Lecture 10. Enols and Enolates.


Formal Metadata

Lecture 10. Enols and Enolates.
Title of Series
Part Number
Number of Parts
Nowick, James
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.
University of California Irvine (UCI)
Release Date

Content Metadata

Subject Area
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: 1:16-Reactivity of Ketones 3:02-Enols 6:36-Enolate Anion 9:47-Enolates and Electrophiles 16:49-Equilibrium Between Tautomers 23:07-Acid-Catalyzed Enol Formation 29:18-Energy Diagram 37:51-Multiple Additions 46:41-pKa of Alpha Protons 53:05-Base-Catalyzed Enol Formation 58:56-Stereochemistry 1:03:42-LDA 1:11:28-Kinetic Product vs Thermodynamic Product 1:17:56-LDA and Stereochemistry
Meeting/Interview Lecture/Conference
Meeting/Interview Lecture/Conference
good morning so I'm
excited today we begin the 2nd half of the course today where Of course being yesterday his lecture will be on the so
OK usual questions but not seriously I'm excited because now
we get on onto the topic that I hinted back way and lectured to Weiss said that basically the bulk of this course is covering carbon your chemistry and even beyond lectures the 6 weeks of the clients we continue with the theme of
carbon wheels and very very ended a class where we talk about carbohydrates and about peptides and proteins but we've been talking for the past essentially 5 weeks about the electoral felicity of the carbon yogurt and now we're getting into this 2nd half of carbonyl compounds the fact that the
nucleophilic at the carbon under the right conditions 0 only bank in the 1st week I drew a diagram sort of like
this I said OK here's some generic
carbon compound not necessarily town roster we could around the highly threatening and Esther and a general just it is that the carbon down to select refilling the can react with nuclear files and now we come to this 2nd halves and so on I'll say now we bring this notion that the alpha carbon under the right
conditions can react as a nucleophile another words in react with
electric appliances and we're
going to be exploring this idea extensively over the next 4 lectures were going to be spending
this idea from Chapter 23 in your Smith textbooks to Chapter 24 and discovering the richness of the chemistry of Knowles Indiana switches the intermediates by which we have this
reaction OK so we talked to about
various aspects of carbonyl compounds structure and we said we
talked about the reactivity of carbon you'll come down we talked a little bit about in water equilibrium
with the hydrates species and we said that for example an innocent owners very little of the hydrate and typically it's not a big factor in the behavior in other words if I took an animal or a spectrum of acetone and water I wouldn't see the hydrate because it's just a minuscule amount of income well there's another
minuscule amount that can be president that's very important in reactivity and that is being all taught adverse all right in equilibrium we
we have and that's just take this is acetone right now will be going through with various examples but let's just pretend you have an acetone some town around the said should show we have achieved celebrity on where we have another species that now this species is
obvious very different in other words the Have you have the carbonyl compounds and then you have the species that has a double
bond ended alcohol and that's why it's called in Minot because he means a double bond and a well-known alcohol and so we referred to this as the he toward America and this as the evil .period Amir soak tore means an isomer where you've moved hydrogen around and
so you notice of course if this is acetone and here we
have 3 hydrogen is attached to this carbon and and in this particular all of acetone we would have to to hydrogen his attack and 1 here so that's the same
formula same molecular formula and yet a different arrangement of atoms 2 other murders are a type of
constitutional isomer remember we've learned about stereo areas and then we've learned about constitutional isomerization and by constitutional isomer I mean we have a different connectivity stereo isomers have the same
connectivity is now as I said at the normal time whatever is in
equilibrium with the Quito taught America and adding equilibrium was way a way to the
left of tell you just how far to the left in just a moment but I wanted to introduce players now if we imagine
pulling off the hydrogen and of evil taught him another words indeed program removing that hydrogen with the base we get what we call and in the late and I have the honor the sort of set generic here in other words we could be acetone we could be something else but I want to show you that there are 2 substituent
attached to the carbon of the double bond there to the to what we
call the alpha and the inner life that I can be thought of as having 2
different residents structures so we can envision 1 resident structure
where we have a negative charge on the oxygen and a 2nd residents structure where we simply movies electrons down and move the
electrons onto the output member we
used the double-headed arrow not a reacts to narrow mountain equilibrium error but a double-headed arrow to indicate residents structures and I will be very explicitly all my long years since draw my
negative charges like and just to be a good person and I'm going to put this in
black text mind asked to help remind us that these
are 2 pictures of the same thing it's not 1 of it's not the other unlike the key all and in all part of our there are not 2 distinct species that you can identify distinctly they're 1 and the same at the same time and so I will write resonance
structures here remind us of this and I will also remind us that since this is an alliance of energy in always College and no later and I alright and these
2 sets of variants on the carbon the in all
taught America and the late and I never going to be occupying our thinking for the next a couple of weeks for
the next 4 lectures as we explored the reactivity of carbonyl compounds and specifically the ability to react nuclear files at the office ,comma Wearing in
terms of understanding reactivity in this reactivity is nucleophile so I think the Hina late a very obvious place to start so if I do on the structure of the late like Sony and again on keeping it kind of generic you could think of this as an incidental later you can think of it as some other you laid by the
fact this is pretty much universal behavior in the late and we imagine
some electoral file now again in the spirit of keeping things in areas that are going to write it and see what's that doesn't necessarily mean we have a positively charged species you've seen positively charged electrified as you've seen
cargo Qatar hands in the past protons or age 3 0 plus of course are cat ionic collector files but by the end of today's lecture he'll also be seeing
methyl iodide in Essen to type awaiting agents acting as electrify also here in various cartoony very loose fashion all right he plus implementation and every activity at the Alpha carbon as
a nucleophile can be thought of as
bringing our electrons down from the oxygen bringing our electrons over from the double bond over this to the added there I have positive charge against technically if I want to do this duties right made
my airline should end up at the Adam and again
this is sort of an abstraction of an atom in so on if I won a complete drawing that
constitutes our reaction now if you're not comfortable with
moving all of these Kerberos around realize that this is just the representation that this 1st part of moving electrons down and moving these electrons is
just the embodiment of how we get from the residents structure on the left to the resonance structure on the right in other words when major converting these 2 residents structures in my mind's eye on bringing
these electrons down and we need these electrons onto the Alpha carbon but I don't necessarily need to draw that out because by this point in my costs and by this point in your thinking you should be be comfortable enough with that operation in your mind OK so that constitutes the reactivity of know
and I just wanted to take a moment before I take questions to talk about the the reactivity of the Knowles again
over reviewed in this very very generic fashion so in the case of we know this morning species that's present in equilibrium with key towns and now the hides and to a lesser extent with other compounds we can imagine here are you all and again I'll have my engineering electrify all the lost and we can imagine electrons flowing down from the oxygen this is
heavily carbon-oxygen by giving rise to a carbon-oxygen
double concurrently with electrons flowing from the issuer carbon-carbon double life should be electrified and if we continue without the glamor of electrons Washington glamor of the curved and but now that's going to leave us with a protonated carbon but in a bowl and you
are electrified and now we can imagine losing a proton again I'm talking very much in
abstractions here so I'm not talking about a proton just popping off cut protons being taken off 5 days and so
at this point we can imagine going at it said that in 201 and all right that Proton in quotes because Indian 1 with the regional something taking it off
so we can envision getting into the carbon your content that's react at the Alpha chip question the government of the can the
negatively charged carbon absolutely it is 1 the same whether I write this reaction as the flow of electrons cycle or whether I
write the reaction as I guess again technically to be correct since it's a resident structural going to write it in the exact same geometry what the exact same geometry because the 2 residents structures share geometry
felt that if I want to think about it like this this is itself
a I think is the exact same way of life in this and so these are not really different here just
different ways of representing the same thing and as 1 moves in their understanding of organic chemistry you
go from sort of needing to explicitly right that latter 1 out to recognizing that the 1 image embodied in the former which happens to be the major residents structure the 1 image embodied in the former ends up being
enough for us to think away other questions barring
let's move to some specifics is this provides an overview of this provides a very generic introduction to the chemistry of the Knowles alliance and now let's
talk a little bit about some specifics about the prevalence of because of all the Carbondale compounds with the exception of dying carbon meals which were
going to talk about very soon in a lecturer itself with all the carbonyl compounds out of it's talents are the most in your wallet Ronaldo heights being a little bit more and all I could think he your text but just give the sort of a generic answered that there is less than 1 per cent president for a typical carbonyl compounds but it's a lot less than 1 per
cent there is very little in all so acetone he is equilibrium that
used for acetone under glass where you're spraying mostly acetone but you're sprang a little bit of acetone in all it's an equilibrium in the position of that equilibrium pays equal to the delivery and
constant is equal to 1 . 5 times 10 to the negative Saturday in other words
there is less than 1 part in a millions of acetone in all president at equilibrium
cycle hacks acknowledges in general more substitution makes for a more stable double
on we learned this in the chemistry about things that in general when you put alkyl groups signed a double bond it's more stable so cycle of taxes exists in equilibrium with the in all and it's a little bit more In all like that acetone the equilibrium constant is 5 times into the negative side again just that here more than 1 than a million workers
before August here last .period part as I said in general outlines are a little bit more and all that the the towns that's not necessarily surprising Remember the Alamo hyperbole group is pretty darn
unhappy as a carbon group it's only got 1 alkyl group donating it we thought that's what we talked about the chemistry of hydrates and we said that acid alcohol I exists about 50 per cent about half hydrate and a half as the elder of pride form water whereas acetone is vastly predominantly the key to on-form not the genital and so similarly we see that as set out the height is a little bit more and more like say acetone which would fight the the best comparison so when asked about the higher you wouldn't have an equilibrium again at equilibrium wise way way to the left but now you have to do just that here in of the yesterday of the tribunal the equilibrium is the 2 times 10 to the negative fight for your equilibrium constant compared to acetone the couple orders
more orders of magnitude more and the inspite of being a minor equilibrium ,comma opponent the
reactivity of also is very important in the reactivity of carbonyl compounds and I make sense even if you have a little bit of something when it reacts mortgage generated and sold reaction can proceed and receive any proceeds being small doesn't mean you're unimportant and so we can take a look at how we can also in key
towns Quito Indian all taught emerged eager converge and look at the the mechanisms of formation another question that so where will orally
or in the a world of the Parejo one-step who wants to answer this question someone you know all form of mouths and
can intend no althought carbon non-formal the Hyde Park
were on the best the so I would hope and that's a
very good way of thinking about it whenever you have an equilibrium you're
comparing the energy of a ground state and product and tho the bigger the difference in energy the bigger the equilibrium constant the bigger whether it's positive or negative depending on the weather it's greater than 1 less than 1
depending on how the energy difference goes so anything that either lowers the energy
of the reactants war raises the energy of the product makes that equilibrium constant greater in magnitude whether it's in only 1 direction or the other direction so when
we talk about acetone versus site while hacks known they're both the towns but were lowering the energy of the in all by making the double bond more stable so here is the
acetone in all here's the cycle and only not in the case of acid out high versus acetone now you can think of it as were raising the energy of the reacting because acetaldehyde is hiring energy it's less stabilized relative and it's always a question reference frame but that's a good way to think about it so later on we're going to see things that provide a lot of stabilization of the you know specifically countries are so that's talking about reacted and about products about Tito and you know
all taught various let's now look at how we get from the Quito taught America to all and this reaction can be dazzling catalyzed by you the acid or
base I wanted start off by talking about finances and analyze the formation and I don't write out the mechanism various slowly and carefully very meticulous late
because I think this really is important to think your way through we've already seen on the way is how important mechanism is in
clarity in expression and thinking on mechanism the mechanism on the quiz was kind of a long and complicated involving many steps the mechanism
of acid catalyzed all formation is relatively simple and easy if you have an answer to Padroni a mile on for example
protons go on and off everything with long pairs of electrons at Carbondale of acetone the meal of a key tone of the of an ester these weekly Lewis basic weekly bronzes basic and so you have in equilibrium where you can quote me the company also about the apparent the
looking at my draw near my honest catalyst Pedro pneumonia and has been consumed in the 1st step of this reaction and now we're going to recreated in the 2nd step of the reaction I'm going to
have been drawn up program made it as its own and now I will explicitly drawing in my help a hydrogen is because we're going to use them very
often when you're writing a mechanism were thinking about a mechanism you will write in different parts of a molecule that
went line so here's our water here's our alpha proton and now Water is weakly basic very weakly basic water can pull
off the alpha proton creatures
questionnaire electrons up a lot To the oxygen and again we have an equilibrium and I will be very very explicit and try to draw on my all of my relevant hydrogen is here to help keep us on track I will
try to remember all of my movements here as in all of my charges showing not a bad person and here we go that's that's an example of how we go from Iquitos taught to the King of Pop I thought Sir
questions at this point
His water able to call off the hydrogen cells so you mentioned the term additional elimination and we've seen
additional elimination innocent chlorides that's worth nucleophile adds to a double bond we pick up the lone pair of electrons it comes back and questions something out
nucleophile fighting Amin adds to an acid chloride we kick electrons off onto the oxygen they kick back down and kick out the court so this reaction mechanistic is an acid base reaction and the only thing that's that's made a surprising were confusing to you is the fact that we're continuing to push for electrons all the way up no technical in the technical area I could go ahead ends
stop but but but but but at this point but of course if I stop at this point I recognized in my mind's eye while this is a really
really funny residents structurally really unimportant bad residents structure but but
but but but but from there and so we just keep pushing and of course protons come on
and off all different specific positions innocent face equilibrium and so the proton works I forgot my positive charge so much for the utility
person over here so
the protons can come on and off the oxygen and then we had the reverse pathways and guess what most of the
time your equilibrium petitions that in other words when you have
an equilibrium like this but of all the years our
energy here's a reaction toward net when you actually action like this where we're going from react firmer acetone applies aides Rio losses 2 are appropriated acetone and then to the you know all technically if I'm writing this out collectively this is acetone .period needed acetone was staged to love what's happening in our mechanism is 1st we're going out to an intermediate and then we're coming down to our product during all that's higher in energy so when you're at this point at the
intermediate you can petition that you can partition forwarded it goes both ways most of the time it actually ends up going going back down and ultimately of course it's the difference in energy between our products and our reacted that determines the position of the equilibrium there was another question you know what
the violence it does
indeed take the age from the oxygen and the mechanistic reversal of this step is taking the lead from there most of the time it takes the stage from some of the time we go forward and it goes in the other direction or should I say well it's not technically the
petitioning it's not going to be most the time it's going to be the half-and-half because most of the time without forming this intermediate so technically technically can
be a little more honorable than the other but the point is that heads back sometimes we pull off this Proton
and heads forwards this Proton is Mississippi but the question of what I can
the water also perform a nucleophilic attack great question this is like so profound This is
why people can find organic chemistry confusing because yes it can and yes it does and we saw that we saw what we talked about acid catalyze hydrate formation acid catalyzed Germinal dial formation so in your acetone in water with a little bit of about answered honestly even without a little bit of acid because water has had only a minor tend the negatives 7 bullets in your acetone and water there is this dimension this mixture of acetone the main component and then a little bit of the hydrates and even a low and even less of the inn also absolutely and so
keeping this in one's mind all yeah this is the pathway were thinking about now because this leads to the good stuff we're going to see over the next 4 lectures he is often confusing to initial 2 beginning students great
question really important because this is the part of understanding at all and you look at this mechanism
here this manifestation of catalysis and realize what this means for the on catalyze Methodist it means that in the long catalyze mechanism you're not actually changing the
difference in energy on trying to block this curve for the UN catalyzed mechanism between tennis at all and acetone in all at the exact same level you're not actually changing the difference in energy between acetone and half the all what we're doing is
providing a low-energy pathway that's not accessible without asks another word here is right but that it plays a one-step
mechanism that converts after tone to acetone in all but
the energy barrier is much higher so when any answered is present that includes that tend to the negative 7 smaller rates the Rio plus i'd Ronnie
Amon pure water of acid can catalyze this reaction now the
other thing and I've been beating on this beating on this like a dead horse and the other thing that's important is
reactions per se through there were the reverse reaction proceedings through the exact same mechanism when Sianna hydrants formed by adding cyanide to a carbon yield to give an Oxy and then appropriating the Oxy and I had to get the alcohol we learned that Sianna hydrants break down under the
same conditions by the program aiding the oxygen to give an and iron and then kicking out sigh and offer kicking outside the also formed by 1st product noting the Carbondale to give appropriated probably compounds and Andy program dating the Alpha carbon to give legal that means that the the reverse pathways proceeds backwards by the same mechanism and so we can write and you should
be able to write in your sleep the reverse mechanism we simply go ahead and start with you all In a Lonely environment the protons float that Proton goes to the Seattle carbon electron slowed down From the oxygen but for now
in the 2nd step that's the step in going from our intermediate and water back to our acetone Maryland water just
acts as a base and told all the protons on the video electrons from flowing from the lone of water to the protons to electrons in world so the flow from the bond backed up on his reaction to the
what's your question Our at
saying where this gets us in terms of summary activity it will directed mainly to get really bad Our
undertake probably the simplest simplest reaction that I can think of another reaction is going to be a duration of solid-state cycle had
known as a variation here and while envisioned
dissolving it in detail while (left parenthesis as solvent D to always just heavy-water
it's just deuterium oxide it's just the isotopic murder of water with deuterium every glass of water you drink contains zillions of molecules of
deuterium were zillions of deuterium atoms 1 out of every 7 thousand hydrogen atoms in deuterium and natural abundance meaning in your proteins in your lips it's in your carbohydrates there is a minuscule amount of deuterium and 1 can buy electrolysis or distillation concentrates the
deuterium to get pure 52 if we treat our cycle heck synonymous with the two-hour and a little
bit of political answered I'm going to get away from H 3 0 plus 93 0 plus 4 is 2nd to remind us what actually has to go into the laboratory and get a real compounds I've written DEC LDC Alice just hydrochloric acid made with deuterium to adjust strong acid it associates and the 2 0 what will happen is you will replace all of your alpha protons With deuterium and this is kind of cold you could see this for yourself if you ask
your led to yank To give you some cycle incident the too well and a yard and a little bit of the a dissolved your cycle Hexham in the 2 0 0 you would be able to taken on a more spectrum and you would see the alpha protons that hydrogen is next to the Carbondale at about 2 and a half parts per million and has the reaction proceeded the peak in the animal from those hydrogen is the peak at 2 1 their parts per million would disappear as those hydrogen swill replaced by deuterium however so how
does this occurred while it's the exact same mechanism that we saw before just repeated over and over again I'll write this in abbreviated fashion we can envision that 8 indeed to all week protonated D 2 0 with the Seattle remember when you pour HCl until water you have H 3 0 plus and cl minus the daily three-hour class is just like H 3 Alpha lies in its reactivity you can put a deuterium onto the carbon to to give a a protonated were in this case due rated catamarans and now in the 2nd step of this reaction of course on balancing my equation in my 2nd step of my other product is In the
2nd step of the equation just as we have all the protons off the alpha position of acetone with age to of appropriated acetone now the deed to welcome Pollock are alpha protons and so
again we we have an equilibrium now we we take ourselves and you know all class if I want a
balanced my equation due to old age I think I will continue on a side here look but the effect of Arab so don't think I should point out
is we have lots and lots of detail well present water is 55 Moeller criterium is practically the same as as water indeed to always going to be essentially 55 mobile protons that and
saying again and again on and of
every parent native species from other words when we have a duty to old age class and lots and lots of water so I will write plus access for the duo you have been equilibrium and of course midsection drives this equilibrium and so you get a little debate throughout Asia Diaz it was three-year-old loss in other words basically you've got
tons and tons in the 2 0 your water just spreads out the protons just spread out to make a little bit of a date by dual reactions with 55 Moeller D too well and I
have of 1 molar solution or attend smaller solution of Tetonia as by protons go away and I get this little bit of show deep in this mass of mutual 2 and you three-year-old alright let's continue our mechanism here so we
have our all with
deuterium on it and we have lots and lots of duty-free all D 2 0 and a little bit of of the three-hour-plus reconvert made errors in all I'm just riding the same mechanism as I wrote before without with her narrowed even without killing in all of my lone pairs of electrons and now we did have further Proton further Deuteronomy transferred but for some the and you can envision this mechanism just continuing we form being all the
probe making all with deuterium reform in all more we protonated made with deuterium and eventually we washed out all of those analyzable positions and now
we have the full EU related molecules prevented Tennessee terribly bad balancing equations but if I want to try to balance the equation is the right way better keep was for the goes with catalytic TCL Indian to our salvation go to the only deteriorating the gentleman of but for the last quarter of the year in lots and lots of G 2 0
and of course the end hand of the but but but but but but at the end of this so 1 of the other properties of Carbondale compounds is that
the alpha proton is assessed so for example in names at all the alpha proton has a UK of about 19 and not centers because if you
think about it if you think about a regular
medical compound a regular algal compound but the area's 20 is about that in other words the people have an offhand is wild nominally acidic very weakly acidic it is very very very weakly acidic it's only acidic in the sense that you can think of its conjugate base being overbearing varies from place and yet by the time you get over the acetone pointing at Carbondale their shares spiked 31 orders of magnitude the acidity of that Proton it shifts the equilibrium massive 1
because when I think of the conjugate base of acetone
don't just think of it as I think about that special residents stabilization that means yet as the inner life and you can say how picturing to
residents structures together the structure on the left is really very inadequate to explain this development the structure on the right explains it beautifully we have a negative charge on the oxygen we have oxygen is Electra negative we know outcome oxide has alcohols are reasonably happy to
lose approach on their weak acids but they're not very very acids peaking have an alcohol is 16 or 17 the decay of and Al-Qaeda's 50 that oxygen does a
heck of a lot and with acetone with our PKK of 19 we're getting a lot of stabilization from this resonance structure in
other words this is the major resonance structure this is the 1 that's important in determining the reactivity and this
1 is the moral stability and this 1 is the minor resonance structure now more generally the
Carbondale group provides stabilization and your textbook gives a number of compounds of giving these compounds and and I wanted to give you a generalization that I keep in my own so you
textbook gives you acetaldehyde lies
with the PGA of 17 and it gives you a velocity With the PGA of of 25 times for the methyl group renders you don't like free with the of 25 in the peak dimensional was undermined the PGA on the eve of the offer and really the
numbers that I keep in my head things are a lot of details but the numbers that I keep in my head are as follows I keep in my head to numbers for all of us that the alpha proton for the Keatonâ now that my family are
about PKA 28 but the of the twenties good enough yeah keep in the back of my head out the hides low but more acidic while keeping my mind that 20 is typical for say cyclo Hexham known that acetone is 19 and that delisting tells the small those around him was the big picture while the
hides in the tones Europe-bound PKA 20 in general the carboxyl like acid families esters nite trios even hammered even carboxyl like acids under the right conditions in 1st remove the acidic Proton so it's a
carboxyl light and then you remove a 2nd protons in general a good number mine is about 25 yeah there's some
variations but it's not as simple importance as keeping these pictures in my life and 1 of the pictures from this is that in general Key tones and
enhancing a penthouse the hides armrests said then water no other words hydroxide will take off only a small amount of the protons only an equilibrium
concentration and dockside will pull off only in equilibrium concentration but stronger bases closed and Pollock protons quantitative but the thing of that since the alpha proton so that the tones and now the hides it shouldn't surprise you that
dates can also catalyzed in all formation so let's
come back let's come back
to our acetone molecules as our sort of archetypal the
tone and now let's envision
hydroxide as a basis for making this without cannot decide to let some sort of moderately strong base not stupid things were strong with talk about super super strong in a moment but something like hydroxide or and I mean like try Ethel Amin we can't pull off the alpha proton me
out for Proton is weakly acidic remember PKI
of 20 years the number you wanna keeping your head should be happy that he will bring me here the Lane but at the heart of but that equilibrium
why slightly away from the inner light and so we can progress in other words you
generate a little bit of being but that you don't generate the Lake quantitative like is so we can probably native reproach laid back and carbon were headed back in the same position were headed back to the start of the reaction of it probate on oxygen and on the other hand now we proceeded on the show but but but but but but but but but but but but but but but but but but but but but but but but but but but but but but and just as
in our acid catalyzed Nall all formation of hydroxide here although it's is being consumed in the 1st step is being recreated in the 2nd step and so
it is not being taken up water destroyed or created the reaction overall is acting as a catalyst similarly were not changing the
position of the Quito we all equilibrium where only creating a lower energy pathways to allow I think he's shown in all forms to induce cancer 1 the only solution the work you have to buy it I have
very good good question if you're working very well every hour technically yes in this particular example that is an astute questions in this particular example with these protected the PKK is technically you're right there will be more know life then you know all presents if you want to
come to an example where now you have very little in light and equilibrium still goes substituted this reaction as base triathlon because now we remember we said that for
acetone were going to have 1 . 5 times 10 to the negative 7 is are equilibrium constants so there's not a lot of being away and not what we know and we're having PKA
for acetone of 19 of which means you actually do have you know but 1 in a thousand 1 in 10 thousand you like the 1 in the thousands so if you substitute try Ethel Amin PKA about 10 or 11 for the conjugate acid you'll still catalyze this reaction but now you
have very very little of the
inner life do you use Indian stock apparatus no need here were not actually trying to change the position had caught
1 year now you're asking smart questions had 1 this reaction and the answer is you can't private by removing
water because the reaction is unique molecular overall there's no net change in the molecule into summarization of the waded right the reaction to the you away is to go ahead and to on the use various
strong Bates and unfortunately there very little 1 can do to to try not to generate the mall was an isolated species although there is an Israeli chemist to actually is focused unstable because another thing about organic chemists in
addition to being very bad at balancing equations is there someone says it
can't be done Penaloza unstable you cannot make a stable you know all you get decked you inorganic chemist go out there and say how do I make a stable where
you know will stabling All-Star especially novels but the regular 1 hour some somewhere all of this leading puts you go and do something like this canisters so
just like Alan D. too well if I take all with catalytic sodium do rock just the deuterium analog of sodium hydroxide the 2 well as solvent and I let it set again you can do this for real and and a lot of Johnny European could go back to my laboratory in doing this right now and so you those out of protons will wash out and be replaced by a deuterium similarly imagine's for a moment that I had something that had morality of the animal from opposition led Samoa managers for a moment
that I have this Tetonia where I have a metal
group and let's say that I have just the acid into and I treat this key tones well let's say
sodium hydroxide since we're talking usually chemistry sodium hydroxide in water then what will happen will bring I'll lose
my an anti-American purity and I will get a mixture of the 2 in the words I will get the ransom made I will get an equal mixture on the hour and the US what's happening here in
this latter example were forming will bits of building like repeated on the amyloid
is flat the light loses its plurality we have to do it here but I will say that we
don't want this the words you can picture in
your mind on the basic pulls off the alpha proton we get the inner life the alighted flat we have no power reality to the inner life if a proton comes from the back we get the original anti-armor if it comes from the front we get the new and America and so
are compound last symbolizes a we estates but the
because of the but but but but but but but but but but but but but but but but but but but but but so in addition To being
battered balancing equations in addition to wanting to do what can be done organic chemists are control
freaks really wanted control of molecules and make them do stuff and often we wanted do stuff mixed up it's useful like new medicine itself whereas weak base doesn't make a lot of communal life a strong base does and we can use that if you have something like
cycle Haxtun only in a big piece of writing that you -minus let's say invariably strong but there is no other words PKA conjugate acid much greater than 20 then we have an equilibrium that lies way way way to the right often so far to the right that we can just ignore the left arrow through the advised the you know laid an the the report needed In the
base that's extremely valuable To organic chemists is dying
Isa problem and I know more specifically the lithium salt within diaries of probable and ended with those last year control rates for those of us who wanna make molecules do
start this place is really good guys it's a stronger take care of the conjugate acid the PKK headed for
dioceses bowler Maine is about 40 cent of people at find the R 2 inmates is nice
shorthand and Allstate until the day of approximately 48 member were comparing notes that if you
want the 1 number in your head the 20 for the week Of cycle except for the PTA fatigue syndrome that's actually the PGA of cycle of Texan known to within the unit but again just keep that number in your mind the other thing that's really important about the dice properly made I is it said the size of probable groups and the 2 of them are bulky they get in the way In other words lithium diets a problem it is a good day but not a good nucleophile and again I'm going to come down to this confusion in organic chemistry students when you're starting out Oh my God there's all this stuff the know-how to wine and all that this compound like cyanide is acting as a nucleophile Howell and all that I support problem there is acting as a base when you start to learn these patterns the very bulky ones are better at polling off of turns a little bitty once and cyanide adjustable when is better as a nucleophile so the reaction here lies so far to the right that are lithium late I won't even bother to write the the reverse arrow lithium Medieval II is essentially forms the idea story geometrical and of course the other process other component in this reaction decisive Pro Bowler so we have an acid-base
reaction stronger acid plus a stronger basis reacts to you we Déracinés plus weaker banks How do you know where that equilibrium lies
you just look at the case of the acid OK we've got the weak acid PTA 40 on the left and we have a strong acid on the right and remember the other number I like to keep in mind is about 10 orders of magnitude in other words
if you've got things would defeat a rate of about 10 units I'd say I have got a little bit of an equilibrium but you got 20 units apartments like have that reaction goes
essentially all the way but what about the but often when organic chemists riding out the synthetic reactions will ride in a little bit of shorthand for example I will say LDA widely used Internet provider of uranium as a solvent in order to
minimize its reaction is a nuclear file and minimize the full operation
Parsons often you do these reactions negative 78 degrees Celcius That's the temperature of a dry ice bath which makes it particularly popular member early on I said that was sort of an abstraction I said you'd see methyl iodide so you can envision a reaction like this in the 1st step we AD
Cycle hacks announced to LDA at negative 78 degrees in the next step we in methyl iodide no allow the reactions to warm up
maybe performing included worked up on it with a little bit of a little bit of acid and we've methylated Our cycle hacks and what's happening here say anything we saw with Proton and we've generated Argentina
late strike geometrically here's our
methyl iodide whether it's a proton whether it's methyl iodide we have a the like profile electrons flow from the Alpha carbon to battle of the electrical like medical carbon and you usually an as into displacement To give
methylated cyclo Hextall and I had died and I most of the time organic chemists don't go ahead and buy lithium guise of problem we typically make by acid-base chemistry and being
lithium is widely available it's the most common alkyl lithium of widely used you can mix it with ice probable Amin in th effort feel like people were you add your cycle hacks announced new Pollock of protons you get butane was lithium dies of probable admitted it and again I'm now getting into writing things ensured the hands-on not writing his many long pairs of electrons here and
this is an acid-base reactions and let the other is very very strongly basic that people care and how
big it is about 50 people and dies of mobile mean we already said his 40 that equilibrium wise brave way to the right you might ask why don't we use fuel lithium as a base comes back to what I was saying about security by using fuel at the at the main reaction the only reaction that you would
detect that you would write on say exam if you wanna get down to brass tacks of being an opium students would be edition of the bureau with To the carbon
not satirically hindered enough tonight aren't we goaded lithium Dicer problem with those big eyes probable groups and now it's much more basic than nucleophilic that you and your lithium toward a carbon meal is much more nucleophilic standard is based the company 4th of art
and said some fine now with variations among among know so the
magical Willie the government also like well
Hecht's about it we treated with now we can get to different people we've got 2 different types of alpha proton we've got out of protons that are opposite the Mathilde an hour from protons that nexus of methyl another
words which means that this the light but the more we can get this in light of the less substituted in light wore the more substituted like now but being General we know there were substituted double bonds are more thermodynamic police state the more substituting light is what we call the thermodynamic at the lower in energy monument equilibrium between the 2 Weiner like it would form but we also
know that size matters we have ball in the side of the molecule that we have not helped the side of the molecule the base particularly hysterically hindered base needs to get into Pollock approach on its standards for have been easier 1 of its Paul so the accumulated that
is less substituted is often referred to as the Connecticut and the like the 1 that performs versus the 1 that is easier to form so we can go ahead and think of it as but the EU's protons and more accessible but this
pro timing is technically a little bit more acidic however right
here but at the start of
comparison substituted at the leniently but more people in the modern and stable so let's take a moment to play with this notion because as I said
organic chemist loved to control reactions of love to control reactivity and it's important because when you're making molecules for medicines refer drugs you need the molecule that he was not take a couple of
examples of this text of yielded his good examples if we take on Apple's site while and on and we treated the LDA In the Newark Chaput negative 78 mostly with Justice LDA you may
see a Britain LDA th Demaci of Britain as LDA
ths negatives of the and was treated with methyl iodide read deeper pro-trade to warm to form the kinetic Pena and we end up with the 2 sects Diamant full
cycle Hecht's and also all right viable
committed the following an example from your text books which if you want to ask questions about after class I will tell you some of the subtleties of but if you trade with a weaker base that can equilibrated abbreviated text uses sodium at dockside in ethanol and basically the wearable right this is the mixed sodium at dockside methyl iodide even ethanol
there because we're under conditions where recurrent inadequately equilibrated area light your predominant
product your main product is going to be bit to two-dimensional hypertext and owned by the government and I'm away and so
this is the case of the type of control that organic chemists can get now right this is a major product
technically here I do this reaction with LDA this is a major product in other words I'm going to get 99 parts of this and 1 part this technically this is the major product Albright get about 80 parts of this and 20 parts of that no there's
1 question but I want to wrap up with a a couple of last week's events Theriot demonstrating and spirit of the summers at this point because I think it's I think it's pretty and I think it's cool and I think it's intellectually and I think that a lot of this is what
organic chemistry is all about so technical I'm
lying in that structural maybe to be more precise I'm
telling you have story and the other half of the story is when I want this structure and living in flat Lyons each of
those problems with the methyl group is a superior Gen-X center and so we have different types of species
that we yet but we have this species of this theory all over America to be more specific in which the 2 men are on the same side of the range we have resisted serialized Samarra that we have the stereo Isabella in which the 2 methyl groups for only the opposite side of the ring which went in there and so when we form of art the life of the knowable specify my methyl stereo demonstrated environmental groups the ads from the back of the net the trends there away some environmental group from the broad some of them from some of the people we get this sterilized the but but but but but
but but but but but and there's 1 more level of subtlety of show you that there was going to ratify the selection so
amendment for a moment I take this compound and almost invariably way it's going to be rescinded if I haven't specified under conciliatory without interior but negative 78 degrees and I treated with methyl iodide just design .period and you get a mixture of this isn't France compounds but of course the trends compound this is going to to be the receivers but no other words we generate real life and the methyl group if it adds opposite
methyl groups depending on whether this methyl group is out of or back we're going to get in the vicinity of him In the case of the status this says ,comma out of print ads from the same face this this
compound is a means of communication so in other words whether I draw like this all right Vermont like this this is just the cells in the article that gives us a taste
of the richness of stereo chemistry as well as the beginning on this
notion of control and you can't say even we've talked at this point about control of the region of chemistry of edition we've only seen that there is still a depth and richness to the Styria chemistry of efficient and that will go largely beyond the scope of this class thank you


 1472 ms - page object


AV-Portal 3.10.1 (444c3c2f7be8b8a4b766f225e37189cd309f0d7f)