Addition of Organometallic Reagents to Carbonyls

Video thumbnail (Frame 0) Video thumbnail (Frame 1614) Video thumbnail (Frame 7286) Video thumbnail (Frame 9213) Video thumbnail (Frame 14718) Video thumbnail (Frame 24091) Video thumbnail (Frame 33464) Video thumbnail (Frame 40026) Video thumbnail (Frame 51320) Video thumbnail (Frame 62614) Video thumbnail (Frame 73908)
Video in TIB AV-Portal: Addition of Organometallic Reagents to Carbonyls

Formal Metadata

Title
Addition of Organometallic Reagents to Carbonyls
Title of Series
Part Number
5
Number of Parts
27
Author
License
CC Attribution - ShareAlike 3.0 USA:
You are free to use, adapt and copy, distribute and transmit the work or content in adapted or unchanged form for any legal purpose as long as the work is attributed to the author in the manner specified by the author or licensor and the work or content is shared also in adapted form only under the conditions of this license.
Identifiers
Publisher
Release Date
2015
Language
English

Content Metadata

Subject Area
Abstract
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: 00:26 - Addition of Carbon Nucleophiles 04:54 - Preparation of Organometallic Reagents 11:09 - Organometallic reagents are powerful bases 14:34 - Acidic groups that interfere with Grignard Formation 19:46 - Organometallic Reagents are Powerful Nucleophiles 24:57 - Typical Reaction with Type 1 Carbonyl 31:38 - Typical Reaction with Type 2 Carbonyl
Loading...
Metal Ionenbindung Alkane Carbon (fiber) Electronegativity Volumetric flow rate Computer animation Electron Hyperpolarisierung Functional group Addition reaction Carbonylgruppe Valence (chemistry) Chemical compound Metallorganische Verbindungen
Stoichiometry Ionenbindung Left-wing politics Kupferorganische Verbindungen Species Metallbindung Copper Organische Verbindungen Electron Hyperpolarisierung Lithiierung Storage tank Lithium Metallorganische Verbindungen Butcher Lithiumorganische Verbindungen Magnesium Carbon (fiber) Electronegativity Chemical reaction Kupplungsreaktion Computer animation Chemical compound Covalent bond By-product Grignard-Reaktion Isotopenmarkierung
Metallbindung Hydro Tasmania Chlorine Ether Acetylide Electron Rapid Halogenation Film grain Lithiierung Metallorganische Verbindungen Vinyl chloride Walking Sulfur Chemical reaction River source Hydroxide Lone pair Iodide Acid Chemical compound Grignard-Reaktion Cobaltoxide Alkyne Ionenbindung Biosynthesis Carboxylate Copper Carbonate Fluoride Abbruchreaktion Carbonylgruppe Lithium Conjugated system Potenz <Homöopathie> Grading (tumors) Stickstoffatom Magnesium Carbon (fiber) Ice front Protonation Electronegativity Water Hydrogen Sodium Computer animation Functional group Covalent bond Proteinkinase A Salt Chemical structure Base (chemistry)
Semiotics Haloalkane Growth medium Ether Ethanol Molecule Rapid Electron Halogenation Lithiierung Aluminium hydride Hydride Walking River source Chemical reaction Alcohol Electronic cigarette Acetylene Acid Chemical compound Grignard-Reaktion Cobaltoxide Thermoforming Hydrocarbon Ethylgruppe Ionenbindung Kohlenstoff-14 Phenyl group Reaction mechanism Ice sheet Hydroxyl Organische Verbindungen Carbonylgruppe Active site Lithium Process (computing) Oxide Lithiumorganische Verbindungen Alkane Bromide Magnesium Carbon (fiber) Protonation Hydrate Water Hydrogen Ice Epoxidharz Computer animation Functional group Covalent bond Deuterium
Kohlenhydratchemie Chloride Atomic number Chemistry Methoxygruppe Acetylide Dimethylcarbonat Electron Data conversion Lithiierung Aluminium hydride Walking Veresterung Chemical reaction River source Alcohol Electronic cigarette Lone pair Acid By-product Grignard-Reaktion Cobaltoxide Methanol Isotopenmarkierung Stop codon Ionenbindung Biosynthesis Stereochemistry Reaction mechanism Hydroxyl Organische Verbindungen Reactivity (chemistry) Carbonylgruppe Exotherme Reaktion Acetaldehyde Lithium Process (computing) Chemical reactor Ketone Magnesium Carbon (fiber) Protonation CHARGE syndrome Water Sodium Ice Drop (liquid) Epoxidharz Computer animation Functional group Base (chemistry)
Transition metal Nitrogen fixation Reaction mechanism Carboxylate Chloride Hydrochloric acid Copper Chemistry Methylgruppe Reactivity (chemistry) Electron Shear strength Methanisierung Carbonylgruppe Tetraederstruktur Active site Lithiierung Mixture Metallorganische Verbindungen Lithium Methane Aldehyde Bromide Ketone Magnesium Walking Carbon monoxide Veresterung Alkoxide Carbon (fiber) Chemical reaction Alcohol Water Hydrogen Acid Computer animation Functional group Radical (chemistry) Cuprate By-product Chemical compound Grignard-Reaktion Base (chemistry) Carboxylierung Isotopenmarkierung
Computer animation
all right so we're still talking about irreversible additions to carbonyl compounds and so now we just started last time talking about organometallic reagents where we
we have carbon alkyl groups bonded to metals and because we bond the alkyl groups to metals we change the polarity of the bond so this is what we're used to seeing groups like this where carbons bonded to group that's more electronegative so electrons flow this direction which means carbons partial positive but if we change that to a metal then the metals from the left-hand side of the periodic table are going to have electronegativities lower than lower than this and so the electrons now flowed the other direction making us have electron rich carbon and so there's a bunch of these compounds we're only going to talk about three so we're going
to talk about compounds that have a carbon lithium bond we're gonna have a hit talk about compounds that have a carbon magnesium bond and carbon compounds that have a carbon copper bond so these are the only three that we're going to talk about so let's let's let's check out on electronegativities here and see if we can figure out which of these reagents is going to be more which of these bonds is going to be most polarized and which ones going to be the most reactive so carbon is going to be two point five all the way across for electronegativity lithium is 1.0 magnesium 1.2 and copper 1.8 so if we if we look at the electronegativity difference we can see which of these bonds is the most polarized so let's let's do electronegativity difference here on the left hand side and difference here it's 1.5 here it is 1.3 and here it is 0.7 so you can see that definitely the most our bond is going to be the carbon lithium bond most poor because electronegativity difference is the largest and so that all with that that also means that this is going to be the most electron rich carbon of comparing all three of these species most electron rich carbon so we have electrons flowing towards carbon here but we have the most electron density flowing towards the carbon when we have a carbon lithium bond all right I want to say a couple things because there's a tendency to think of these bonds as ionic bonds are not ionic bonds if you go back to chapter one we sort of talked about the fact that once the electronegativity gets greater than about 1.7 1.8 then electrons are transferred completely and we have an ionic compound but this is not this is the largest difference we have is 1.5 so that is considered to be a carbon lithium covalent bond and so these are these are actually quite different here so about about covalent carbon metal bonds the reactivity towards electrophile depends on the polarity so organolithium are going to be the most reactive greater than organo magnesium greater than organocopper now for the most part we're going to be using organolithium compounds in organo magnesium par compounds interchangeably but there is one reaction where you need a super great electrophile that will work for you know lithium but not work for again on magnesium compounds and that's that's coming up so let's label these certainly and I want you to know this the organolithium are the most reactive and are get a copper least reactive alright so we're going to have
three different organometallic reagents there's organolithium organo magnesium organic knees iam have a special name and that's grignard so they're grignard reagents and this is how this is how you make them we have our X I don't know why that's cut off there it looks like it's a little cut off plus two lithium and you get our li plus Li X so here's an example here okay we're at that with lithium now I'm not going to be worrying about stoichiometry on the exam you can just write lithium you don't have to write to lithium there's your organolithium product and you can leave out store qiyamah tree and side products so I don't care about the sweet stoic geometry and I don't care about the side products all right so that's an example of organolithium compound grignard reaction has a little bit different
structure so we take our X plus mg and we get our mg X so the the halogen that from the Rx actually becomes part of the compound so it looks a little bit different here and and it turns out that you must use a nice or ether solvent for this reaction organolithium don't need to use ether but you definitely need to for a grignard here's an example right here mg ether and your product is mg BR and this is a grignard Green URI agent you can also call organo magnesium but it's definitely much more commonly called a grignard reagent and the ether is there because you actually get something that looks like this where you have your green iord and then you have the ether the lone pairs on that on the oxygen of the ether sort of donating electrons to the magnesium don't need to worry about this but that's this is this is why you need the ether solvent all right organo copper I have a completely different structure also so let's go let's look at that on the next page okay no copper reagents also known as cooperate or Gilman reagents I will call them cuprates because that's how I learned it but there's also these other names their prey theory are prepared from organolithium reagents if I reaction with a copper salt usually copper iodide so here's what it looks like here's what it looks like rx+ to Li gives you there's your there's your lithium reagent right so we do the same reaction we did on the previous page and then you had copper iodide notice you have two are groups here are two culi so the copper stays the luteum stays and that's a cooperate so two steps number one make organolithium number to add a copper iodide okay so that's how you make those let me give you an example and you can use a vinyl chloride for this reaction so this is what it would look like you add the lithium you don't need to put the two in front of the lithium I'm not worried about that then you add copper iodide and you get to our groups bonded to the copper and then you have culi just like that alright so those are the three reagents need to know how to make those those three reagents grignard reagents that form rmgx and you can have bromine chlorine or iodine nonono fluorides here organolithium is our li and organic cooperate is our to see you li need to know that they react as if they were carbon ions they are not true carbon
ions because they have covalent carbon metal bonds however we can think about them conceptually as carbon ions so carbon I would be an ionic compound and these aren't because it's a covalent bond but that's the way they react compare this with sodium acetylide and we have here carbon two point five and sodium 0.9 and this but this guy's actually ionic so it's right on the borderline here it's actually ionic so conjugate base of a terminal alkyne this is negatively charged and then we have any plus they're going to behave in a lot of the same ways but they're not exactly the same because this is an ionic compound so here we have electronegativity differences 1.6 so it's somewhere around 1.6 1.7 is where you start getting into ionic compounds questions so far anybody all right let's talk about reactions of organometallic reagents here are some examples there organometallic reagents powerful bases extremely powerful bases they react rapidly with protons in an acid-base reaction so this is what it looks like here this is an acid-base reaction and we'll draw out the reaction and then we'll see which way the equilibrium is favored so the arrow is going to come from the carbon magnesium bond we're going to grab a proton and then we're going to break the hydrogen oxygen bond very rapid reaction with water so there's the hydrogen that we just added on let me mark that that's the hydrogen right here so you're going to get that plus h o mg BR you can write it like that or you can write it like you get a hydroxide you get an mg 2 plus and you get a V R - okay so that's what happens when you hydrolyze a grignard let's look at the direction of equilibrium so we're gonna look at four conjugate acid-base pairs and what do we have here so we have water and we have hydroxide over here conjugate acid-base pairs right here the one with the extra proton is the acid so here's our acid on this side of the equation and here's our another conjugate acid-base pair here's our acid on this side of the equation this has a pKa of about 15 and this has a pKa of about 50 so as you can see equilibrium very strongly favored to the right so long arrow to the right tiny tiny short arrow and really there is no reverse reaction for this well just write draw out that like write that anyway all right so same thing with organolithium reagents and so you got to be careful with these guys so that you don't have proton sources around if you have proton sources around then you will hydrolyze so proton sources can be water it could be acids any acidic protons so there we just we just put a hydrogen there and then we get a carboxylate all right so it's easy to forget about that but this that's the fastest thing that's going to happen with these guys if there's a proton source they will react with it and direction of equilibrium let's do that again here so here's our acid on this side of the equation here's our acid on this side of the equation this is PKA about five this is PKA about 45 so once again very very strongly favored to their lab to the right so try not to forget that it's really easy to forget when you're doing synthesis we get so caught up in the carbonyl that we forget about these acidic hydrogen's that kind of interfere with what we're trying to do all right so this rapid reaction with water or any protic acid means that grignard reagents organolithium cuprates cannot be prepared from compounds that contain acidic groups if you want to make a grignard and your compound has an acidic group you can't make a grignard from it so here's the city group set interfere anything in here hydro there's as acidic hydrogen right here a hydrogen on a nitrogen here's another city hydrogen hydrogen attached to sulfur carboxylic acid acidic hydrogen even a terminal alkyne hydrogen on a terminal alkyne you can't make great news from these compounds so don't make a grignard a grain yard or organolithium compound from compounds that contain these groups all right so that's super important and very very easy to forget as I can as I will tell you when I grade exams I will see a lot of people forgetting about that all right so here's an example of a failed synthesis this person is trying to make a grignard from this compound
here so remember when we make the grignard the magnesium goes in between the carbon and the bromine bond so we have here mg ether you actually will make a little bit of this but as soon as you make it it's going to be protonated by any acidic hydrogen's that are in the medium so another molecule here definitely so you make that and then any other proton sources and they're there and any of these other compounds here so air comes from the carbon magnesium bond grabs the hydrogen and looks like that and then so what you end up getting is ethanol not what you wanted you wanted to make a grignard out of this compound you're going to get that and you're going to get deprotonated alcohol so you can draw it like this or you can draw this like this with BR ch2 ch2 OMG BR okay you can write it either way but that's what you're going to get alright so that's a big problem that's not a grignard reagent so these guys are the actual products so this rapid reaction with water and any protic acid can be used to synthetically turn an alkyl halide into a hydrocarbon if you use a labeled proton source like d2o you can actually make Deuter deuterated compounds so here's an example right here now we're going to make we have no acidic hydrogen's here so we will be able to make this grignard rather nicely here so the magnesium ends up being going in between the carbon and the bromine and then if you protonate this if you if you actually deliberately add water yuuup rotate that so so that's a way to actually get rid of this bromine in our molecule so that's what you would get if you use d2o instead or some sort of proton source that has deuterium and you'll get CH to D so there's the deuterium let's and let's circle that deuterium from one of these bonds here and now you've made it a deuterated compound and that's just by protonating the grignard once you form it you protonate it and if you use a deuterated proton source you'll get a deuterium incorporating questions so far anybody all right so again a metallic reagents are powerful nucleophiles they're very important organic chemistry they can react with the PAC's ice to form alcohols the result is an extension of the carbon chain by two carbons so what am I talking about let's let's keep an eye on this number here okay so that's going to keep an eye on that we're gonna come back and circle those let me come back all right so we're making organolithium compound so alkyl lithium all right and now we're going to open up an epoxy so this is going to attack it a pop side it's gonna be very similar to lithium aluminum hydride attacking an epoxy arrow is going to come from the carbon lithium bond if this was a substituted aprox I'd it would attack on the least substituted side let's circle that original of group that we started with here's our three carbons right here here's our three carbons right here and you see how I've added on two carbons I've added on a ch2 ch2 Oh - once we protonate that it will be a ch2 ch2 O H and that is that something you might want to tuck away you might see that on a future exam where you have to add on a two-carbon piece that looks like that we're going to talk about other ways to add on to Carbon pieces but this will add on a ch2 ch2 O H - carbon extension where the functional group is on the end okay so we did it we had another two-carbon extension in chapter 11 right where we took acetylene we deprotonated it we attacked an alkyl halide that was also adding on a two-carbon piece okay just different functional groups all right so a good thing to tuck away
we're and so and why not what do you think would be a good idea right now is if you have an index card or a larger index card or sheet where you start to now write carbon-carbon bond forming reactions we have one from 50 once B and we're going to now have a but we're gonna have now we now we have grignard organolithium x' and cuprates here on 451 c so those are great when you're trying to build up carbon skeletons all right longer exertions can be made by using substituted époque sites so here's another example here what side is this going to tech on left or right powerful nucleophile ticks on the Leslie substituted side right this goes back to chapter nine all right so that's what's going to happen here it's going to come and attack on the least substituted side we're gonna kick electrons up onto oxygen that's at the very end of chapter nine if you want to take a look at that and after protonation yeah and there's our phenyl ring so we've added on actually a four-carbon piece where the hydroxyl is in the two position okay so that that's just something to keep in mind here we've added on a one two and then this is three and four if we drew out that Ethel added on a four carbon extension and so just remember that this is of course as strong nucleophile attacks at the least substituted side of the Epoque side all right so gern yards can it can be protonated they can attack up oxides but the the most important reactions that we see with green yards are grignard attacking carbonyls okay so let's look at some examples of that let's look at some examples with type 1 and type 2 carbonyls so here's a typical reaction with a type 1 carbonyl so we have ethyl magnesium bromide or ethyl grignard arrows going to come from the carbon magnesium bond these are going to look just like lithium aluminum hydride okay so we have we're going to do a very similar way arrows going to come from the carbon magnesium covalent bond we're gonna attack the carbonyl carbon we're gonna kick electrons up onto oxygen so this will look really familiar to you it looks just like the mechanism for the lithium aluminum hydride with the type 1 carbonyl except rather than transferring a hydride we're actually transferring an alkyl group oh so we're building up carbon skeletons but still the same thought process in that we have tetrahedral intermediate with no leaving group therefore it stops here until you add acid in a second step so really key here is that we want to have the water in a second step what happens if we mix the grignard and the water what's the going to happen we're gonna you're going to kill our grignard reagent a word that you'll hear used as we're going to quench it it's going to you're going to kill that because the acid-base reactions are going to be faster and so then our grignard will be gone and then we don't get anything that we want so add water in a second step
but Messing's mechanistically very similar to lithium aluminum hydride alright question about reactions with type 1 carbonyls anybody alright so we can agree organolithium same like I said most of the time we're using or again with green year it's an organolithium interchangeably except for one reaction so same thing happens here with organolithium these guys are more powerful but in this instant it which is instance it would do the exact same thing and then of course we're going to add water in a second step and same thing as when you're using using lithium aluminum hydride you cooled the reaction vessel down in an ice bath and then you cautiously add a drop of water you wait for the exothermic reaction to go away and then you add more okay so it's really very very extremely strong base here all right so that's type 1 carbon needles Organa magnesium organolithium cuprates we're going to talk about a little bit later because they do different chemistry they're sort of their own category sodium is satelite we've talked about sodium acetylide reagents we know that they can open up Epoque sides they can also attack carbonyls so familiar reagent unfamiliar reaction but you probably predicted that this something like this would happen I'm not worrying about stereochemistry because we have a chiral reagents reacting with a carbo reagents so it's going to look like that okay and then we add water in a second step and notice something also when we use acetaldehyde we're adding on a two-carbon piece but it's different than the two-carbon piece we do with an epoxy ID so we've also added on two carbons so let me circle what we started with so this is one two this is also adds on a two-carbon piece what's the difference between this two carbons piece and the one we did with an epoxy they're not the same right anybody have an idea yeah excuse me no well we're started with this we're adding two carbons onto this depends on the perspective you're looking from the perspective of the acetaldehyde yes we're adding on three pieces but if we're starting with this and we're ever adding on two pieces right here so the only difference here between this is remember when we added on the two carbon piece with an epoxy it was ch2 ch2oh the O H was on the end here the O H is right where we were bonded directly to the carbon of our of our nucleophile so the only difference is the location of the O H sometimes you want to use an epoxy it depends on what you're doing afterwards 10:7 what you're trying to synthesize but this I want you to point out that this when you use acetaldehyde you're also adding on a two-carbon piece okay it's just the only difference is where the hydroxyl is so I'm just trying to point these things out to you because they're going to be relevant when you do since start doing synthesis all right let's look at a typical reaction with a type 2 carbonyl all right and I'm not going to show you the product as we're going to work through what the product is on another possible mechanism for midterm one era is going to come from the methyl carbon magnesium bond we attack the carbonyl carbon we kick electrons up on top oxygen so let's just kind of follow it along we know leaving groups that we can you know things that can be leaving groups in this reaction we know things that cannot be leaving groups in this reaction so here's our tetrahedral intermediate does it have a leaving group yes tetrahedral intermediate has leaving group if it has a leaving group it's gonna leave so electrons on oxygen are going to come down now we're going to kick off our leaving group and now we're gonna look at the product that we get and we're going to make a decision about that's something more is going to happen or not all right so our product is that is acetone so it's a ketone is a ketone more reactive or less reactive than an ester it's more reactive than an ester so that means the the greener is going to add again can't stop here why can't you stop there ketones are more reactive than esters all right so what that means is that that grandeur is going to add again all right arrow comes from the carbon magnesium bond now we're attacking a type on carbon Yale we know what's going to happen next we know that since it's a type 1 we are not going to have a leaving group
absolutely no possible leaving groups here all right so our tetrahedral intermediate it has no leaving group therefore it's going to stop here until we add a proton source and we're going to add water first so conceptually the same thing is happening here as what happening with lithium aluminum hydride we're doing the same thing we're adding more than once here and so we we have to certainly have to add h2o in a second step and then when we do that we get our alcohol so this is also a synthesis of alcohols so there's our product we figured it out ourselves here and so um the way that I want you to approach these problems is rather than just memorizing products I want you to go through this thought process and figure out what the product is yourself so it turns out that you must use two equivalents of grignard if you think you can trick it and only use one equivalent and get that product cleanly you're wrong what you will get is that product and unreacted starting material okay so if you only use one equivalent if you only use one equivalent you will get 50% conversion all right now I don't remember Whitley specifically what kind of sapling problem but there was there's a sapling problem with either this or lithium aluminum hydride and they asked for all the inorganic products and so you just got to remember that right here I just kicked off a methoxy group so I'm also going to get methanol as a product aren't I when I start with an ester so you want to keep that in mind so you're going to get this plus you're going to this this methoxy group that you made is going to get protonated now I don't normally worry about that side product but it could be something that you would have to worry about if you were actually doing the reaction so you're going to get that product and you're going to get methanol so two products questions on inability to stop at the ketone anybody having trouble with that I think one of the common misconceptions that I see in organic chemistry is people think well if I just use one equivalent and everything reacts simultaneously then it should be able to stop at what I want okay and it's not that way because these reactions are not happening simultaneously so in other words if I lined up all the esters in a row and then I lined up all the grignard right next to them okay in a long line and I said okay on your mark get set go then they all reacted simultaneously then I would be able to stop at the ketone but you you and I know that's impossible to do they're reacting a little bit at a time and as soon as you make a more reactive product it's going to react faster with the grineer that citria hasn't reacted yet okay so I know that's tricky but that's just the way it that's the way it works all right questions on that aspect anybody we like to think we're in charge of these molecules but we're really not they're going to do what they're going to do as any grad student will tell you all right okay let's turn this to an example with an acid chloride and organolithium reagents same idea here let's go through the mechanism so another possible mechanism for a midterm one we got a lot here do you remember to put lone pairs on all your reacting atoms when you're doing a mechanism so let's see what we get here so rather than just writing what the answer is I'm going to I like to go through it so we can you can think your way through to the answer all right tetrahedral intermediate has leaving group so electrons on oxygen come down and kick off that fantastic leaving group chlorides a fantastic leaving group alright so then let's look at the product and let's make some decisions here what's more reactive an acid chloride or a ketone as it quite so theoretically we should be able to stop here the problem is the same problem we had with lithium aluminum hydride there just - it's too reactive to stop there okay it's just way too reactive so it's going to add again unfortunately or maybe fortunately if you want that product okay so it's going to add again so and we'll label that very clearly should be able to stop here because an acid chloride is more electrophilic than a ketone by far the problem is is that grenades are too reactive all right so you can't stop here so
these powerful reagents are just too powerful to stop and so it's going to add again and so what do we get from that step when it adds again we can gosh we get the same thing that we get with an ester we get the same exact thing oops I skipped a step didn't I let's fix that so you get an alkoxide same alcohol you get with an ester tetrahedral intermediate it has no leaving group therefore it stops here and then when you add water we protonate and we get the same exact product all right so there's two examples of reaction with type two carbonyls yes yeah right how about that organolithium thank you for catching that they're so interchangeable I mean you're interchanging the names that I shouldn't do that okay more questions anybody all right so Greeners will also add twice to acid chlorides because they're too reactive cuprates which are the least reactive organometallic reagents will add only once so cuprates do their own chemistry think of them in their own special category okay this reaction only works with acid chlorides only works with acid chlorides no other carbonyls okay so so cuprates having copper now coppers a transition metal and so they do have their own different chemistry that's completely different then I'm grignard an organolithium compounds but they do they will react with acid chlorides to make ketones now I'm going to draw arrows for this this isn't really how this reaction takes place but this is a way you can think about it cuprates again they do their own chemistry and it involves radical reactions but I'm not going to show you that I'm just trying to give you a conceptual basis here but the idea here is that these are going to attack the carbonyl carbon and they remember these were the least reactive of the three so they will only react with acid chlorides and since they only react with acid chlorides when we form the ketone here it's not going to react again so we have the tetrahedral intermediate has leaving group so leaving groups gonna leave electrons come down kick off the leaving group and since cuprates don't attack any other carbon eels but acid chlorides we it stops here so if we want to stop at the ketone we have to use an acid chloride with a cuprate if we use an acid chloride with a granular again a lithium it will add twice give you the alcohol so that's that's the way to do this all right and let's just label this when you go back I won't ask for cooperate mechanisms this is not the true mechanism way too complicated the true mechanisms are not completely on 100% understood and way too complicated for this class okay yes that compound there with an aldehyde on one side in an acid chloride those are very unstable so I don't know if you can actually do the cooperate reaction do you know there's there they're very unstable they decompose into carbon monoxide and hydrochloric acid so I don't know whether I don't know the answer to that yeah yeah yes okay what about carboxylic acids will they work in this reaction well remember we will remember what we don't want to forget we're so tapped into the carbonyl we don't want to forget about these city hydrogen don't forget acidic hydrogen alright so the first thing that's going to happen these guys are extremely powerful bases we're going to deprotonate that acidic hydrogen all right and we know something about carboxylates we know that they're the least reactive of all the carbonyls so the question is are our carboxylate and you look at a carboxylate you normally think of an electrophile as having a partial positive charge or a full positive charge right this has a negative charge so we would it's it's kind of strange to think of it as an electrophile anyway but the question is is a greener to our site product is methane by the way that's our side product that's methane gas which is going to bubble off the reaction mixture and the question is is if we if we if we have an additional equivalent agreement queered is it strong enough to attack a carboxylate and the answer is no so methyl magnesium bromide is not powerful enough so it's powerful but we've come to the limit of its of its strength not powerful enough to attack a carboxylate okay so if it's not powerful enough to attack a carboxylate which is what is powerful enough to attack a carboxylate organolithium okay so this is the one reaction where they do have a different something happening organolithium is more powerful so if we want to have that happen again we'll talk about what happens next time
see if you could try to figure it out on your own
Loading...
Feedback
hidden