this class what's whatever um they're very important functional groups but they don't have a lot of translation to biological chemistry which was what we're trying to um get to in this class so right here we just wanted to learn about class 2 carbonal chemistry no good leaving groups and the key things that we talked about were acetes ketals Hemi acetes and Hemi keiles I highly recommend that you go back and watch this video again take notes on it if you have questions please feel free to email me or come to a discussion SL off hour session and I'll be happy to help you however I can I hope each of you are doing good and I look forward to seeing you all soon