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Lecture 12. The Aldol Reaction and the Michael Reaction.


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where want alright well we now start Chapter 24 hour and we really come to what I think is the pinnacle
organic chemistry in terms of reactivity mechanisms the system retro synthetic analysis and this is the carbon meal chemistry of various types of Carbondale condensation reactions the Algol reaction the Michael addition the Clayson condensation the the Robinson annual Asian reaction the intramolecular called the Diekmann cycle is Asian the intramolecular reaction it's putting together the reactivity of carbon meals that we learned about his electrify Olson the reactivity on the alpha carbon is nucleophile and
being able to assemble some very complex and important and beautiful molecules as a result of this is also a lot to think about it and so what I'd like to do is to start talking about the Algol reaction which really lays the groundwork for all of these Carbondale reactions and
indeed even some of the sugary chemistry of the learning about later on in the in chapter as the 20 year feature 26 against far-right sold in Indiana all reaction in general what happens is an e-mail late reacts with another carbon yield compound so you have a carbonyl compounds and I'm going to write this varies very generically a carbonyl compounds with an alpha hydrogen in honestly we're talking about just about any of them .period 62 owner Al behind families but also the Astor
family honestly even know I've written this says carbon meal exercise said in this broad Esther family in this broad carboxyl against
acid family you have carboxyl like acids but also nite trails and so the chemistry all talk about today even as applicable in certain cases the knife at
nite trails but the main thing is we have a carbonyl compounds where now hydrogen and we have some sort of basis will be talking a lot about basis right now and just giving this sort of as a generic generic characters and under some conditions we
get life and we allow that carbon compound to react with the Keatonâ held up high sometimes all mixed together sometimes government sequences will talk more about specifics in a moment and the
Hanalei draw my negative charge here the INA late of course is nucleophilic at the Alpha position between tone around the Hyatt is Electra fell like in so we form a bond between the Eagle Lake and the Keatonâ elder hide in the most
generic form the initially formed product is going to be and the late but and under some conditions sometimes as part of the reaction conditions sometimes in a sequential separate stamped of a proton sources can become available or to Wheaton add a proton
sources I'm writing this very generically as H plots could be added acid it could even be alcohol or water in the reaction mixture will go through details in a moment but whatever your protons sources here again very generic songwriter from Tom source would area protons source says we have made the
Oxy and iron of the Al delayed and the overall result is an old old product but in you can recognize and Algol product because it's a beta hydroxy carbonyl compounds later on also show you out algal Algol
products that are alpha-beta unsaturated carbon you'll come so that's sort of the overview it's at 5 thousand feet I now want to go to a very specific example I'd love the Algol reaction I love it intellectually because there's so much to think about mechanistic police synthetic I also love it because it's beautiful to to do more synthetic lay in the laboratory and solid give you an example that I use in my Kim 160 laboratory Class I wanted a simple sort of cookbook
Algol recipe for my students it's the 1st day of laboratory this is an upper division laboratory course I urge you to take it it's a lot of fun and the 1st day all in 1 day they do annulled all reaction and purify the product by 1 of my favorite recipes which is basically you take some LDA in ths we talked before about how often you will make your own LDA by reacting Bureau lithium of very very strong base with dies probable means somewhat less basic but still very strong and satirically hindered based organic chemists often cool things with dry ice dry ice is negative 78 degrees Celsius which is why you'll often see that otherwise odd sounding temperature that intercept that who
1 and the carbonyl compounds you generate being elated negative 78 degrees the Carbondale compound that I chose for my team 160 students who has been so old pH is just a benzene ring a C 6 H 5 unit Denzel known as just a simple carbonyl compounds and then the source of a glorious acid that I like to use is a Rios ammonium chloride just a mild acid right NH 4 classes acidic all right this in parenthesis as aged real class you could write either underneath the error but this is sort of my favorite cookbooks what's called the directed Algol reaction directed meaning were 1st generating the life were then in a separate step adding a carbon compound and isolating the product sold right and fallible reaction capitalized Algol here is a title but goal is a word it's not a proper nouns so if you just riding it you wouldn't capitalizes Michael which will hear about in at the end of today's lecture is actually somebody's name alright so the Algol product that you get in a specific
example that my students and 10 160 get in read crystallized a beautiful beautiful white crystals great yielded just the fun laboratory experiments to do and it
is this beta hydroxy Esther all right I want to give you another example this particular recipe for directed Algol really just works and works and works of gave him another
example just so we can see some of the diversity here regeneration in the light of an ester we reacted with the key town of just for variation and say Let's take cyclone had known the LDA I know you
stress over what to write and examines here I'm not writing the temperature by doesn't matter whether I do or don't I'm writing ths probably doesn't matter whether I do or don't don't stress too much but very important we're going
ahead 1st number 1 generating media light show and this time I think I'm going to use an Gore highlighted in this generic in this specific example let's use ISO Bureau out the high-desert carbonyl compounds 3 methyl to Mathilde program now and will do in a it's worked out and
here be a little more generic and just right page 3 last also located do H 3 Alpha Plus could be made with ammonium chloride it could be date we estate would and sulfuric acid and in a very
very difficult situation you would then extract your product into an organic solvent and rioted over and sulfate in the filtering and constantly and here's are out all products another beta hydroxy Carbondale compound in this case are light was generated from a McGee told in the previous case from an Ernesta in this
case are like profile was now the behind the previous case Quito alright what I want us to do at this point is to learn to recognize the Algol synthesis and so I want us to get in the habit of warning to think backwards we've talked about retro synthetic analysis before it's a very important skill To be able to see backwards since all right out a simple problems showing the type of thought process
so this is exactly the sort of thing that students in organic chemistry and research encounter all the time they're making
a complex molecules like a natural product and they need to make it from stuff you can buy and so I'm going to the phrase that's as synthesizer now
drop compound here rather than meaning that but you can you can figure figure is the name of it if you like the what I've chosen for this particular example in this molecule and I'm going to assess size
this molecule From simpler compounds the
worldwide because generally as you build up bigger molecules with more functional groups there's more complexity chances are they're not
available but simple stuff is available you can buy on the exam I gave you a sort of restricted chemical catalog of 4 carbon atoms a few that sort of an artificial example but it's basically what people deal with there's a bunch of stuff you can buy out the heights tones Al kinds alkyl halide alcohols AL teams allocating go-ahead use anything
you like to make this now let's focus on the thought process and remember that they thought process that we use this real height of thinking Nobel Prize-winning thinking J Corey type of thinking is the idea of thinking
back words retro synthetic analysis and use this type of open-air of this show
represents that analysis the beauty of being able to think backwards as it liberates us from conditions from reagents from details what oxidizing agent do I use what they still
I used to see the entire big picture and the big picture here is we have a beta hydroxy Carbondale ,comma right this is the alpha carbon This is the beta of his data
hydroxy carbon and when we say a beta hydroxy carbonyl compounds
immediately that should coalesce sent the bond between the alpha and beta carbon can be made by now all reaction and so
I look at this maybe I draw little squiggly lines here to remind myself and then I look and I said Well wait a 2nd we've got this team tones on the laughter 3 Mathilde
to Buick known and we
remember on the right here that this alcohol was part of carbon compound before reform the bond and added nucleophile another words that came
from a tool acetone and so that's
the rector's synthetic analysis that's the act of thinking our way through the problem now we just go on and say Ah I aware we need and that we need to generate the inner life of 3 out 3 of the 3 Mathilde to view known and then we need to allow it to react with acetone to directed out reaction now we can worry about details rethink
that Wait a 2nd Wait a 2nd Wait a 2nd is this going work there to lights that can be generated with base
falls off an alpha proton we can pull off any related
Proton at the 3 position we can pull off a proton at the 1 position and we think back to read geochemistry and Connecticut lights and say that we're in good shape here
remember that when we treat a compound where you've got a less satirically hindered position like the methyl group and a more satirically hindered position like a nice of probable group the LDA this Baltic based
preferentially pulls off the more accessible Proton to give you the kinetic penalize to give you the late on this side we then Anna acetone and we carried out in a curious work out in
practice typically you might add the acetone and negative 78 degrees and allow the reaction mixture to warm up to 0
degrees before quenching it With some mildly we assassins like ammonium chloride
were seated guests at work I would HCL
and if you use something like a CDL you're not going to let the reaction get hot you're not going to store it within a
long time you just can't handle Daewoo HCL and immediately do you liquid with liquid extraction will come back to why that's important in a moment and later on our I like this by teaching about the Algol all this way and
I like to do the Algol reaction by the directed Algol procedure because it is
so intuitive it's this mind-set of taking control it's the idea of going to make the nucleophile I want I'm getting ahead the electoral file I want and .period that nuclear
file is gonna react without electrify all the way that I will now historically that's not the way the Algol reaction was developed and up
until just before 90 the 1970 LDA really wasn't on the scene as a base and a lot of organic chemistry was and continues to be done by mixing together some moderately strong base LDA is a very strong base and some carbon yellow compound or carbon compounds now the original out all the action was actually discovered at the beginning of the 19th century and I'll show you show you that reaction chemistry the
beautiful thing about about chemistry is of course that works across all time wall space and all places works on Mars works in the 15th century
it'll work in the 20 5th centuries so the original Algol
was acetaldehyde lines where the base and new text also makes reference to this
undeniably alone I about the base on the blackboard underwrite hydroxide now the Betsy graded according to my recollection I I read about this soul while back so I maybe frisee I think the base that was used originally with calcium hydroxide organic chemist for the most part don't use a lot of calcium salts ER calcium metal and synthesis these days sodium hydroxide a lot more common base so you textbook and probably I am not going to ride out CAL
age 2 because you're probably never going to see it again but the principle is the same reaction happened to be done in water as out the height is a small
molecule Water dissolves some small organic molecules writes that 1 oxygen atom for 2 carbon atoms and it was done it cold temperatures 5 degrees Celsius for 4 to 5 hours and the product that this reaction in about 50 per cent yield was the algal product of bringing together 2
molecules of acetaldehyde hybrid while this compound is called out all
trivial matters now you think about it you think about it I've already said a lot of the FO compound sought a bear the name of things when you go and you get a glass of scotch it contains alcohol that's ethyl alcohol ethanol when you go ahead and you get a bottle of that's Ethyl ether so it kind of makes and we talk about a was seated Esther right it's the ethyl ester and so it kind of makes sense that the archetypal Algol is the outer wall of acid out behind the 2 carbon unit and the product is called out as I said not a proper name doesn't get capital alright so what's going on in this chemistry what you should now be on top of things enough to ride out all of these mechanisms but I'm going to go through it again just
in case you're a little bit rusty alright so in this 1st step and this unlike the directed Algol it is a bigger Mitch is just as set out the high base sat together in a bottle of water for 4 to 5 hours and then worked out as the 1st
step hydroxide Anaheim the alpha proton 1 of the 3 Alpha protons all off just as we've seen before to generate an e-mail late last all of
these steps are equilibria songwriter equilibrium enrolled in the directed Algol we're taking a little more charge and basically because things are occurring at very low temperature and were using a very strong base their irreversible but here for the most part or all of our steps are equilibrium so we generate power being laid here are leaving the good person right in the
water our 2nd step in
this big mensch now we have plenty of Al behind just floating around out there hiding hydroxide in new way In light is nucleophilic at the Alpha position electrons flow from the EU laid down from the oxygen to the out
of position attacking the Alpha carbon remember we have to residents structures for the inner life I generally prefer to draw the more or the major resonant structure but in the back of your mind is also this resonance structure with negative charge on the output carbon and so this flow of electrons just embodying bringing that charges the negative part it's not add to the carbon it's not at 1 position or the other it's a bold positions at the same time but I can only 1 resident structure at a time electrons flow onto the carbon kneeled in this gives rise to the elderly you know in the last step of the reactions were in water in water during alcohol and truculence scandal and prone still we have lots and lots of water present so we had dismissed
action driving the reaction we picked up a pro-Taliban we regenerate our hydroxide but for
minutes you can see hydroxide is a catalyst for this reaction it's consumed in the 1st step but recreated in the last step and so it's catalyzing the reaction bringing together the 2 components it's 1 of the things that's confusing and learning the algal reaction is also the exact cost of the
reaction ends up affecting the products the products formed depending on the exact cost of reaction particularly in the non directed outdoor reaction we were just mixing things together typically we have a series of equilibration
securing and has the chemistry goes we can drive things further and further down downhill thermodynamic :colon so 1 of the features of the at the Al Gore reaction is that higher
temperatures In longer times to Intel leads to dehydration but To and by dehydration and
I in the loss Of the beta hydroxy group and an alpha hydrogen let me show you what I mean so let's take this howled all reaction and will
take SNL the high behind in base as they said these days people tend to use sodium hydroxide for the elder all reaction if you're running it under equilibrating
conditions it tends to be run water orange alcohols like ethanol and so all
save water and let us say he's in other words now instead of cooking that thing out are letting the single for for 4 or 5 hours at 5 degrees Celsius remembered chemistry is very slow and cold temperatures in general in general reactions go about 2 or 3 times faster for every 10 degrees
Celsius you go up from 5 degrees up to 50 or 100 degrees and reactions that might not otherwise occur can occur very quickly the the
product this reaction now please 3 beauty it is such to beauty now all right so what's occurring here everything that's occurred before is occurring but now we're getting another reaction In addition occurring as a result of the higher temperature on longer reaction times and this is what we call in the year 1 B mechanism it stands for elimination inserted base but
let me just show you what I'm talking about here and in this mechanism some of the issues part of the here's our hydroxide here's the beta hydroxy
current annual compound and so under these reaction conditions you can begin to pull off an alpha proton to get new no later than at 4 4 in their In a 2nd step we can spit out hydroxide but but but but the Sorrentino late kicks that we push our hydroxide which show but how how should the so
lot easier to think about if you remember the resonance structure in which we have a negative charge on the alpha carbon in that residents structure you can just think of it as directly eliminating as I said I prefer to write my you know like this way but you can think of it you can think of it just as well like that
Our great questions don't we need to make alcoholic and leaving so we seem to influence the imams in organic reactivity 1 is the theme of leaving groups in Essen to displace it hasn't toured displacement reaction of black leaving group passed there be a very very weak base its conjugate acid has to be strongly acidic chloride bromide iodide all our good
leaving groups HCL age 3 are a giant all had PKA is in the negative in general evanescent displacement reaction believing group is generally going to be a very strong acid for the conjugate base I brought cut off right at about positive for the PKK as I can give you examples where you have acetate as a leading group and that's about it as essential reaction you're going through this friggin abides pyramidal transition state carbon cannot have 10 electrons around it and that nucleophile is coming in the leading group is leaving right at the same time the bad reaction it's
a difficult reaction it only occurs with the good leaving the venue of the other classes of reactions with leaving groups announced their reactions we saw on carbon yield compounds with say Astor hydrolysis where now now we can have a leaving group that has of PKA of let's say 16
or 17 nucleophile adds to a carbon Neil we get attacked intermediate and that Tetra brawl intermediate takes out at dockside math oxide hydroxide in this type of chemistry the addition of elimination chemistry manifold allows much more basic leaving groups marched west good leaving groups weaving groups with weaker conjugate acids to leave and thus falls into that exact same manifold because you
won't get right hydroxide they're leaving group here PKK of the conjugate acid 15 . 7 but it's not going through that manifold where you have the fit 10 electrons only transient way around the carbon you cannot get a stable species
with 10 electrons but you can get a stable species with a negative charges Jason Adam everyone's happy it has 8 electrons you push everyone still has 8 electrons same ideas the breakdown of the territory
he will intermediate Wednesday in ethyl ester right in you here and we can push out after outside-half only really really important principle and I'm
glad you asked other questions at this point great question great principles I think the world we hope we will this couldn't be out sheen group formed where only the whole that's what we
call could we write the mechanism this was absolutely and this and this are just 2 pictures of the same thing of all member in your mind's eye you have
both resonant structures current let me give another example so I was playing with a SNL behind in that example and all sorts of other elder hides works
or just take a take a specific example this may have been from your tax but it just shows you the sort of conditions in the US
and behind example and in the end because of some reactivity isn't the best example is
far and principles of reaction but I want to give you a very specific example let's take puerile the high sodium hydroxide and 80 to 100 degrees Celsius and this is a real example from the laboratory you would never be expected to know the exact temperature the exact time but this a good reaction happens to run over 3 hours and I want us to look at the product for a 2nd because we're going to have to learn how to visualize these sorts of product and so
here is the product of reaction if you want a name it it's 3 Ethyl to now virtue and told you have seen a lot of the but the trade the
trick in recognizing these types of compounds is to be able to say got in my mind's eye I see that this double bond of its Alpha Beta unsaturated yield compounds
must've come from
outdoor reaction and when you look at that you say Oh OK I can see this half had been 1 molecule of abuse now and this half-year 1 2 3 4 had been the other half of you let's try another example phrase this is a problem just as I phrase the previous 1 let's say
cannot draw this compelling name let's
synthesizer I think this 1 actually may be may be an example from the textbook but it's a nice nice
example so I figured I'd use it let's say synthesized this molecule and again we're going to say this broader of from 1 simpler
compounds take a
moment for yourself to go through the Raptors synthetic analysis and let the molecule apart just like we envisioned here splitting this molecule and working backwards with the writers synthetic
arrow 2 2 molecules on Putin now what's the Carbondale
compound that generates this we know that so
the earlier period saying it the war and the factual name for this year's crop I often known so we're going to do the same thing where again if you want
the formal name it's 1 fennel program known so well splintered apart are Chloe is is that it's an alpha beta unsaturated carbon meal but at the end of the most
fled apart into 2 we around and recognize that it comes from 2
molecules of profiles for unknown and that's not the answer yes that's the thought process that's the showing our work that's the thinking on this so now we've learned about 1 instead of conditions for the Algol reaction with dehydration and so basically will just take up a pile for known and her favorite sodium hydroxide honestly you could use calcium you could use a pardon me potassium hydroxide interchangeable a water is a solvent a water
alcohol mixtures and he insists art of thinking back words that is just sold incredibly valuable and so incredibly powerful to be able to look at a complex molecules like that and see how it comes together so
women having some fun with chemistry that basically works works works well and what often means working for organic chemist is giving 1 thing it's this notion of control here I want the beta hydroxy carbonyl compounds or I want the alpha-beta unsaturated carbon you'll compound that but I don't want either I want this component to be the nucleophile or I want that component
to the media nucleophile but I don't want bold because of get a mixture can of course has 1 starts that have mixtures of things you have problems so for example if I mixed prop Ali and the international together with sodium hydroxide and water my goodness well
I could have the proper now be the nuclear file I and have the beauty and I'll be the nucleophile I could have the proper now be the electrified alike and have viewed now being the electrified out even if under these conditions I I didn't get any bigger hydroxy Carbondale and all of my beta hydroxy carbonyl compounds to to alpha-beta unsaturated Carbondale I have 4 4 different alpha-beta unsaturated carbonyl compounds I'd have
compounds with proper now and proper now compounds with proper Alan Budi now compounds with Putin now and proper now compounds with Putin met with proper now reviewed now and you now so in many circumstances
if you just mixed together different Al the hides and base you get a mixture of products but there is 1 special type of case where you can control mixtures of compounds and then generalities are if you
have a key tone in lies a bogey tone
obviously it's gotta be analyzable just like piled ethanol and you have a non-Indian analyzable
Al-Jihad like Kenzo old see the thing that special about how the hides
is there more Elektra fell Keaton's so there is only 1 species in that mixture that can generate Minot light because bends alcohol I can't generate nearly a dozen have alpha proton protons had all the tools electoral files a key told handed al the hide and held height is the better electrified so if we take these 2 components under the same conditions so you might peroxide in water and he even land they said you could have potassium hydroxide you could have a little ethanol and that mixture together and get things to dissolve but the main point is under these type of conditions there how we get a product and that product has the acetone acting as the nuclear file and the bends hide acting as the electrified out in other words even those we haven't had that precision we
talked about initially with the directed Algol with LDA which you could also do for a reaction like this .period and all make that he later of of acetone with LDA then all added into bends out the and all do the elimination separately under a under some other conditions but even without that we were able to take charge and we have a special name for this reaction we call this reaction crosstown Dole reaction by crossed I just
mean that we have 2 different components 1 of them said a key told that symbolize ball 1 of them is a nominee will Isobel all the hype and honestly there is some variation that 1 can have for example you don't have to have achieved on anything that you can make an evil laid off reasonably well is OK In general g tolerances are good in general remember the PTA said if you want to numbers in your mind keep to PKK is in your head 24 a and 25 foreign Astor and you can go ahead and say how the height is just about the same as a tone Sony analyzable out all the hype if you only want keep 2 numbers in your head you can say close
enough it's 20 OK so as how the hides more like 17 but that's close to 20 foreign Esther that same PK is going to be about the same PKA for real and other compounds for the alpha proton but you get a special circumstances if you put to Westerners together we already saw last time but that guy half-full Maloney for example when
felicito acetate are extra setting and so you can take a compound like die Apple Maloney which now is extra said Act and the same just of the conditions you can go ahead and take this varying analyzable remember PKA 13 for dire for Malena a steel acetone no lying Ethel Oceano acetate 11 died careful Maloney 813 you wanna keep 1 number in your head just keep in 10 or 11 for all of these 1 3 died carbon you'll come from sector-specific of that your question intersected now let me give us justice minister of some diversity of money looking out high
school of year for new learned about aromatic compounds you learned about benzene but then you probably also read about all the five-member during aromatic compounds fear ran all the way to the fundamental ones for
fury and parole and Syafii and for the most part or all of those regimes like the fury and rain behave very much like the benzene ring so this is just another compound like thins out the hive Imagen mixing this kindly analyzable 1 a dichotomy 0 compound PKA
13 and fear for around and some dates of the the only difference here is I don't want use sodium hydroxide and don't want hydroxide anywhere because I vested groups if I use hydroxide and going to hide relies my ancestors and their carboxyl like so it takes only a matter side In ethanol another favorite solvent based combination you could just make it by throwing in sodium metal into ethanol very easy basis to make heated up if you like alright Delta here just to show you can heated up at the end even knows this looks very different it's all the same principles we just saw the
alpha-beta unsaturated Carbondale compound in this case and alpha-beta unsaturated 1 3 dichotomy or compound with a formed from a nominee realizable the behind and in the light of a highly Melisent come from West I don't great question can the Algol reaction form both the ANC components yes yes and no so for the most part under these conditions the Algol reaction is thermodynamic all different products are forming and were going to the lowest energy products particularly when you have something big like benzene this is much higher in energy because of steric interactions and so you get virtually none of it and so in this case were going to get you know so little that you wouldn't detected in cases where you had 2 things that were very close to equal in size and methyl group in an effort group got the answer is yes you would get both and this city so under some circumstances you might but for the most part it's pretty selective for most of the examples you'll see it's pretty selective for the geometry for the trans geometry now if you're hear molecule has to carbonyl groups and they're in the right relationship to each other and alcohol reaction can occur in the molecules in what we call in intramolecular outdoor reaction
In general 5 and 6 Member rings are particularly stable and particularly easy to form 3 and 4 Member brings have substantial ring
strain 7 8 9 Member brings have some other strain associated with them so in general if they reaction can occur in a way that gives rise to a fiver six-member brings it well let's take a look at
this 1 3 that this dichotomy or compound it's hexane 2 5 die alone 6 carbon chain with 2 carbonyl groups treated with sodium hydroxide and water from the favorite Algol conditions and the product of this reaction Is this cycle Tarantino now the 1st time that most students see this chemistry they look and they say all default complaint like Everett from everything I've seen before think about it said alpha-beta unsaturated carbon your compound you can look at it and say Oh wait a 2nd I learned these things former by way
of and in the light and the Cape Town let's see where does that get me back to to that gets me back to that's all that yes so what's happening on the condition of the reaction your forming he the said every possible position all more
of the analyzable side this Mathilde
broke the methylene group here the methylene group there and the other methyl groups some of those evil like just form reversible a others words utilized on the methyl group can go on to react and so in this particular reaction what's happening is when the
single life forms it can reach around tackle bravura and that takes us all alike and then the same things we saw before the out began working equilibrium protons are going on protons were coming off the out the light compartment if we mean elect light over here it does
have been reversal .period protons go on protons come off you can legalize here nothing happens but we knew it informed the on the other side like styles now were
also set up for that elimination we spit out hydroxide and we get into this thermodynamic well of the alpha-beta unsaturated compounds that has that challenges what's
your questions 1 on of the absolute so we generate some of this thing alive we generate some of this in a way it's all reversible so absolutely
disease-related forms but if it reacts informs the three-member bring that to straining 27 kcal per mole of brings trainer there about so it never site Wise's PGA of the key town is about 28 so think about it most of our species is the key town we get a little bit of this seemed like a little better than you know
like you know like they can react please keep generating more I'm going down this thermodynamic well until we've eventually all made the alpha beta and saturated wrinkled during let's take a look at a couple of other examples of the intramolecular Algol reaction what does have some fun here
so we did a 6 top-end Daiki let's do was 7 carbon diet he told 1 2 3 4 5 6 7 will take this 7 that carbon Niketown saying conditions are saying sort of universal Algol conditions in water we get here you go through the same thought processes and you get the 7 the six-member rate in general 5 and 6 members brings informed but say they are favored in other words in general we don't form four-member brings the 2 strained in general we don't often form 7 members brings try 1 more example here so now we've done it 6 carbon chain 7 carbon
chain let's taken a carbon chain these a real examples taken from real experiments that have been published this particular example just use potassium hydroxide and water instead of sodium hydroxide and water no particular deference no I said seven-member brings don't like the forms and now a member we form all these different lights we did equalize underside weakening relies on that side restarting toward the
methyl group here you imagine cycle I think form a seven-member ring as I said seven-member brings have a certain form of strain associated with them with eclipsing trains annular interactions they don't tend to form but if we utilized on them or substitute inside all of our lights form now when we envision cycle I think now we can form a five-member greater and that ends up being the product of this reaction you now this
process of thinking backwards again just apply it over here look at this thing backwards we have annual forbade unsaturated carbon your computer because you'd look and say OK everything that he said in class makes sense and then I get this problem on a tester an exam were quiz or work and I look at it and how you see it in the other direction so in other words if you say all harmonious emphasize this molecule from something that's less complicated that doesn't have a ring you say all like 2nd it's now forbade as unsaturated Carbondale identity
,comma from a died probably compound you walk and you say hi OK thinking backwards we have for this the view saying Wait a 2nd now you just go ahead and on that and you say I don't want that that's still has to when she was 3 4 5 6 7 8 he
turned his your carvings that's just that the 1st thing in the answer questions at this point you can have died teach owns you can have dialed the highlights anything in this manifolds really pretty cool alright this spring's me tell the
2nd topic I wanted to talk about the Michael addition injects calls at the Michael reaction Europe referred to as both ways but
that's just a fancy name for the addition of a nuclear file to the beta position of an Alpha Beta unsaturated carbonyl compounds we've already seen that key tones and the hides a very fundamental compounds now we've seen even alpha-beta unsaturated carbonyl compounds are very fundamental compounds and it turns out that alpha-beta unsaturated carbonyl compounds have special reactivity of the old so funding draw sort
of a generic alpha-beta unsaturated carbonyl compounds this could be administered it could be a key Tony could be now the height of the the sort of true general features of the reactivity the carbon materials as we've learned with Carbondale compounds is elected fell like the selector like the carbon
carbon but when you've seen this reactivity already in chemistry but it's also very active at the Bader carbon in other words it's also Elektra fell like no 1 we
talked about how to chemistry we said we can think about the
reactivity in terms of resonance as did we say what we talked about Carbondale chemistry so in general what we've said is all right you have some probably compound and we can
write recognize that this is the most important residents structure but we also know that oxygen is more electoral negative and carbon so even know they have a covalent bond between the oxygen and the carbon the sharing
of electrons you share electrons in the covalent bond you don't share elect to once quite equally the electrons spend a little more time near oxygen in a little less time here ,comma and so we can write a
2nd residence structure of minor resonance structure that reflects that reactivity some minor residents structure because the the carbon doesn't have a complete it's really not a very good residents structure it just represents a small fraction of a small fraction of the picture of molecule remember residents structures are at once they are the other it's not oscillating between them it's both at the same time but now with the double bonds weakening
wrecked we get right yet another resonance
structure also a minor resonance structure so I will write another reminder residents structure of the and collective late
this picture of these 3 residents structure is really make up a more complete picture of the reactivity of the molecule hot so the implications of the 2nd resonance structure their that the beta carbon can also react with nuclear files in a fight Hampton generalize it I'd say what we can say is that strongly basic nuclear files fill the
words nuclear files let's say well I'll tell you in a 2nd but let's say In general strongly basic nucleophile Allstate tends to react because this is all about tendencies so tend to react to add the party Neil moribund and I'll say it moderately basic nuclear files tend to react to the various types now waterway
mean buying moderately basic kit probably lady let's say conjugate acid would say has the detail of all let's say less than a room 15 and these are generalizations and tendencies waterway mean by strongly basic nuclear files are let's say the conjugate accidents that have the PGA of us let's say greater than or
equal to 25 and all deliberately leaves that that region in the middle for about 15 to 25 little bit vague that region includes the delights of the tones and the hides and to some extent they can
react in 2 different ways so let me let me give you then a concrete example of the Michael reaction we call the 2nd manifold the Michael reaction rethink borrowed this examples
from your text book just because it's a nice example when you get lots and lots of chemistry today and so I don't want overwhelm you too much let's envision cycle hexane known and its reaction with Ethel Acedo acetate under basic conditions of of the of but say sodium and fat side in methanol I've chosen sodium at dockside in ethanol because I wanted generated the you know later sodium at dockside isn't good enough basis to generate the in the light of a key tone around the height but it's specifically a good enough basis to quantitatively
depot made Ethel Oceano acetate remember PK of about 11 4 at Sollecito acetate PKK about 16 for ethanol so that equilibrium between sodium math oxides and Ethel the Western stabilize weight to the right the product of this
reaction but but but but but but but this fact right that he
is a lot a lot to swallow mechanistic glaze and so let's think about it what's happening so we're generating the inner light I will write the mechanism for that because by now you've seen this but many times we generate allowing eye can the debate opposition of the Alpha Beta unsaturated
carbonyl compounds we push electrons on onto the oxygen in the have a negative charges on the oxygen now we have a lot of lots of ethanol president but but but but but but but but but but but the human protons go on protons goal of soldiers can affirm the guaranteeing Malay the giver product you what's
your questions at this point OK I again
want to come back to to this idea of seeing because it is amazingly funny when you're sitting and looking at things in the forward direction and you say everything seems to make sense OK I can understand this week got protons coming on protons coming off we've got sodium at side is the base we about felicito acetate Ethyl you know as state is pretty acidic we generate that like we've got this Michael except after this alpha-beta unsaturated carbonyl compounds sodium method of a cycle hex you I know it's selector fell like at the carbon compound but pop and I know it's selected fell like at the beta
copy and I know that our nucleophile isn't so basically just moderately basic so we had to the beta carbon 0 yeah we generate e-mail late OK were in ethanol that he enlightened approach get and then you look at this In a completely different way
go-ahead weather along the blackboard going submitted on quiz or a test and I write something like that and I say How do you make it from simpler compounds and course I don't write that exact compound because organic chemistry isn't about memorizing it's about thinking your way through stuff and you say what the Holland had can I
see that and then you think OK wait a 2nd we've been learning relationships today we've learned to of them thus far we've learned about beta hydroxy carbonyl compounds and a light bulb goes on you say all I I see a bit of hydroxy carbonyl compounds he can't fool me nature can
pull maybe I can make it from an algal reaction you see alpha-beta unsaturated Carbondale compound and nature can't fool me they're eager I can make that from an Algol reaction with dehydration even if it's an intramolecular Algol crossed Alltel and so now we have a
new nemesis here we have this thing and you look at the relationship and you say OK what's our relationship it's further apart it's harder to see it's a lot and so
brave for all 1 5 dichotomy of now you just look at that relationship and you sell I already know the In a 1 5 .period die Carbondale compound I
envisioned a retro synthetic analysis where I break the the bonds between the floor 5 carbon
between the 3 and 4 carbon use that I go ahead I break that and you see backwards and you walk and you say Oh wait a 2nd that could have come with From the studio components and don't worry about reagents sir conditions yet in your retro synthetic analysis now the other
beauty of retro synthetic analysis is that you can see other things and all other relationships and this is the genius of organic synthesis because you look at this
compound and you might say called came on line C a 1 5 died Carbondale compounds to let a that of a number of like that and you look and you
say at all I'm gonna break the bond between the 3 and 4 cargo myself and
apply all my smarts about it being the bond between the 2 and 3 carbon that was the alpha-beta unsaturated 1 and the floor carbon that was the nuclear file you think about it the you saying apart all from the city this as my synthetic breakers and you look at that and you say here's another round by which I could possibly generate that Prop now
that compound doesn't look so simple I broke the first one into 2 parts and here I've only broken it into 1 and it looks kind of complicated but then you think again and you say Wait a 2nd I could say if this component coming from across
Algol reaction perhaps I don't know if this is going to work better writing ?question mark but this is the thought process I could see this company coming from a big cost Algol reaction where now I have a Quito the height and Ethel was you
acetate and maybe I don't know maybe I could convince Apple Latino acetate in a cost Algol reaction with this
key allow the high this 1 2 3 4 5 6 this year 5 Quito Hexham now to
1st make this component and then maybe I could carry out an intramolecular Michael
addition and that is the beauty of organics there's many ways to put together a complex molecules CEO on Thursday


Formal Metadata

Title Lecture 12. The Aldol Reaction and the Michael Reaction.
Title of Series Chemistry 51C: Organic Chemistry (Spring 2012)
Part Number 12
Number of Parts 19
Author Nowick, James
License CC Attribution 3.0 Unported:
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.
DOI 10.5446/19416
Publisher University of California Irvine (UCI)
Release Date 2012
Language English

Content Metadata

Subject Area Chemistry
Abstract This is the third quarter course in 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: 1:28-Enolate Formation 3:56-Aldol Reaction 11:44-Retrosynthesis Example 18:40-Original Aldol 21:32-Aldol Mechanism 26:45-Features of Aldol Mechanism 35:25-Aldol Example 38:21-Synthesis Example 43:16-Stereochemistry 46:46-Crossed Aldol Reaction 52:48-Intramolecular Aldol Reaction 1:01:10-Retrosynthesis of Intramolecular Aldol Reaction 1:03:16-The Michael Reaction 1:05:34-Resonance Structures 1:08:27-Strongly Basic Nucleophiles 1:12:52-Michael Reaction Mechanism 1:16:35-Retrosynthesis Example

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