hello organic chemistry students in this video we're going to be talking about class three and the final class of carbon yield chemistry groups now when we think about class 1 and Class 2 how are they defined class ones are carbon yields that have good leaving groups on them class two are carbon yields that do not have any good leaving groups on them and that's the basic distinction between class one and class two now class three I don't want you to consider it as a totally separate one because class 3 can be present within class one and Class 2 I know that sounds crazy but let's see if I can explain this a little bit in more detail so here is a carbon yel right here with a carbon attached to it so this could be an aldhy possibly if this R group was a hydrogen that's an aldhy if it's a carbon it's a ketone now the Z group right here means it could be an O an O carbon chain or an anti hydde or any of the other class one carbonal so class 3 is not talking about the carbonal itself and the leaving groups on it it's talking about the carbon directly attached to the carbonal which is called the alpha carbon so any carbon directly attached to the carbon yal is termed an alpha carbon and the hydrogens on an alpha carbon are acidic why if we use a base a base can come in and pull one of these protons and we put electrons on this carbon which seems like a bad idea carban not so hot but what makes this carban so stable the lone pair is on a carbon directly attached to a carbon oxygen double bond resonance can occur so the negative charge can donate down and break open the double bond and we're putting the negative charge on oxygen so it's going back and forth back and forth between these two states and that's what's stabilizing it so anytime we have a carbon yield we have the potential of having a alpha carbon there's only going to be one example where you will not have an alpha carbon in a molecule and that's if you have a carbonal and you have maybe two chlorines attached to it or you have a carbonal and you have two hydrogens on it so there's just no carbon directly attached most things though have Alpha carbons that's the important thing to take home here now we're going to talk into what type of bases are going to be used to pull these protons and what can we do with this these systems right here now these systems right here are called enolates now both of them get the name enolates but we're going to break this down into which one is the more reactive intermediate when we I shouldn't say intermediate the resonance form when you look at this oxygen with the negative charge oxygen the second strongest electronegative atom on our planet versus carbon which is an Electro negative at all which one's more unstable with the negative charge and that's the carbon right here so in this form with the carbon being negative this is the nucleophilic state of an enolates this is going to be the state that's going to do all the chemistry that we're going to talk about the other one right over here isn't going to do anything it's going to be relatively chemically inert for what we're going to be seeing in this class so now what type of bases can pull this proton we can use put a little arrow down here I'm going to circle bases we can use hydroxide bases we can use sodium hydride we can use sodium amid we're going to use pretty much any base that we've seen in genem and organic chemistry the most common ones we're going to see are going to be the hydroxide type bases and another one called LDA now I'm not going to go into the full chemical structure of LDA but all you have to know is that LDA is made of a lithium and then a base component that has a negative charge on it and it's this negative charge right here that pulls those protons and if you're dire to know what this actually looks like it is a nitrogen with an is two isopropyl groups and two lone pairs thus the negative charge so that's what it is right there so the abbreviation LDA stands for lithium o lithium Di isopropyl amid right there now you might be saying wait why is that an amid it's okay we don't care about it it's mostly because the nitrogen has that lone two lone pairs on it and a negative charge that's what gives it its characteristic amid State all we care about it's a base and it pulls the alpha proton let's go ahead and see what we can do with these molecules I shouldn't say these molecules but this chemistry so I'm going to go ahead and do this with an aldhy functional group first so here's an alahh and I'm going to treat it with sodium hydroxide and this carbon chain with a chlorine on it now the sodium hydroxide will come in and it will pull one of the alpha protons not both of them just one so we pull it and I'm resonating electrons all the way through that carbon yel so I'm showing the resonant structure that we showed previously right here but I can also show the resonant structure right here so in both cases we're showing both resonance structures of this molecule of these two the one on the left or the one on the right which one is more nucleophilic having the atom with the most unstable negative charge and that's the one on the the right right here because the negative charge is on carbon so now if we enter in this three carbon long molecule with a CL minus on it haven't we seen chemistry where a nucleophile could attack this carbon and displace the chlorine much like an sn2 reaction we did the negative carbon right here can attack this carbon's antibonding orbital push the chlorine out and what do we get get at the end of this reaction we have just alkal that looks a little odd oops that looks a little odd so let me just draw it this way we've drawn this alkal carbon species so using the chemistry of the alpha carbon we can add carbon chains and make bigger and batter molecules now if we wanted to we could repeat this chemistry again and what we will get out is two propy groups on that carbon now no more chemistry can happen on this because the alpha carbon has no more Alpha hydrogens we need the alpha hydrogens to do this but this is a nice way of showing how we can do alkal on these carbons now while this is very important for synthetic chemists what I want to get into is to talk about why do we care about this in terms of biological chemistry that big exhale you just heard CO2 coming out of my lungs right it's coming from a process called decarbox ilation about 70% of all CO2 comes from this process and it's coming from systems that have carbon yields in them and by the end of today's lecture we're going to see where some carbon dioxide comes comes from the metabolism in our body so now the chemistry that I've just shown you right here if I go ahead and Shrink this down is pretty much the chemistry that we're going to see in this video today nothing different what I'm going to do on the next slide going to go ahead and open that up is we're going to talk about some chemistry called aldol chemistry what it means and how we can predict things let's go ahead and get right into it all right so on this slide like I just said we're going to talk about alol chemistry now aldol chemistry is going to involve either aldhy or ketones now this should sound familiar if we remember when we're talking about class 2 carbonal we talked about Hemi keiles Hemi acetes acetes and kiles wasn't the chemistry for aldhy the same as ketones and ketones and alahh it was they were identical to one another and that's going to be the same thing here with aldol chemistry so I'm going to go ahead and show that same alahh again but now I'm just going to put an R Group in where it could be a hydrogen for an aldhy or a carbon chain for a ketone if I treat this with n what we're going to get as our intermediate is this carbonal species right here and if I now write then this alahh notice it's a different length of alahh here we have 1 2 three carbons here's one and two we form a negative charge on this carbon and now we have this aldhy right here this negative charge will attack this carbon because oxygen is partial negative this carbon is partial positive and we break open the double bond when that happens we have now just added that two carbon long molecule of that aldah and this is what's called the alol addition now once again this can be done with an alahh or KET and we can intermix them we don't have to have an alide here we can use a ketone we don't have to have an alide here we can use a ketone or we could use two ketones the arrows are the same what's always going to be the product from an aldol addition a carbonal attached to an alpha carbon and the carbon directly attached to it which is called a beta carbon we have an O on it so what we get from this we're always going to see a beta hydroxy that's the O group carbonal I'm going to abbreviate carbonal just like this that's the alol addition now we can take aldol additions and do further chemistry called aldol condensations that's not relevant in this class our bodies do not do this in great Pathways or the pathways that we're going to be seeing here in the next couple of weeks all we care about is the aldol addition so let me go ahead and put a box on this so that's with an alahh and a ketone what if we started with a class one carbonal let's say an Esther could I take this Esther and treat it with a base I could and what we will do is we will deprotonate the alpha carbon and we form a negative charge on it what if I wrote then this I'm going to put in we'll do one oops excuse me we'll do one carbon again we'll form this Esther right here this negative charge should attack this carbon of the carbon yield the Esther break open the double bond but wait a second this is an Esther so do we have good leaving groups we do the negative charge will donate back down and we kick out the carbon chain and what we get at the end of this reaction is here's our Esther and we've added in a beta Ketone so when we start off with a class one carbon yield group and do the same type of chemistry as an alol we end up with a beta carbonal or beta Ketone carbonal species this is going to be important for decarbox silation in our bodies now before we get there I want to talk about these reaction conditions in a little bit more detail so here I'm saying sodium hydroxide so we pull this proton we form the negative charge and then we add in the next alahh species what if I didn't want to do that what if I wanted this molecule to react with another identical aldah or Ketone functional group how could we do that let's go ahead and move this up and we'll address that right now so what I am asking is if we start with this three carbon long chain and I'll put an alahh in and I would like to form this system right here where we have 1 2 3 1 2 3 so two of these aldhy react in an aldol condensation now you might be asking but wait what's the name of the reaction with the um Esther species or an amid up above those are technically called claz and condensations but for this class all I care for you to know is that they're aldol like reactions that's it so if I want to do an aldol reaction with the same exact aldhy I need one aldhy to become an enolate and the other one to remain as is so if I just throw in sodium hydroxide that means there's a whole bunch of Base and I'm going to pull all these protons right here excuse me right here but I don't want to do that what I'm going to do right behind it is write 0.5 equivalents ah going back to our alkine chemistry if I only have a half of an equivalent of sodium hydroxide do all of these get their protons pulled no so what we have in solution is we have half of them deprotonated and the other half still intact so the ones that have the negative charge will attack this alahh break open the double bond and form our aldol addition product right there now like I said before we can do things called aldol condensations we're not going to talk about that in this class whatsoever just the alol additions so we just previously on the other slide talked about adding on carbon chains so that's just alkal like in fredal crafts alkal this is just aldol alkal we can do reactions between carbon yields and that's called the aldol reaction right there alol addition to be specific what I'd like to do next is talk about where carbon dioxide comes from and why this matters all right so right here we're starting off with this Esther species treating it with LDA which is oh wait one of those bases that we talked about on the first slide and we're going to deprotonate one of the hydrogens on this Alpha carbon so what we're going to have in solution is a negatively charged carbon now all of them are pulled because we don't have an equivalent control behind it and we definitely don't want that here we want to pull all of them what we're adding in next is this acid chloride which is a Class one carbonal so we can attack that carbonal break open the double bond electrons donate down and we kick out the chloride and we form this beta Ketone Esther species so a beta Ketone relative to this carbon yum same exact thing that we saw in the previous slide starting with the class one functional groups so here I'm showing you how we can mix and match them we can do class ones class twos and stuff like that here they're both class ones which is very nice so now I want to take this molecule right here and just bring it down below this is going to allow us to do a little bit of review chemistry from our class one carbon yals if I take this and treat it with H+ and H2O what happens to an Esther under H+ acidic conditions HCL and H2O the Esther becomes a carboxilic acid what happens to the Ketone nothing we can form a hydrate but nothing happens in that hydrate and it goes back to the Ketone form so now we have made a very subtle change over here we have a beta carbon y relative to an Esther we now have a beta carbonal relative to a carboxilic acid I'm going to go ahead and erase this hydrogen and I'm just going to make it a little bit longer just like this and let me go ahead and bring these slides up all I'm going to do next for the next reaction step is add in a little bit of heat heat is going to make that carboxilic acid more acidic and what is going to happen when it becomes more acidic is is that proton is is going to leave on its own we have a negative charge H+ is floating around in solution so now that negative charge will donate down into resonance resonating through this carbon yal now because we have this beta carbon yal right here something unique is going to happen instead of just having resonance the negative charge will donate down and we are going to break a carbon carbon Bond and put electrons on this oxygen right here this carbon carbon bond has been cleaved and that's something new we haven't seen that yet in this class and what we liberate is CO2 gas and in this Liberation right here what we have now formed is an oxygen with a negative charge and this carbon species this negative oxygen can pick up this proton that's been sitting around in solution and we now form an O on a carbon carbon double bond which we know very well under goes tariz to form this species right here what have we just done we've taken the Esther transformed it into a carboxilic acid and with the addition of Heats forced a decarbox reaction that allows the liberation of of CO2 from our starting material decarbox reactions only occur when you have a carboxilic acid and a beta carbonal this will never work if you have an alpha carbon yal because if there was a carbon yal here we can't resonate those electrons through an alpha carbon yel only through the beta carbon yal and that is the essential part that we want to know about in class three carbonal chemistry this decarbox process and we're going to see how this is going to help power the kreb cycle in forming electron carriers which go down to the mitochondria present in the mitochondria to help form ATP adenosine triphosphate or muscle contraction or for you rolling at your eyes as you are listening to these videos right here so this right here is our class 3 carbonal chemistry as always I recommend going back watch them again or watch the video again and take notes over them if you have any questions please feel free to email them to me or come to our discussion section or my office hours and I'll be happy to answer any questions that you have I hope each of you are doing well and I look forward to seeing you all soon