Alpha-Beta Unsaturated Carbonyl Compounds

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Alpha-Beta Unsaturated Carbonyl Compounds
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This is the third (and final) quarter of the organic chemistry series. Topics covered include: Fundamental concepts relating to carbon compounds with emphasis on structural theory and the nature of chemical bonding, stereochemistry, reaction mechanisms, and spectroscopic, physical, and chemical properties of the principal classes of carbon compounds. Index of Topics: 00:34 - Typical Reaction with Type 2 Carbonyl 05:17 - Grignard Reagents to Synthesize Carboxylic Acids 10:49 - Summarizing Grignard Reagents, Organolithium Reagents & Cuprates 14:29 - Grignards & Organolithium Reagents do not react with Alkyl Halides 15:54 - Cuprates have their own unusual chemistry 19:12 - Alpha, Beta Unsaturated Carbonyl Compounds 24:53 - Conjugate Addition competes with Addition to the Carbonyl 33:36 - Protecting Groups in Synthesis 41:24 - Designing Synthesis
Computer animation Carbonylgruppe Carboxylate Walking Grignard-Reaktion Lithium Chemical reaction Chemistry Electronic cigarette
Lone pair Hydrogen Lithiumorganische Verbindungen Computer animation Electron Carboxylate Carbonylgruppe Walking Carbon (fiber) Lithium Cobaltoxide
Semiotics Biosynthesis Ionenbindung Kupferorganische Verbindungen Carboxylate Magnesium Electron Carbonylgruppe Addition reaction Colourant Film grain Transformation <Genetik> Active site Lithiierung Exotherme Reaktion Lithium Oxide Setzen <Verfahrenstechnik> Potenz <Homöopathie> Ketone Formaldehyde Walking Carbon (fiber) Chemical reaction Trockeneis Hydrate Water Lone pair Hydrogen Acid Computer animation Functional group Enol Cuprate Chemical compound Proteinkinase A By-product Aage Carbon dioxide Grignard-Reaktion Base (chemistry) Cobaltoxide Catalytic converter Stuffing
Haloalkane Resonance (chemistry) Chloride Chemistry Alpha particle Molecule Electron Addition reaction Lithiierung Sodium borohydride Aluminium hydride Hydride Walking Chemical reaction Alcohol Wine tasting descriptors Acid Cyanidion Yield (engineering) Enol Chemical compound Grignard-Reaktion Chemical synthesis Cobaltoxide Isotopenmarkierung Alkyne Sense District Ionenbindung Kohlenstoff-14 Nitrogen fixation Allyl Enzymkinetik Reactivity (chemistry) Magnesium Carbonylgruppe Alkene Beta sheet Active site Lithium Conjugated system Oxide Setzen <Verfahrenstechnik> Selenite Carbon (fiber) Lithiumsalze Protonation Kupplungsreaktion Water Korken Hydrogen Epoxidharz Gesundheitsstörung Computer animation Functional group Cuprate Covalent bond Proteinkinase A Chemical structure Base (chemistry)
Stoichiometry Haloalkane Regent <Diamant> Chloride Ether Molecule Electron Halogenation Addition reaction Film grain River Lithiierung Silylation Ethane Walking Veresterung Chemical reaction Alcohol Butyl Acid Cyanidion Enol Chemical compound Stress intensity factor Silicon Grignard-Reaktion Bleitetraethyl Cobaltoxide Alkyne Biosynthesis Ionenbindung Carboxylate Ice sheet Chemical plant Copper Ammonium fluoride Methylgruppe Fluoride Reactivity (chemistry) Magnesium Methanisierung Carbonylgruppe Tool steel Faserplatte Lithium Retrosynthetic analysis Pyridine Triethylamin Process (computing) Aldehyde Setzen <Verfahrenstechnik> Grading (tumors) Alkane Selenite Bromide Ketone Carbanion Calcium hydroxide Carbon (fiber) Water Hydrogen Gesundheitsstörung Computer animation Silicon tetrafluoride Functional group Radical (chemistry) Cuprate Dehydration reaction Nucleolus Catalytic converter
so you should be nearing the end of working problems in chapter 21 if you want to stay ahead and you definitely want to stay ahead because everything in carbonyl chemistry builds upon what we've already learned and that's seven weeks of carbonyl chemistry so you don't want to get behind any questions before we get started alright so we left off last time talking about grignard s-- we had returned your reagents and we asked the question to grignard to react with carboxylic acids and we said no because the first thing that's going to happen is an acid-base reaction to deprotonate the carboxylic acid and that grignard is not powerful enough to add into the car box car box lengths okay so but we said lithium will so this is what it looks like when you use lithium instead alright so same first step as a grignard I don't know why it's doing that sort of thing there that's annoying right
okay so first step here we're going to deprotonate the carboxylic acid right so we grab the CITIC hydrogen and then we push the electrons up onto oxygen to give us a carboxylate grittier to are not strong enough to add to a carboxylate but lithium reagents are stronger nucleophiles and they are strong enough to add to a carboxylate so that's what's going to happen arrows
going to come from the carbon lithium bond we're going to attack the carbonyl carbon kick electrons up onto oxygen so notice I'm throwing electron lone pairs bukchon pairs on the oxygen let's take a
look at the tetrahedral intermediate we get and see if we have any leaving groups do we have any leaving groups no tetrahedral intermediate has no leaving groups so therefore it's going to stop here and then what happens is you add water in a second step and you're going to protonate both of those oxygens I'm not going to show that arrow pushing for that ever you're gonna protonate both of those oxygens you can do that this compound right here is typically unstable it's a functional group that's a new one that we're gonna learn in chapter 21 and it's called a hydrate it's an unstable hydrate in fact we will talk about unstable hydrates in on in Monday's lecture so real soon you'll know what that is and so that's why I have it in brackets and it's kind of like an enol keto tautomer ization this is a hydrate and it can and what it what it does is its converts into a into a ketone so we have a long arrow it's not a totalization it's something different but it's going to easily convert in the presence of a trace of acid or base it will convert into a ketone so notice that overall transformation this overall transformation converts a carboxylic acid into a ketone so you want to keep that in mind so far that's
the only way that we can help we have to do this so result synthesis of ketones from carboxylic acids so may want to have that on one of your index cards way to take a carboxylic acid directly into a ketone there's other ways to do this but this is the certainly the quickest most straightforward way to do it all right a clever reaction using grain yards can actually be used to synthesize carboxylic acids so and we use a grignard for this and so what happens is arrow comes from the carbon magnesium bond we attack the carbon of carbon dioxide squish electrons up onto oxygen so notice I'm throwing the lone pairs on that oxygen so there's your carboxylate and then when you add acid in the second step that's looking a little weird here at acid and second step you're going to protonate that and that's a way to make a carboxylic acid grignard into a carboxylic acid would we want to use a lithium reagent for this what do you think yeah we don't want to use the looking reagent cuz Elysium is strong enough to add to this carboxylate so we may have side products if we use a little tiem so this is typically you used using a grignard in the 51 laughs I don't think they do it anymore but they used to do a lab where they would you would make a grignard and then this is really cool because in order for the co2 you can just pour your grignard right over dry ice it's all you know because it's really exothermic reaction but it's kind of cool and you can make carboxylic acids so I don't think they do that anymore I think they do a different one but it's wrong a really fun reaction so the other thing I want you to notice about this because we're building up carbon skeletons if we take if we look at the original grignard that we have let's circle it and let's follow it through notice that we've added on a one-carbon piece we haven't really had a way to do that before so this adds on a one-carbon piece so if you want if you have a carbon skeleton and you need to add one carbon this could be a way to do that okay so I want you to just kind of take a note of that and you should be working on a carbon carbon bond forming on page here and this would be on that adds a one carbon piece another way to add on a one carbon piece from a grignard is used formaldehyde another way if we took this and we did step one formaldehyde I'm kind of squeezing this in here I just thought of this right now step two h2o that also adds on a one carbon piece let me scroll down a little bit we can add it right here all right so see that let's indicate what we started with here let's circle what we started with there's that there's that this is also a one-carbon piece it's just in a different oxidation state so which way you use will depend on what you want to do later if you or what you're trying to make here okay so we've got a two-carbon piece by adding an epoxy ID and we have a one carbon piece now by adding co2 or formaldehyde so just keep that in mind questions so far anybody yes yeah I mean I said they could be interchangeable but water is not going to if you look if you write out the acid-base equilibrium it's not going to be enough to protonate that okay so you have a carboxylate let's write that out good question why I used acid instead of water you are curious about that right let's write it out you know we have acid-base equilibrium we can always write out the acid-base equilibria and see if that's going to be a good enough okay so there's our acid-base equilibrium carboxylic acid plus hydroxide right PKA and let's change color so you can see this a little better I'm adding all this extra stuff and I didn't leave myself enough room here um this is a pKa about 5 correct and this is PKA about 15 so you see how it's favored the other direction so that's why use a stood for this one okay more questions all right thank you for pointing it out by the way all right let's summarize grignard reagents organolithium and cooperate so we're going to add a few new things here at our summary so grignard reagents are again a lithium extremely strong basis powerful nucleophiles that add to all the types of carbonyls we've talked about and Epoque sites so good old Epoque sides they add to epoxy sites because they're strong bases you can't make green yarder again with your each term compounds that contain acidic hydrogen's and since organocopper reagents or cuprates are made from organolithium you they also can't be made from things that contain acidic hydrogen's so here are some examples of acidic hydrogen's so you so you you you can't make grignard x' with compounds that contain these groups can't make a grignard ya organolithium or organocopper reagent from compounds that contain these groups easy to forget but something that you really want to keep it on your mind here in addition there's we also have some
more limitations because green yards can't read because green yards react with carbonyls and up oxides you can't make a grignard reagent out of a compound that has a carbonyl or an epoxy ID in it because it will self react so here's possible grignard reagents in the left-hand side notice we don't have any groups that are going to be reacting here's impossible grignard reagents what's wrong with this one it has an acidic hydrogen right here what's wrong with this one and that's why I have it in brackets because you can form it but it's gonna self react this one has a carbonyl grignard attack carbonyls so you can't make this a stable compound this one has an epoxy I'd you can't make a grignard from a compound that contains an epoxy so you can't do oxides carbonyls acidic hydrogens we are very limited here what's going to happen if we do we make this I have it in brackets it's going to react with another molecule of itself so that's what I mean by self react so arrows going to come from the carpet magnesium bond and it will grab a hydrogen here so you will get this compound right here and methanol all right the same thing happens with a grignard that contains an epoxy it will self react so it's going to come in it's going to tack the least substituted side we're going to kick electrons up on the oxygen so you can't stop these reactions from happening all right so things like that are gonna happen and that's gonna react further so I'm just I'm just drawing that as an intermediate that's going to react further so we'll put that in brackets so it can't make so I hope I made the point you got to avoid these types of groups when you're making grignard reagent reagents greater ground and the other thing that I want to point out that some people try to do on tests is the react Grenier done Organa lithium's with alkyl halides conceptually it should work we have an electron rich grignard we have an alkyl halide is an electrophile and so this is the concept here should work it's definitely sound chemistry to imagine that that would work but it doesn't work it would be nice if it would work but it doesn't work there are very few examples in the literature where there's people have tried to do this it doesn't work very well there are low yields and there's other ways to do it so I don't want you to use it it's not it's not a good reaction okay so no no organolithium reagents reacting with alkyl halides now the truth of the matter is that cuprates do react with alkyl halides this is called a coupling reaction and we are not covering that reaction and so I don't want you using it and the reason I don't want you using it is because you don't know what the limitations of the reaction are so cuprates do work in this way that we've just shown here but I don't want you you won't get credit if you use it on the test because you don't know what the limitations are you don't know the conditions we haven't talked about that reaction so we're just not going to do any organolithium reagents with alkyl halides alright so so basically grignard zin organolithium go together and they have the same reactivity cuprates have their own reactivity so whatta cuprates do we've already seen one reaction with cuprates what was that cuprates don't react with some carbonyls except for one carbonyl it was that which was that one acid chlorides okay so cou pots do react without Keneally's to produce but we're not going to be covering this so you're not going to use it they react with the pop sides acid chlorides and they also do one for addition which we're going to talk about in the next section so Epoque sides so cuprates Epoque sides acid chlorides and what we call one for addition those are the only reactions we're going to do with cuprates the coupling reactions not covered in this book not covered in this class so epoxy sides acid chloride let's give an example of an acid an epoxy side reaction oh my gosh I'm sorry to turn my phone off isn't it nice to know that you're not the only one let's just turn that off how about that my kids usually know that I'm in class right now so they won't call me but that is that didn't happen this time okay we're opening up the epoxy ID after protonation gives you an alcohol so cuprates will do that so cuprates Epoque sides as a chlorides and one for addition which we're going to talk about in the next section all right and you know what I do want to label this here don't use on exam all right so we're gonna move on and talk about alpha beta unsaturated carbonyl compounds in one two versus one for addition we've seen one two versus one for addition what chapter was that in do you remember chapter 16 we had kinetic and thermodynamic right this is the same thing all right so alpha beta unsaturated carbon compounds are usually reactive double bonds the beta carbon atom is electrophilic as it shares the partial positive charge of the carbonyl compound through resonance let's just draw it draw resonance structures for this compound you'll see what this is coming from so with any carbon EO we can take and break a lot break the PI bond and move electrons on to the more electronegative oxygen okay and if we do that we get a minor resonance structure but a contributing structure nonetheless so it looks like that and then as you can see this part of the molecule here you might recognize it there's a there's a positive charge here and this is an allylic cation isn't it all right so whenever we have a Lula cations we can draw a resonance structure for that so we could push electrons here and if we do that we get this resonance structure so you can see that we have two electrophilic sites in this molecule because of that double bond that's conjugated we have an electrophilic site here we can and that's where we can attack the carbonyl electrophilic carbon of the carbonyl we we can also attack here and if we count this is one two three four so if this is the witness would be one two one four position and this would be one two so we start counting from the oxygen this is would be one two we can attack have nucleophiles attack here we can also have them attack here that is the beta carbon so let's label that so that when we have when we're talking about carbonyls alpha to the carbonyl right here adjacent immediately adjacent and then as we move out it's it's a beta so electrophilic center here and electrophilic center here alright so it turns out we have two two places for the nucleophile attack and it can actually do both of those attacks let's look at one to addition we're most familiar with one to taste one to addition that's what we've been doing this entire chapter into one to addition we attack the carbonyl carbon and we move electrons up
onto oxygen just like that so into one two addition we attack the carbonyl carbon just like we're used to seeing and then after protonation let's put hydrogen's here sorry about that our product is an alcohol and that's also one to addition so carbonyl attack at the carbonyl is one two or a nucleophile can attack at the one four position at the beta position and this is what that would look like nucleophile comes here so pretty fancy arrow pushing we're attacking at the beta position we're moving electrons over and making an intermediate that has a functional group that you may recognize if that oxygen was protonated we would call that an enol right when that oxygen is deprotonated we call that an enolate ion okay so this is there's the enol word but eight means it's been deprotonated enolate ion so that's an intermediate in one for addition and then when we protonate we get the nucleophile that it's bonded to the beta position and we regenerate the carbonyl so if you remember back to chapter 16 the one to product was was that the kinetic or the thermodynamic that was the kinetic product and it's going to be the same thing here one two is kinetic and one four is thermodynamic it doesn't look like that would be the most stable product if we're comparing an alcohol versus the carbon EO what's more stable carbonyl is way more stable okay so that's that's actually the thermodynamic more stable product that's the kinetic product okay but attack at the carbonyl is always going to be faster so we have a competition here and when we have a competition you're going to be asked to determine what the product is going to be from that competition and so as you can see here just to summarize here we have the nucleophile can attack the carbonyl carbon I'm not going to finish the arrow pushing or the nucleophile can attack one for it's going to attack it the other electrophilic Center which would be right there if it attacks in the one four position so so one for addition also known as a KA conjugate addition gives the more stable product and the more stable product is always going to be the thermodynamic product and over here attacking one two so this is 1 2 addition is faster it's faster to attack the carbonyl carbon and so that's the kinetic product did I say oh I okay thank you let's fix that alright so how do we know what's going to be faster what's it helpful we know that what's going to be faster than one tooth Bastyr how do we know the product that we're gonna get it turns out that when we use the strong nucleophiles that do an irreversible carbonyl addition which is all our reagents in this chapter right hydride reagents grignard organolithium do cuprates attack the carbonyl only if it's an acid chloride right so cuprates don't attack the carbonyl so when nucleophiles that undergo irreversible carbon additions are used the carbonyl addition product is usually observed carbonyl addition or the one to product these are all very strong nucleophiles so grignard organolithium lithium aluminum hydride sodium borohydride deprotonated terminal alkynes these are all really strong nucleophiles with a with the reason they do irreversible addition is that once they've attacked they can't come back off again and since carbonyl addition is faster does it make sense that we're gonna get the one two product because they're gonna morph it or they're gonna rapidly attack the carbonyl and boom once they're on they can't come cap back off again so it's the one two one two product that we're gonna isolate these guys here when nucleophiles that undergo reversible carbonyl additions well we haven't really talked about those yet we'll talk about those in in chapter 22 in chapter 23 so the reversible carbonyl additions that's chapter 22 in chapter 23 our use the conjugate addition product is observed so we get the one so it's a conjugate addition or one for product all right so if you look here we've got this we also we have the conjugate base that we have cyanide ion and these are milder nucleophiles not as strong and if you look at this the pKa of the conjugate acid well people know a PK it's already the conjugate base pKa of the that's what I want to say sorry conjugate acid is about nine so that could act as a leaving group so all of these nucleophiles are doing the due reversible addition they are going to attack the carbonyl faster but they can come back off again and eventually periodically it will attack the one for position and once it attacks at one for position you form the most stable product and it doesn't go backwards so every nucleophile is going to attack the carbonyl faster it's just that these once they can attack come right back off the the the one that's different is cuprates cuprates are not attacking the carbonyl so they're going to attack one for instead all right so cuprates there's there's our one for addition only one for addition now let's say what if you had an alpha beta unsaturated acid chloride what would where would the cooperate attack I don't know what it do carbonyl faster probably okay so that would be the difference I won't give you that problem but most of the time cuprates don't attack carbonyls so questions so far let's and then we'll look at some examples anybody questions we're going to come back to the same reaction in chapter 22 in chapter 323 so let's let's just look at some reactions here so alpha beta unsaturated carbonyl so now you see where we got the name alpha beta we talked about those when we talked about spectroscopy so conjugated carbonyl lithium aluminum hydride does irreversible carbonyl additions so once it attacked the carbon eel which is faster it can't come back off again so we're going to get one to addition here no one for addition and then when we add water in the second step we're gonna protonate product is an alcohol so all reagents in this chapter
except for cuprates are going to do one two addition that makes that easy so this is one two addition product cuprates on the other hand now remember cuprates have different reactivity I'm doing arrow pushing that really isn't correct but it's just a way to conceptualize what's happening here coupe Regents involve radical chemistry so but we're not going to do that here but it's oh and look what I started doing I started attacking the carbonyl and we don't want to attack the carbonyl because we are attacking one four with cuprates so arrow comes here from one of these carbon coupe copper bonds we attack it whoa nothing there and then we're going to push electrons all the way up onto oxygen we're gonna make an enolate ion we'll talk more about you late ions when we get to chapter 23 and then when we protonate electrons on oxygen are going to come down and we're going to grab the hydrogen from water that is the one poor edition product questions on 1 2 vs. 1 4 addition anybody all right we have one more section and protecting groups and synthesis and then we're going to do some synthesis problems here protecting group of converts a reactive functional group a new group in Newark to the conditions of a desired reaction it it's important in synthesis because molecules of biological interests often we take multiple functional groups they can cross react so for example let's say we wanted to do a grignard reaction where our desired reaction is to have this methyl magnesium bromide grignard reagent attack this carbonyl alright it wants to react with the ester that's the plan to make this compound River it's going to add twice we're gonna make a ketone that's gonna add again what's the problem here acidic hydrogen the acid-base reactions are faster okay so we have an acidic hydrogen alright so protecting group is going to allow us to make just do this reaction by protecting that alcohol all right so let's draw what have actually happens and then we're going to do and then we're gonna fix it so here let's draw this compound so these acid-base reactions very very fast so we get that and what's our other product methane ch4 ch4 gas which bubbles off and there there's no reaction now that has happened because of that acidic hydrogen we've just quenched our grignard it's no longer there all right so um so what we can do is protect the alcohol there are hundreds if not thousands of protecting groups we're going to learn to one in this chapter and one in chapter 21 and those are the only two that you need to know all right we're going to use a common alcohol protecting group as a silo ether and this is the only silo ether that we will use there's other silo ethers there's tri methyl silyl this is tert-butyl dimethyl silo our tbdms and you can feel free to use this abbreviation tbdms ether and so here's what the here's what it looks like we're going to use tbdms and i think your book uses triethylamine and you certainly can use triethylamine i'm just gonna use pyridine instead because you're already familiar with triethylamine and there's a lot that we need to remember here so this or or pyridine I'm going to use pyridine only all right so what you're essentially doing is you're deprotonating the alcohol is attacking the tbdms and then you're going to be deprotonating it so it makes a silo enol ether a silo ether all right so how let's make our synthesis work now so we're going to protect that alcohol and then all the other things that we plant are going to be able to work very easily I think your book also uses a middle we're going to just just to make this a little bit easier for you I'm going to use pyridine because you're used to using pyridine tert-butyl dimethyl silo chloride and pyridine so we have our oxygen bonded to silica silicon and then we have two methyl groups okay tert-butyl dimethyl silyl ether now we can do our reaction ch3 MGB our excess because it's going to add twice followed by water okay got it there's our reaction now we need to take that group back off again right and you take that group back off again we call that D protecting here's the reagent that you're booked to use this tetra butyl ammonium fluoride sorry about that okay what are we doing here fetch a butyl ammonium fluoride or you can use acid PKA has to be less than two so pretty strong acid so that's on the top of the next page try Elko Sylar Eaters are stable from pH 2 to pH 12 D protect with strong acid or f- YF - the silicon fluoride bond is the and this would be si here not s the silicon fluoride bond is one of the strongest Sigma bonds known so let's compare what happens when we add fluoride here SIF 139 K Cal's per
mole silicon oxygen bond 88 K Cal's per mole so I'm using fluorine is a great way to do protect questions on using a protecting group in synthesis so that's our protecting group for alcohols we're only going to use that for alcohols in chapter 21 we're going to talk about a protecting group for ketones and aldehydes those are the only two we'll talk about in this class alright so let's do a little synthesis here so we've done a lot of so we did a lot of synthesis last course most of this in synthetic design and here but we're are we getting to the point where there's many different ways to synthesize compounds so that gives us a harder job over grading exams so if you ever synthesize something and you get it marked wrong and you think it's right come up and show me and all I'll tell you if it works or not okay so we got a lot of different great creative lines out here so you guys are going to come up with your own own ideas here and very often a student show me a synthesis that's actually better than the one that I've shown on the board and I like when that happens okay so you guys have some great creative ideas all right so let's say synthesize the following compound from the given starting material you can you go in the forward direction or you could go in the reverse direction working backwards from the product if you work backwards from the product that's retrosynthetic analysis I never make you use retrosynthetic analysis it's a tool for you to use and it can be very helpful when I'm grading a synthesis on the exam I grade the synthesis in the forward direction though because it's difficult to grade people's thought patterns so that we try not to do that alright so what we're noticing here and you want to get in the habit of counting carbons we're actually adding a carbon here so we're making a new carbon-carbon bond here so since we're making a new carbon-carbon bond you want to use carbon-carbon bond forming strategies so that so that would be use carbon nucleophiles we have a number of carbon nucleophiles we have grain yards organolithium we have cuprates we have deprotonated terminal alkynes right so this is why you want to have a sheet that has all your carbon-carbon bond forming strategies we also have cyanide ion right if we use if we do an sn2 with cyanide ion that also adds on a carbon okay so so think of these carbon carbon nuclei nucleophiles so grignard organolithium etc so we've got a lot of things to do here so what I'm thinking here retro synthetically is doing a dehydration after making having this compound here so use one of the carbon nucleophiles attack the ketone make an alcohol and then do a dehydration so once I have this I would do h2 so4 concentrated for dehydration and this I can make from my starting material so you know when we go where we go backwards you keep looking back at your starting material you're trying to actually work towards that starting from the starting material methyl magnesium Program bromide or methyl lithium okay so here's what the synthesis in the forward direction would look like so so sometimes I will have an open-ended synthesis where I ask you to draw the products from each step and that's what this would look like sometimes I have it in a box and I just have you number the steps so I do both types if it was an open-ended synthesis where you have to fill in the reagents and draw the intermediates it would look like this these of course are more difficult to grade so I can't put too many of these on an exam or we're there all day and all night grading okay so grignard attacks the carbonyl and then we protonate and then we just use h2 so4 concentrated to make our product questions on how I did that anybody so it's a little trickier now to figure out what to use so we do have one more than one way and but now the synthesis is going to get more complicated because we're building up elaborate carbon skeletons alright so here we go here I'm looking at the product and I'm going to go in Reverse here and I'm noticing I'm counting carbons and I'm noticing that I have a new carbon-carbon bond so I'm going to use some of the new carbon-carbon bond forming strategies that we've learned so green yards organolithium x' cuprates not as much they're more selective in what they do but what I'm thinking is I'm adding on a one carbon piece like we mentioned earlier if I had this if I had this this compound here which I can make from alkyl halide and lithium if I do if I have that and I add on a one carbon piece remember we talked about two different ways to add on a one carbon piece using formaldehyde or co2 those are ways to add on a one carbon piece both add one carbon and I'm going to show the synthesis from both of those does not matter which one you use both add one carbon ok and how do I make the how do I make the alkyl halide I can make that from my starting alcohol and pbr3 pyridine all right so I've got the plan and now I'm going to write the synthesis in the forward direction and I will branch off here because you can do use both of those reagents one's going to take one step more that doesn't matter to me all right I want to convert our alkyl group into alkyl halide pbr3 purity and that's one of those famous reagents that we're going to use a lot we use a lot all year long so that converts that into an alkyl halide then we write lithium here I know I'm not worried about stoichiometry here so you can just write Lew theam here that's fine so now we've had our Daniel lithium reagent could we make a grignard instead absolutely we can make a grignard instead doesn't matter probably should make a grignard instead right you seen a problem here if we make they're gonna lithium with co2 we do that we go immediately to our product with one carbon or if we do co 2 followed by acid we'd be better to use a grignard for this method because remember lithium can add to the carboxylate once you form it so really better to use a grignard if we're going to use that method and then but that's
our stopping point so we'll talk more about that next time think about why you would want to use a grignard instead with co2