Hydride Reagents and Addition to Carbonyls

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Hydride Reagents and Addition to Carbonyls
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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: 01:59 - Reactivity of Various Type 1 and Type 2 Carbonyl Compounds 03:09 - Order of Resonance Stabilization 16:13 - Irreversible Addition Reactions of Type 1 and Type 2 Carbonyls 24:50 - Addition of Hydride Reagents
Sense District Ionenbindung Asymmetric induction Ester Activity (UML) Sunscreen Carboxylate Resonance (chemistry) Chloride Wursthülle Chlorine Chemistry Reactivity (chemistry) Electron Shear strength Derivative (chemistry) Atom Periodate Chemical element Area Setzen <Verfahrenstechnik> Acyl Stickstoffatom Induktiver Effekt Ketone Iodine Carbon (fiber) Carbonylverbindungen Aldehyde Food additive Heck-Reaktion Lone pair Combine harvester Acid Computer animation Acid anhydride Functional group Etomidate Chemical compound Bromine Cobaltoxide Base (chemistry) Carboxylierung
Asymmetric induction Induktiver Effekt Ketone Resonance (chemistry) Carbon (fiber) Carbonylverbindungen Aldehyde Wursthülle Methylgruppe Steric effects Combine harvester Hydrogen Computer animation Electron Functional group
Setzen <Verfahrenstechnik> Asymmetric induction Weakness Carboxylate Resonance (chemistry) Formaldehyde Chloride Carbonylverbindungen Wursthülle Food additive Reactivity (chemistry) Hydrogen Acid Computer animation Colourant Acetone Acetaldehyde
Chain (unit) Aluminium Chloride Methoxygruppe Chemistry Alkaloid Ethanol Dreifachbindung Molecule Alkalinity Electron Hyperpolarisierung Elimination reaction Metallorganische Verbindungen Sodium borohydride Aluminium hydride Dye Hydride Sodium hydride Concentrate Walking Alkoxide Addition reaction River source Chemical reaction Alcohol Butyl Food additive Electronic cigarette Wine tasting descriptors Reducing agent Lone pair Branch (computer science) Acid Blue cheese Chemical compound Cobaltoxide Thermoforming Methanol Stop codon Alkyne Ionenbindung Ester Species Reaction mechanism Activity (UML) Carboxylate Ice sheet Wursthülle Methylgruppe Reactivity (chemistry) Abzug <Chemisches Labor> Ring strain Solvent Lactitol Common land Tetraederstruktur Redox Explosion Lithium Conjugated system Atom Oxide Process (computing) Chemical reactor Palladium Setzen <Verfahrenstechnik> Dyeing Flame Ketone Hydrogen bond Carbon (fiber) Carbonylverbindungen Aldehyde Protonation Electronegativity Water Hydrate Sodium Hydrogen Ice Drop (liquid) Computer animation Functional group Proteinkinase A Covalent bond Boron Base (chemistry) Mixing (process engineering) Deuterium Quenching (fluorescence)
all right so we're talking last time about carbonyl chemistry carbonyl compounds are electrophilic we're going to be talking about a lot of different carbonyl compounds and so we want to have a good understanding of reactivity why is one carbonyl compound more reactive than the other we can memorize the order of reactivity but that's less satisfying than actually understanding the order of activity will enable us to make more complicated decisions when we get more deeply into carbonyl chemistry so relative reactivity is depend on
relative stability of each acyl derivatives so we're talking about a combination of inductive and resonance effects so we do have two factors here we have the inductive effect oh thing just a little touchy here okay so we have our group L we're talking about going to the compounds the carbonyl compounds to have Group L so type two carbonyl compounds as L becomes more electronegative it pulls electron density away from the carbonyl that makes the carbonyl carbon more positive and therefore more electrophilic but we also have an opposite effect which is the resonance effect and for the resonance effect it's its opposite because now the leaving group I mean that the group L is feeding electron density into the carbonyl carbon adding electron density so that's going to make the carbonyl carbon less positive less positive means electrophilicity less electrophilic so how are we going to decide which one's more important in which case okay so we're going to have to weigh the two in some cases the inductive effect is more important in other cases the resonance effect is more important all right so extent of resonance stabilization depends on how well the lone pair can donate its electrons we have a good measure for that base strength right the more basic and atom is the more it wants to donate electrons so remember our periodic trends for base strength and Oh F CL BR and I and we know that base strength increases in this direction and when L donates its a lot its lone pair it's actually donating a lone pairs which in a measure of how important that is for L is by measuring the base strength the more basic L is the more it's going to want to donate its electrons so as you can see nitrogen here is a stronger base than oxygen so when we have an amide that the resonance stabilization is going to be more important for an ammeter right because the nitrogen's more basic it wants to donate its electrons more so the second the resonance effect is going to be more important so here's the order of resonance stabilization here here's everything on the next page alright so most residents stabilized it's going to be a carboxy group followed by an amide followed by a ET so it's so an ester followed by a carboxylic acid followed by an anhydride followed by an acid chloride so the most resonance stabilized it's going to be a carboxy group and so let's do some residents draw some resident structures here for these guys and I'm going to pretty much hit the two extremes here so we can draw a resonance structure for a carboxy group so that's a deprotonated carboxylic acid we see that we have two equivalent energy resonance structures both have identical energy so you could it makes good sense here that this one is going to be the most resonance stabilized so we have two equivalent resonance structures so this one has the most resonance stabilization all right so then now let's look at the look at the amide we know that nitrogen is pretty basic it likes to donate a pair of electrons here so it's going to really want to kick in electrons and kick those electrons up on to oxygen so we can draw a second resonance structure here so two resonant structures for the a mid now which of those two resonance structures for the Emmet is the most important one the one on the top or the one on the bottom one on the bottom so this is so we have definitely with the second resonance structure where there's a negative charge on oxygen and a positive charge on nitrogen but now we have added separation of charge so that's not as good as having something with no separation of charge and so it makes sense that although the nitrogen does like to donate it's a pair of electrons is not going to be as resonance stabilized as a carboxy group okay and then so that we can keep doing that doing this all the way down let's go to the last one here that has the least resonance stabilization and let's draw the resonance structure for that all right so chloride ion a very strong base what do you think not a very strong base right so it's not going to want to donate its electrons so that would suggest that the acid chloride is not very resonance stabilized right and so it's the least resonance stabilized of all of these so we can look at basicity to explain that and we also can look at another factor that might not be obvious we know that chloride ions the weakest base but there's also something else in play here and that's that there is pour 2 P 3 P overlap okay what the heck is that so if we have a regular if we have an amide we have a PI bond between a carbon and a nitrogen those are both second row elements and so that would be 2 P 2 P overlap so unlike a carbon nitrogen bond would be 2 P 2 P overlap or carbon oxygen would be 2 P 2 P when we have a chlorine and an oxygen I mean the chlorine into carbon we have a mismatch in the size so here's two P and then we have 3 P this is much larger so here's our carbon and here's our chlorine over here this would be a carbon and our nitrogen here's our carbon that's our chlorine and if you actually look at the area that's overlapping it's not very much right here's where we get the overlap right in here and right in here and you can see that on the chlorine the most of the electron density is far away from that overlap part so there's not a there's not as good of overlap poor overlap is is equal to poorer resonance stabilization so what we can say here to summarize going this direction increasing base strength and then this direction increasing resonance stabilization so you can imagine if you place that chlorine with a bromine or an iodine that's going to be even worse okay that's going to be even worse overlap there all right so aldehydes and ketones are
in their own category because they don't have a group Alvah can stabilized by resonance so let's talk about them separately and then we'll summarize everything so a combination of inductive and steric effects are what we use because we don't have resonance effects here to talk about but if you remember from 51a that that methyl groups are slightly electron donating okay then so that means that again we're going to do the same thing we did previously where we're looking at partial positive charge on the carbonyl carbon and seeing which one has the most partial positive partial negative so we have one one methyl that's electron donating here we have two methyls that are electron donating two electron donating methyls so which carbon is going to be the most what's good which carbon is kind of at least partial positive charge okay this the with the ketone right because we've got two electron donating methyls with the aldehyde we only have one so for an inductive effect we can just simply go
let's let's summarize inductive effect methyl is Elektra is an electron donating group that's going to make carbon less positive over here we have two electron donating groups like which are methyls so therefore less positive charge on carbon therefore that's going to be more stable more stable equals less electrophilic so that's inductive effect the inductive effect would tell us that in aldehydes more reactive than then a ketone and that's absolutely true and now let's talk about steric effects which of which one an aldehyde or a ketone is less sterically hindered aldehydes less sterically hindered so hydrogen less sterically hindered than a methyl so in this case the inductive effect and the steric effect are telling us the same thing that aldehydes are significantly more electrophilic so aldehydes or more electrophilic than ketones questions so far anybody okay I don't know how well this
shows up what do you think compare electrostatic potential maps of the various type on carbonyls so this is formaldehyde we'll draw it right underneath in case you can't see it through the color there this is acetaldehyde and this is acetone now remember with electrostatic potential Maps the more blue the more electrophilic and so allegedly I don't know how well it shows up but the formaldehyde with two hydrogen's as it is definitely more blue than acetone does it look like that went that way to you or I'm just kind of making it up depending on how the picture is is drawn I think it looks more blue and it is it's more electrophilic so formaldehyde more electrophilic than acetaldehyde more electrophilic than acetone okay so you can clearly see that let's summarize all these together here's the order of
reactivity here and you absolutely need to know this you guaranteed will have a problem on midterm one where you're asked to rank these rank or pick me the most electrophilic least electrophilic okay so something like that on the midterm and you'll likely see something like that again on the final it's really important it's going to help us make decisions okay when we get to more complicated things alright so acid chloride most reactive because it has strong inductive and weak resonance inductive destabilizes resonance stabilizes who has strong inductive which destabilizes it and makes it more reactive in a weak resonance so we're not getting very much stabilization for resonance so definitely and so because of that acid chloride is the least stable most reactive so most most most electrophilic of all the carbonyl compounds and then we go to the bottom Here I am is right above carboxylate carboxylate has the best resonance remember there's 50% one resonance structure 50% the other so we have the best resonance and so carboxylate anion is going to be the most stable least reactive all right again absolutely have to know that that will be on the test guaranteed alright
so now we've talked a lot about reactivity now we're ready to work move into talking about reactions so in this chapter here we're going to focus on irreversible addition reactions of type 1 and type 2 so when powerful nucleophiles add to type 1 and type 2 reaction is irreversible so we have hydride reagents source of h- we'll talk about those first and then we have organometallic reagents source of our - and I'm gonna put these in quotes because we really don't have straight h- and straight R - but there are sources of those okay so I'm going to put those in quotes and then sodium alkyne IDEs those we talked about in Chapter 11 so this is a source of remember deprotonated terminal alkynes so these guys will also add two carbonyls we're familiar with that reagent but we haven't talked about their reaction with carbon yells but I bet most people would be able to predict what happens with that without me even telling you anything I'm thinking all right so let's
look at a type one example here nucleophile attacks the carbonyl just to remind you through the activity that's addition tetrahedral intermediate okay because these are powerful nucleophiles they're really strong the nucleophiles they're strong bases they can't come back off again that's what makes this irreversible tetrahedral intermediate has a no leaving group and so it is an therefore an irreversible addition so since we don't have a leaving group what we're going to end up was I'm going to stop there and we're going to add water in a second step at h2o or h3o plus in a second step so what we're going to end up synthesizing I'm using the type 1 carbonyl compounds is is alcohols and so our nucleophiles are here h- I'll put that in quotes because it's not really straight H - R - these guys are all things that can't be leaving groups and certainly sodium alkaloids what's the pKa of the conjugate acid of the sodium alkaline remember what that was that was one of the ones rounded to the nearest five 25 so it's not going to leave right that's what so that's what these all have in common that's a typical reaction with a type 1 and then we're gonna typical reaction with a type 2 on the next page nucleophile attacks tax the carbon eel Carville we kick electrons up onto oxygen we get a tetrahedral intermediate we look at that tetrahedral intermediate now we decide does it have a leaving group yeah it does it has a leaving group l so tetrahedral intermediate has leaving group if it has a leaving group that leaving group is going to leave so electrons on oxygen are going to come down and we're going to kick off our leaving group all right ASA substitution right if that nucleophile is one of these three nucleophiles we have indicated here what would that what's that compound what is the structure of that would it what would category would that be it's gonna be an aldehyde or a ketone right it's gonna be if if it's if it's if the nucleophile is hydrogen right here on the previous page that'll be an aldehyde if it's R it'll be a ketone if it's sodium alkyne I'd then it's going to be a ketone that's conjugated with a triple bond right so because this is an aldehyde or a ketone the reactions going to happen again because we just did it right here right when we add these nucleophiles here we get that so that's what's going to happen so we have an aldehyde or ketone here as our product and so the nucleophile is going to add again just like you did on the previous page one more time we get a second tetrahedral intermediate do we have a leaving group no nothing can leave has no leaving group okay so it's going to it's going to be just like this tetrahedral intermediate it has no leaving group so that means that we're going to add water or h3o plus we'll just say h2o in a second step and that's our product so we're also making an alcohol except this time we have two nucleophiles Incorporated that's the general thing that's going to happen for the rest of this chapter there's some there's some differences and there's some special reagents that we can use where it will stop right here at the aldehyde or a ketone but most of the time you can most of the time you can't stop questions so far yes it's the second reaction will you tell me we just talked about reactivity right so let's go back let's let's go back and look that's a great question so let's see and this is why you need to know this right okay so we have acid chloride and hydride all died so then ketone so if it's an ester carboxylic acid or a mid will we make an aldehyde or ketone that's more reactive than the starting material and that's one of the reasons why you can't stop okay so excellent question yeah so once you make the aldehyde or the ketone it's actually more reactive here you know it depends on what you're starting with whether you can stop or not okay so and we will get to that more questions anybody yeah no you can't and we'll get to that there's some special reagents that you can use to stop but I understand that they don't work very well so we'll talk about it when we get to them and there's ways around that so what I want to do right now is I want to talk about hydride reagents first and then I'm going to talk about the other kinds we go again in metallic compounds so nucleophilic dition of hydride to the electrophilic carbon results in reduction of the carbonyl group okay so what's happening here boom I have it in quotes because hydride by itself doesn't work in this reaction so can you do this reaction with sodium hydride no can't do this reaction sodium hydride does not add to carbonyls so we have special reagents that do then you do the addition and then you add water or acid in the second step and as you can see we've actually reduced the carbon oxygen double bond so the rages that we will use sodium borohydride nabh4 lithium aluminum hydride you're also familiar with that no sodium hydride so so sodium hydride only acts as a base not a nucleophile so seems like it should work but it doesn't work so the regions that we're gonna see sodium borohydride Lucia monohydrate and some other special ones that we will encounter as we as we go along in this chapter all right so these two hydride sources behave very differently and maybe if we draw the structures we can figure out why that is so sodium borohydride has a boron hydrogen bond lithium aluminum hydride has a aluminum hydrogen bond and one of the ways that we can predict the reactivity the relative reactivities of these two compounds is to look at electronegativities and so we see let's see we have for boron 2.0 hydrogen 2.2 aluminum 1.6 hydrogen 2.2 alright so for both of those bonds we have a polarization we have partial positive charge on boron partial negative charge on hydrogen so electron rich hydrogen notice this is the opposite that we see with an acid with an acid we have partial positive hydrogen so we have partial positive on aluminum partial negative on the hydrogen which one of those bonds is the most polarized yeah lithium aluminum hydride and so blue theum aluminum hydride there's the most partial negative charge on hydrogen so it's a more reactive form so sodium borohydride is much weaker than a lithium moven hydrate reacts slowly with water and this reagent only reacts with aldehydes and ketones lithium aluminum hydride as you can see from the polarization of that bond it really acts much it's a much stronger reagent reacts violently with water you used to hit you have to use dry solvents you have to use dry glassware so you pre bake your glassware or you flame dry it you use dry solvents and you quench very carefully the quench is a addition of water after the reaction is done so that's what we mean by quench addition of water after reaction is done I had an explosion with lithium aluminum hydride when I was in grad school we one of the things that lithium aluminum hydride is used for is drying solvents so if you add a solvent to lithium aluminum hydride you will suck up all the water and then you distill your solvent over and I was distilling a solvent in grad school over lithium aluminum hydride and I walked in I had it going in my hood and I lowered the lab jack to stop it because it looked like it was done and I saw that I still had a little bit of solvent left in the bottom I wanted to go a little further so I rolled back up the lab jack so it was still heating and I closed the sash and I went to two steps and the whole thing exploded so I like to had in my I would have had my hand in there like seconds earlier so it's very it's very violent reaction so one of the things that I'm a stickler for is if you're using lithium / hydride don't combine it with water if you don't number those steps you're gonna you're gonna miss the points okay because it reacts violently with water so if you added water to so when you do a lit the over a reaction with lithium aluminum hydride you cool it down and you put it in an ice bath and then you add a one drop of water and you'll see Shh you know do you hydrogen gas coming off and then you'd like that cool and then you add another drop so I'm so what I'm saying don't mix lithium aluminum hydride in water together okay sodium borohydride on the other hand reacts slowly with water so it's a much milder reagent but it's also not as powerful so the lithium aluminum hydride reacts violently and it's going to react with all type 1 and type 2 carbonyls reacts with all type 1 and type 2 carbonyls so kind of cool biet to be able to predict that reactivity just by knowing some electronegativities and it exactly what you would expect it to do i do want to label this so when you come back and see that later you'll know what we're talking about here so here greater concentration of negative charge on hydrogen therefore it's going to be more reactive and what we're going to see is when we start talking about there again I metallic reagents as we can make the same predictions that we did here just based on electronegativities all right so here's a typical reaction with type 1 carbonyls so good news you're familiar with lithium aluminum hydride from 51b that's one less reagent you have to memorize so hopefully it's already in your head and what we did with the lithium aluminum hydride in 51b is we had it attack it with hoc sides right that was something that we did in 51v alright so the arrow comes from one of the four aluminum hydrogen bonds to take your pick it's going to check the carbonyl we're going to kick electrons up onto oxygen so addition of hydride to sp2 carbon now it's a little easier to see now that we're using real reagents rather than just an you generic do we have any leaving groups on this tetrahedral intermediate hydride can't leave pKa of the conjugate acid is 35 methyl can't leave pKa of the conjugate acid is 50 okay so those are not those are not going to leave so our tetrahedral intermediate has no leaving group so as much as possible I want to encourage you rather than memorizing products to actually go through the process of seeing what the reagent does and being able to make decisions and then and then if I give you something that you haven't seen before you'll be able to get the answer easily okay so a tetrahedral intermediate we say that of course because it's sp3 now has no leaving group and it's also and it's so therefore it's an irreversible addition all right so that means it's going to stop here until you add what water water or acid in a second step okay and so then once you add water if I ask you the mechanism for this on midterm one you would just simply show the protonation of the oxygen so that's going all the way back to chapter two all right result is reduction of the carbonyl how do we know it's a reduction we actually we lose this lieu of the loss of carbon oxygen gain of carbon hydrogen so we talked about how to figure out whether you have an oxidation or reduction that was back in chapter 12 so if you don't remember that you can take a look okay so therefore a reduction alright similar reaction occurs with type 1 carbonyls in sodium borohydride virtually the same reaction this thing is much more touchy than the one in the other room I'm gonna have to get used to that so sodium borohydride right arrow comes from one of the boron hydrogen bonds we attack the carbonyl carbon we kick electrons up onto oxygen notice with sodium borohydride we're going to actually protonate with ethanol they don't have to be in separate steps they can be mixed together okay so it's it's you don't have to number it with sodium borohydride again tetrahedral intermediate has no good leaving group and that's because the hydrogen that we just added can't come back off again so this is the hydrogen that we just added this can't come back off because it's a terrible leaving group so can't leave therefore irreversible all right and then in the second in the second reaction here here we don't have it as a second step it is actually in the same reaction vessel and I'm just like I said this thing is a little bit different I'm gonna have to get used to it h OE T right so we actually protonate with ethanol which is the solvent that you use for this reaction questions anybody so how do we do this real hard we reduce aldehydes and ketones back in Chapter 12 do you remember how we did that hydrogen and palladium that's not the most common way to reduce aldehydes and ketones these are the more common ways so that's not very common to do that in Chapter like we did in Chapter 12 this is the more common way to reduce a carbonyl all right so that's what happens with type 1 let's do type 2 do we need to talk about sodium borohydride with type 2 no because it only works on aldehydes and ketones so we're done with sodium borohydride all right so the theme liu and hydra we can do this right we're going to go through here one step at a time rather than just predicting products memorizing products having the whole sheet that you memorize we're going to go through the thought process with the aluminum hydride very powerful nucleophile arrow comes from the aluminum hydrogen bond we attack the carbonyl carbon we kick electrons up onto oxygen addition all right so let's let's analyze our potential leaving group certainly methyl can't leave hydrogen can't leave what about methoxy okay yeah it actually can in this reaction we'll talk about why that's allowed here that wasn't a leading group in an sn2 right but we can actually have it leave here so what I told you is in Chapter seven if you had my class I said methoxy can't ever be a leaving group in an sn2 reaction can't ever be a leaving group but we're going to have exceptions of course this is not an sn2 reaction we're going to have exceptions and I'm going to bring them up as they come along so this is exception number one so we know that methyl certainly can't leave lets oxy what's the pKa of the conjugate acid of methoxy what's the pKa of methanol rounded to the nearest five is fifteen right shouldn't be a leaving group but it's okay in this case so this can leave all right so what we're going to have is elimination here so notice what I'm doing in my arrow pushing I put lone pairs on all the reacting species if the oxygens reacting I have it all of its lone pairs if if the methoxy group is leaving I have all of its lone pairs alright so let's see what we get after that step addition elimination and that's what we'd expect for type two alright what do we know about every activity of an aldehyde versus an ester what's more reactive an aldehyde or an ester aldehydes more reactive okay so aldehydes more reactive so we can't stop here can we so this is more reactive than an ester therefore we can't stop here so what's going to happen is the lithium aluminum hydride is going to add again let me draw it up here where I have a little more room it's gonna add one more time now we're going to get addition only why because that's a type on carbonyl it doesn't have a leaving group but in case we didn't notice that already let's just draw the product to the tetrahedral intermediate that we'd get and see if we have any leaving groups we certainly do not have any leaving groups hydride to hydrides and a methyl can't be a leaving group so tetrahedral intermediate has no leaving group there are four stops here until you add water in a second step so step two h2o then we protonate our alcohol we protonate our alkoxide to get an alcohol questions on that mechanism anybody possible mechanism for midterm one alright so you're very upset I can see that by the fact that we have alkoxide has a leaving group let's explain why we're allowed to do this in this case here we couldn't do it in an sn2 but we can do it here let's compare an sn2 reaction so this again was chapter seven chapter seven nucleophile we said this can't happen so this doesn't work so we'll draw it then we'll put a big extra so that would be backside attack having alkoxy as a leaving group and what you'll notice is that the product and the reactant a similar energy product and reactant have similar energies so we're not doing anything to dramatically change the stability of this atom by doing that sn2 reaction we are on the other hand in this reaction here we are dramatically changing the reactivity because if we have these electrons come down and kick off from a top C group we're getting an aldehyde aldehydes much more stable the carbon oxygen double bond a very powerful double bond and so in this case the aldehyde is much more stable than the tetrahedral intermediate we also had an alkoxide as a leaving group one more time already Chapter nine right what reaction was that where we had an alkoxide as a leaving group you better remember so I apologize this was our second exception we had a first exception in Chapter 9 how about opening up an epoxy why not notice that Wow when we do this reaction we are actually having an alkoxide as a leaving group it happens to be in the same molecule it's attached to the molecule but we do have an alkoxide as a leaving group and we talked about the fact that this was allowed and why it was allowed last quarter but make no mistake about it and this is an sn2 reaction so as you can see we sometimes break these rules that we have in chemistry when we have something going to something much more stable than what we started with and so again product is much more stable than reactant because we've relieved that ring strain questions anybody all right important points about hydrate addition to carbonyls remember sodium for Hydra is not powerful enough to add to type 2 carbonyls so just aldehydes and ketones for that one lithium aluminum hydride adds twice to esters even if only one equivalent is used to stop at one addition use an IO reagent called isobutyl aluminum hydride or die ball here's our abbreviation right here and you can you feel free to use the abbreviation it's stronger than sodium borohydride be less reactive than lithium hydrates is use exclusively to reduce esters to aldehydes and it doesn't work very well right it just really works loud every neta i've never done the reaction but neta I've ever had said that's a really lousy reaction it doesn't work very well so I'm gonna give you an alternative that you might like better if you don't want to memorized eyeball let me show you what this looks like so dye isobutyl remember what iso means we have a branch on the end of the chain dye isobutyl aluminum hydride different than lithium aluminum hydride because we don't have four groups around aluminum do we what would we call that when that aluminum only has six electrons well what would we call that - two names we would possibly call that maybe back and maybe even from back in G chem there now we're really going back it's as we call open shell or a Lewis acid right so and we have an oxygen here that has lone pairs so the lone pairs on oxygen are going to want to attack that that's the first step but we'll stop right there and you guys are just going to have to wait till we come back on Monday I hope you have a great weekend