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Lecture 14. Anions.

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Automatisierte Medienanalyse

Erkannte Entitäten
I want to start off with and so today
we're going to talk about an on and really were like about his proton transfers it's a way to get to an irons and then think about Proton transfers and maybe the nuclear felicity of this species you can generate an ominous start off by talking about what ought to be a trivial mechanism this is the kind of reaction and soft organic chemistry textbook and that's talk about this mechanism because it's not so simple it's kind of stunning that this is the kind of thing they ask the introductory organic classes on and proton transfers are important at every single step in this reaction even starting off at the 1st step of the mechanism they have to think about the things that have to happen here we gotta get some sort of an oxygen nucleophile to attack water at that carbonyl group we have to somehow get those fan oxide affinity group that to a certain kind of estate words willing to act as a leading and that relates to pretend transfers so right off the bat we've got a question what we do 1st the probe make the carbon Hill 1st like a fish's verification where we attacked the carbon Hill was a particularly easy kind of carbon Hill to attack performing Esther much more reactive than regular restaurants and so how do you decide so noticed I last year for the mechanism I don't do that on the problem sets and on I don't see what's the mechanism for this reaction I've never done that I was ask you what is a plausible mechanism for this reaction that's all I'm capable of asking you and that's and capable of evaluating so heartily decide which of these 2 starting steps is plausible you choose the wrong starting step directs to be mechanism will be garbage if you picked the wrong person you get to the next stage of the reaction you're nucleophile ads in then you have to decide how how am I going to get a proton off of here and get a proton on the financing groups that I can now push out that cannot say leaving group show come along with my acid and probe made the leading group like this and then use and then come along and deeper the water permit the water 1st right these 2 steps that we need to transfer a proton pull 1 off put 1 on In 1 do we do that we you decided that kind of stuff How do you look at those kinds of pretend transfers and decide if there are reasonable and so let's talk about proton transfer equilibrium that's how you decide you know something about the equilibrium of Proton transfers all 4 of the 1st of all what was be 1 the of the things so 1 of the things we had intellectual we talked about pretend transfers and I tried to get across this idea that you should assume that Proton transfers of fast you
should assume that all Proton transfers are faster and faster antiprotons France arrived on here you should assume it's faster and faster and so it boils down to not is
it possible 4 of the Nazi lone pair to pull a proton officer massive yes that's possible yes it's fast what you should ponder is is the equilibrium for that process good so Alex talk about how do we estimated equilibria for probe nation of Minister for nation of anything and I'll give you 2 ways to estimate the equilibrium ratios and that we care about its ratios the intuitive I have 10 times more money than I had yesterday I a 100 times more electricity running through this wire we think about ratios that's easy to think about OK so I'm going to give you 2 scenarios where I expect you to know how to use PKC onto estimated ratios appropriated versus the permitted species and I'm going to start off with buffered conditions so pure chemical biologist these are the conditions that should matter most to you you got some sort of buffer that either soaks up a delivers protons in order to keep the pH constant and electron tube buffering lines are President large concentrations
relative to the substrate so they could take an example this'll be a very organic molecule memory biological but the point is that when you're under buffer conditions you have to pay
attention to the pH of the solution candy probe nation of this of this Nitro key towns very acidic so Tavis nitro group but the Alpha position which is already certified by the Kerviel it becomes way more acidic when we had the nature of the and it turns out that this that these protons here at the peak aviator that's the peaking those protons and so what's the ratio of protonated did the solution is it reasonable for me to predict that I'm going to deep probe to making only online and that it then I want and I is going to attack well it depends on how much is in solution if there's a lot of it then yes probably reasonable that that's a nucleophile floating around that there's very little of it well then maybe that's not such a reasonable mechanism so the way you
decide what the ratios of these are as you have to know something about the pH and here's the way that I do this I'm going to make a little chart here and we'll just imagine that I know something
about the pH of the solution me make a list of pH is here and I would expect you to be able to estimate the equilibrium ratios in any of these peaches but there's not pH which it is on which it is easier to estimate the equilibrium than any other pH and that's when the pH is equal to the PKK that program when I when I'm looking at a solution that has the same pH is the peak my program I know for a fact that the ratio of these 2 species is 1 2 1 at pH so I know the PKK and I know the pH of my solution I can readily they have this sort of intuitive sense for what's going on behalf of my substrate and there is the problem is that's a lot of people native stuff this was not what happens at pH 9 if I if I make a pH 9
buffer what happens to this ratio if I don't Aladdin repair of Buffett's PA shines steadily it's 1 attacker
when I go up and pH by a factor of 1 this is this is logarithmic here I hope engaged by factor 1 by solution is 10 times more basic so right that I should be totally intuitive you now that there should be 10 times more of the deep-rooted needed substrate and now what happens if I go to pH tent this is the kind of man I know how to do I expect you will assume the duties government announcement 100 that's about 99 per cent I don't know how to work the math exactly but I would say that about 99 per cent deeper only about 99 per cent of my Keaton is actually you later pH and nite now I can go backwards weapons like the neutral solution but suppose that I'm interested in physiological conditions closer to pH 7 what's the ratio there so now it's
tend to want despairing that deep probe made inside and favoring the neutral side only about 10 per cent of my substrate and there is
exists as the any notice I don't care at all about the mechanism for deeper nations were assuming all that this assuming proton transfer fast don't get caught up in worrying about whether Proton transfer G should I draw their aerial it's always a good area to drop proton transfer occurred there In the issue the equilibrium and as they become more and more acidic by factors attend you can see what's happening to the amount of on the the from native species becomes larger and larger so I expect you any time you know the PKK of a lysine side-chain assist violate any sort of speech of phosphate group on DNA I expect you to be able to estimate the ratio of cremated deep-rooted the most commonly
at physiological conditions but in any buffer that you're getting expected to have an intuitive sense for only physiological pH About . 1 % a license I change
exist is Bria meaning that a long period intact and that's the kind of intuitive sense that like so there's some equation called the Henderson household market which I can't even remember the equation that somehow or another you can give these numbers out there but I don't know how to do that so if you can work out equation ,comma this intuition In good OK so that's buffered conditions sets for chemical biology and there's some organic reactions were you buffer things not so common so now let's talk about on buffered reactions this is organic synthesis the people of the hydrolysis minister your working up some Beutel in addition formal clamor Aldo reaction John Buffett reaction conditions that you set up and putting year-round bottom
Westminster that we deal with this it's totally different now so and when they just give you this simple
generic equation for a proton transfer like this but we feel like we've talked about this already but it from China can remember aware that we've talked about it and there's a simple equation that I can use to estimate the equilibrium constant for any proton transfer and I just need to numbers to estimate the equilibrium constants were not argue about whether it's easy for this the poor Proton aren't you should assume that always vast what you need to worry about is 1 of the relatives concentrations of these species in solution OK so it's good to be more proud while I gave you some sort of equation here add even scared of equation because the equation is so much more complex than actual Matthews to solve it looks something like this the equilibrium constant for any pretend transfers he called attention to the PKK above I I do
this the product of minus the PUK of the reacted to all of and that looks so complex it scares me so it's going take a real example so I don't get too
scared by those that kind of complex equations and serious reaction it wouldn't work under buffered conditions very well on this now we're looking at making any delayed late by using a strong basis she'd Utah oxide to pull off a proton should be getting TB acknowledged a byproduct and there's a potassium iron floating around a worry about that will be our next lecture had a deal with that and so that's the way I would work this equation the equilibrium constant how much of each of the species do I have president solutions In other words were not going to worry about whether whether it's plausible to draw deep probe nation We're going to worry about how much of that deeper native species is that their some there are much less an hour going work this equation the
PKK for this particular Quito on and I'm getting numbers for DMS so I happen to be the solvent for this reaction Indiana so I'm giving you no good P case for this at 24 . 7
for the key towns will talk about the sole issue here and 29 . 4 for the TV and those are the people gave Indian itself and so when I worked as equation I go like this the equilibrium constant calls tend to the 30 minus 25 attended the fair so what's the ratio of deep needed to prove native Is it mostly probe made it for the probe so favorably incomes like this says it's almost all industry now not almost all but it tells you that the ratio is tendered to the Fed missing 100 miles an
hour 1 to 1 that means over 99 . 9 9 per cent of this is exists in the EU lake form I get that just
released 2 2 PKK members here so don't worry about whether it's plausible to poll protons off with talks that were assuming that's always plausible but we need this sense that he and 99 . 9 9 9 per cent of mighty don't exist as the ,comma 1908 there's lots of it in my solution OK so that's the sense that I'd like it had no there's there's an issue here and that I want to point out and this this equation is completely value valid under typical conditions and that is that year equilibrium constant is only going to be as good as the PKK numbers that you throw in there so I give you an example where this reaction was Indiana so but you very rarely know the PKK case Indian itself or
ths or hexane zodiacal on thing and so what we do about that's what do you now and what will you know you're going to know that the case in water because
any idiot can do titration than water their tables and tables and tables of P Gazan waters somebody had directed the measured in something with fuel the failiure some indicator and they detect titration than water so what I'll tell you this don't worry about the fact it was that was the last it was that you've mainly only got out the case to work with used in many ways you may be a little bit off top will talk about where you'll see differences between water and an organic solvents even know you aren't you may not know the PKK in this all you work with you the water PK anyways will give you a good
estimate and a good starting point for me so I expect you to know ratios of appropriated indeed prorated thing is that every single staging a
mechanism where you got a proton transfer step you got to species and like you tuition for the relative amounts of those species in solution so I'm going to give you a set of PK is and I want you to memorize and there's no simple way around this you just need to memorize these numbers and more importantly I want you to know that trends that you can't predict the case for vast numbers of molecules that I'm not going to show you here but most of all of but it was so let me give you a sense of alarm PKC these are all aqueous PKS relative to opera solution summer extrapolated and so it could start of what I'm going to use I'm going drug groups of molecules so that we can see trends I'm among the group pieced together and I expect you to know these trends so the 1st trend I expect you to know the effective electoral negativity so let me give you a series of compounds here all start off with anything not compare that to me draw the same way to methyl amenable cannot compare that to methanol all I'm doing is I'm changing 1 of the so forget about the fact there's different numbers of protons on the alcohol versus the methyl what I really want to focus on is that I'm changing that 2nd Adam from carbon to nitrogen to oxygen I hope you already have an intuition that this Adam becomes more acidic as I replace that with more and more Elektra Nader groups I hope you already know forms from organic chemistry courses that
these are becoming more acidic going down this way and of those this is the most see what you may not know the numbers and I want you know those numbers the decay from methanol where money is the number 16 for an alcohol so
it's actually that's water that's most alcohols little range of the missile years 16 it will never hurt you it will be a case where you'll be said the use 15 . 2 or something OK so enemy the on enemy very hard to pull those off to pollute the that LDA lithium dies a proper Lambert is calling the proton off of this you get in 1899 nitrogen with a negative charge very difficult plot 20 orders of magnitude less acidic than alcohol OK finally get to a simple out pain there are no reactions in Elida deeper deep-rooted need simple out canes you should consider that to be the least specific type of proton that's out there so 50 relative to water 34 orders of magnitude harder to deep-rooted armed than than alcohol a
that lecture negativity so the 2nd type of trendy I want you to know about and I want you to remember these numbers would be residents at his residence effect the effect he did so when
he would start off with that at the molecule but instead of that name I'm going to attack to CC double bond on their personality program late this you'll have this Al and I so resonant stabilize L and I appropriate that level group as a whole would we compare that to and I mean verses and alcohol I am ahead and don't worry about the fact that there is a Quito Thomas it's more stable you'll see exactly the same PK fits in all turns out you could never have guessed that the Noland vinyl alcohol and say This Indiana Lansing PKA and PKC now so I hope you know that this is the most acidic of
the bunch the alcohol again that it's there's an electric really were just changing to more electoral negative ads legal carbon nitrogen oxygen so now we
get over here to this vine all this this being mean is the name of that functional group and the number of letters about 28 so panel and amino group of benzene ring was peaking about 28 so significantly easier to depot amino Wilpon benzene ring than just a simple amino group finally we get to a simple Alou like how easy is it to make an Alan I it's a billion times easier to the probe made a little at ages that his regular allocations ch like the 1 you have when you're hexane sold directly department your hex insolvent but with the right base you can mentally here Tom Howell position OK so we can make resonance worth more if I replaces CC double bond with the carbonyl group that out of you better residents stabilizer for any
kind on the other nite I expect you to know that care for the ALF positions Alpha to at the time and that's what this is now a decided that the PKK of acetone and I'm going to give you
a number of 20 which is a good sort of average value for Tito Alpha to Quito OK if we look at an a and M if you're interested in the peptide backbone in understanding how easy is it to images on a peptide backbone were approaching that it's not easy it's not impossible but there's a about 17 so a physiological pH of 7 now maybe 1 out of every 10 billion in my backbone just deep-rooted maybe that's not very many very low concentrations then finally come over here and replace this always cherish double bond in this final alcohol with common group and we have a carboxyl aghast that is about 5 4 carboxyl guests at doesn't matter if
it's 4 . 2 4 . 7 6 focus so you can see that it is even more of an
acidity effect with Kerviel groups than with simple CC double you should expected that the carbonyl groups a better resonance acceptors for the for and against and you need to know those numbers those the super common compounds of represent classes of compounds that keep going with train what the 2 of 4 of the people of the book so this is a concept that we've already talked about so this isn't in any numbers as you might think it is because look I'm giving you the same number I just gave you this number what is it for at 50 yes Saber hexane cycle hexane it's all pretty similar
,comma close enough so worried talk about 50 now what happens if we put a double bond in here it's not the same anymore overcome
along with a triple bond was in between these sort changing the hybridization of the Adam and so what happens to the acidity of the the going to become more acidic and it can be quite dramatic here the effects of again these are all ages there is no resonance anything going on and the higher character so if you look at the car then I am here the the copy and I'm that you would get by deeper admitting this is very nucleophilic very reactive and very unstable and in way it's unstable there's lots of P character here but as you reduce the peak character it becomes less
reactive the becomes more stable so fine when we get
down to sp hybridized carbon now is not all that P character that makes things so unstable and reactive there's plenty of sq 50 % as character here in this Connolly and that's what's accountable for this and what is the matter of 26 orders of magnitude is City Hall the same Adam carbon and we're just changing the hybridization so I hope by now in his class to respect the effects of urbanization and reactivity this gives you a sense of that affects the city OK let's keep going but if it did not differ from
what way this 1 really make
sense unless we walked back and we compared to the anyway over here as methyl Amin PK from methyl Amina dies of global Amina any any China regular Amin is about 36 and so what difference does it make to have a positive charge in the to not talking about a different compounds are not enemies I'm talking about the PKK of pneumonia mine is 1 of the most common mistakes is to confuse enemy for pneumonia I mean managers is a very hard to pull off you need lithium to deeper made a simple alkalinity this anything can be pretty well not anything but just about anything you did proving that the this is about 11 at the Lyceum side chain it is in a biological context and so what about probe alcohol well prepared all calls a little lower but approved made ETA units from out calls about minus to history
from Haiti there again the important point is the effective charge if we compare this 1 alcohol it's pretty
acidic but when you have a positive charge enough oxygen its various city says very easy to pull protons offer OCS Sonia minds oxygen to the bonds before marks on him OK so on water some were limited keep drawing some more species so I have an ammonium ion what about and many Miami so we talked about a many alliances reactive intermediates it's much easier to do nucleophilic attack to many mines and carbon heels the whole field but the whole field most of the fuel of organic catalysis is in many minds so he's a PK is on the order of about 5 2 others give you the number 5 and it's not right it's not the fact that there's just a simple isolated in the middle of the PTA for this they were too period Damien
it's 5 it's the same many on Damien it's about 5 billion book April made oxygen on the carbon
group now it's very very hard to prove that it's extremely hard if you want from the sometime about simple key terms if you wanna put us at Pro noticeable Peter what you see people doing as they say they had sulfuric acid a hydrochloric acid serious business assets minus 7 incredibly hard to prove nature carbon yield a simple Quito and that's put these in the context and I think I don't know why I have this year as the images you can seem like a know-it-all all but if if 16 isn't good enough for you and you somehow need to know exactly duplicated for water you can use 15 . 7 per and never had that BAT any better for me than 16 so if you want the main point years I wanna compare this hide roomier so we know a number for
them and that's minus to minus 1 . 7 so you remember
of somewhere here I noted this all these different that it if you have an approved mediator with 2 alkyl groups to minus 4 Hydro New minus minus 2 and a appropriated alcohol where there just 1 of those right in between ministers again I don't just wanna memorize kind of minus the an oxygen with 3 bonds and proton I'm sure that always do you right OK so next trend the last note to more trends to talk about and and these are the kinds
of numbers were you going to be in your morals examined and only at the board drawing something up and then suddenly hear this question from the back of your wedding the
PGA event a and turn the 4 year committee will look at each other like wonder why you didn't remember that that number so this isn't just for this class guys need to know these numbers in perpetuity 1 of the 2 . 4 minutes into the game so we obviously I'm talking about getting to a bigger and bigger Adams as we drop down from 2nd road to 3rd Road a 4th if it's true Adams and you'll see concomitant increase in acidity aqueous acidity there's a huge leap when we go from floor and this kind of corresponds to Leading Group ability a massively .period we go from fluoride according to chloride so HF is not like hydrochloric acid nothing like hydrochloric acid in terms of acidity where it has
a nucleophilic countersigned so HBO are then 1 it's very basic it's not that
different from each CIA In terms of acidity I can't think of many many cases where you get anything in terms of a city by switching from each HBO what you get is a more nucleophilic countless bromide and if you switch to a job I again it's if you just want a stronger acids you're not going to go grab a bottle Hydro I owe to Ghassan instead of HCl will go to sulfuric acid OK so finally were down 2 of them I think the last important comparison for this series and that would be by alcohol so alcohol is a peak at about 16 what happens when we draw from the 2nd row 0 wage to the 3rd World sh it's another PKK is about 11 and the peak is actually very considerably depending on what attached there so this is getting close to assisting side-chain you'll see numbers in the 9th sometimes for the Sistine
citing and protein PKO around 9 there's considerable variable variability when you start but polar groups nearby you'll see that PTA Grobbelaar but more
important point is it's it's 100 thousand times more acidic than a regular OH it is very easy to do file if you take any dilute put physiological pH there is a substantial concentrations of violating an iron in solution and their super nucleophilic filing yet the crappy going at the end of the OK so now polar affects you call these inductive effects of being that term some people would use physical number because we have so many tech reading intermediates they were interested in how easy is it to be prone made species like this where we have well whatever hall where we have more than 1 of Elektra negative advantageous attached to the
same carbon so you look at the PKK for this new kind of should expect that it's easier to be pro makers so
wage when there's an electromagnet that close by and what you don't know is how much easier the the nearby Elektra negative Adam should make it easier to the probe made that turned up the the is around 13 . 4 so that the the number itemize a thousand times more acidic than the animals at the point for really matters so it's easier you might have known that he might not have known how much the deal a major redraw redrawing a molecule that already drawn for you so what's the PGA this 1 5 yeah I'm trying their hand to and understand why I wrote these decimal places because that was gonna at 5 0 4 . 8 Britain care whether members will begin melody give you the number for OCT gas and what
happens if we put a fluorine atom here right now if I D probe make this this Proton there's no resonance structure I can
draw here in which the flooring is going to help them if there's any effective flooring it's kind like a through space interactions you know that the nucleus has more protons in the nucleus of Florence was more positive than all help stabilize negative charge way over there on the carboxyl late so that flooring automated easier to the probe made here and it does this much so schools from 4 . 8 to 2 . 7 it's 100 times more acidic to Ted that flooring close by like that and as you might guess to have 3 Florine very lecturer negative trade for acidic gasses is close to 0 the central-eastern Europe some 100 thousand times more acidic than a CD gasses when you see people use TFA trifle receiving guests as a capital case although the PKK I expect you to know you have to memorize those on the
translates that to those much easier I hope by knowing those PKA you'll always be able to rely on some trends that can extrapolate thank you for all of the 2 . 4 and
4 we are going to look at ,comma so I wanna look at some trends here for kill lithium and let me start off by by saying that it is not a bad conceptual tools we especially when your 1st starting off at this point I don't really expect you to make this jump on you when you 1st start off in organic chemistry you take your 1st year organic chemistry this starts to look very bizarre was like What's
this lithium carbonate Bond thing there and so most books encourage you to think of this as a methyl and
I trust me there is no methyl and I in a bottle of metal lithium is no free content on every single carbon is bound to at least 1 lithium and it actually formed egrets words bounded to insult people draw this because they just don't like that they don't like drawing a nucleophilic signal bond but there's nothing you're going to do with this lone pair but you could also do with Scotland the so just think of this calculation is about the same in terms of nuclear Felicity as you might consider that lone pair to be and the main point I wanna make here has to do with on the basis city and reactivity of the species I want to draw a trend here as we as we increase the size the data on the number of
carbons in each of the species it was the 1st go a
whole set of alkyl here and if you think about basis city what happens if you take us arranged it has met the lithium and he squirted into the air or into some water that's not a real show there's not a lot to see going on that I take a syringes TB lithium and I squirted into the air it will instantly burst into flames the 2nd the TV linking touches the water vapor in the air it's so aggressively Deep provides the water but the heat it generates ignites the solvent and causes a fire it's instant fire there's a huge difference in reactivity so if you look at it and salary phrases that this is reactivating its ability to be look at the reactivity of these more alkyl groups that you put on a on a carbon atom increases the solution phase activity and blind being so careful talking solution phase of activity because if you do calculations and this is why I'm just pointing out you have to be careful calculations gas phase calculations the dual calculation just a single word that the lithium molecule is drawn on the computer screen and you compare that there is what you would find or Ka-band irons this is the 1st of 4 this this was all yeah minutes amendments which this week instead of talking about this total alcohol sorry future environment sitting Of course so cheap you know all city which of these should make a more stable and 9 is the way you can think about this I supra open all persons ethanol because I think this will be more useful to you verses methanol if you look at the gas phase acidity of these it's the opposite it's the opposite of what you expect in terms of substitution it turns out that TB you know all is more acidic in the gas phase in the nicer probe all and that's more acidic than ethanol and that's more acidic than after it's the it's the reverse of what you see in solution phase TV Utah turned out to be more stable than oxide in the gas phase in general I feel like it pointed this out with with Candide In general when you look at the stability of larger molecules in the a gas phase by calculations they seem more stable and let me get your way of thinking about why is that when you do computer calculations on that larger things end up seeming more stable let me good and compare view these 2 types of molecules here I'll just start off with methanol firm about signing and I the thing that will stabilize either of these 2 molecules that the donation of field orbitals into unfilled orbitals so we're here I look at here's my nucleophilic wobble wanting to donate into well they can donated into the moral for the ch so I'm donating now Sigma started the CH bond if that's really true I would expect a little bit of nuclear publicity out of this if I'm really donating their bond and weakening and I would expect it to be slightly nucleophilic El Chile later some reactions were exactly that happened because that deletion is real but now I come over here that is larger molecules I donate with this and that makes this bond more nucleophilic and if I have another bond here I can take that those electrons and now that nucleophilic orbital condone it into this 1 and as I keep going the more bonds I have the more END bonding anti-war rules I have and the more empty rules I have more chance I have to donate fielded awards so in general when do gas phase calculations you'll see this this effect that larger on the canines are cobbled canteens look more stable but when you put them in solution you don't see you see almost no effect of that kind solvation becomes a more important issue will talk about solvation just move on and focus on mannequins so it's a little table here and I'm going to go and skip that what I wanna talk about is the effect of solvents what is what effect solvent have long on stuff like this 1 chemical reactivity and but it
was believed that the 2 of 2 of the 1st
things 4 the group also but the use of mom rate constant relative rates for a Finkelstein's reaction that's just a simple as into reaction and we displays a chloride tie-dyed and which is going to look at the effect of solvent on this SN 2 reactions that solvent effect this summer gave you a series of solvents I'll tell you what the dielectric constant police are and outside the relative rates not the absolute rate constants but the relative rate constants as I compare different solids I'm going to start off with water very powerful solvent nitro methane very powerful and and I'm methyl four-man medal just radium and finally acetone some
and moving to Greece here and I don't have numbers for hexane that is there would be no further down the list here that way what I would see the 2 from polar solvents to list polar solvents is an
increase in rate so I'm going to assign relative rate for a S into reactions in water is 1 that I simply switched to nitro methane it's 14 thousand times faster but you need to use this kind of thinking in the lab the center of reactions when you can make your Ph.D. 14 thousand times faster who wouldn't want to do that I go DMS nowadays 100 thousand times fast just by switching to a different I walked over to the shelf I grabbed a different bottles and how things are 100 thousand times
faster and acetone this
total for it's now 1 . 4 million times faster so instantly but whites faster than it otherwise these things were getting slower as we go to war polar solvent it's not all that good solid bold dielectric constant water is the most polar interest in terms of bulk dielectric constant but there is a trend here but you get to this stage and there's there's not an exact trend there's something else going on here especially when you look at this the nite from thing verses next summer water that's the biggest jump rising water such as Sockey reaction was set aside the solvent for this reaction it's not just polarity for the water is another reason why water on it is not good so
1st of all let me just of this of iodide is a minus charge either substrate here but chloride and there's
a there's a chronic advantage to having these things that closes a powerful positive charge and cotton the closer they get the more cool on law and I could calculate the more Cologne's tells me that it's energetically favorable to bring these closer together and if you have a dielectric here the larger the dielectric constant the bigger this is the last these charges can see each other dielectric high dielectric hides charges can't see each other when the dielectric on such part of this effect right but there's a 2nd major effect here is of dielectric is 1 and 1 origin of this differs from the Senate different but there's a 2nd effect and I'm going to drop picture of this iodide in 89 and the problem is when you products all of this is it's the product
solvents that really screw you on this it's not just this desire has not seen each other
affect the problem is this iodide is already and I don't know how to draw a little is guidelines iodide is already In a way kind of reacting because of hydrogen bonds with the sole we have solvents the product that form hydrogen bonds with nucleophilic species it's almost like it's already donating and went on to bonding orbital that's what the hydrogen bond is and with all these distractions around here you can imagine why it's not so easy for the side I did get interested in attacking anything so bonds distract nuclear files because because most nuclear files good ones or and ii having ionic character so this is
reason number to from the big difference so is that the charge screening effects of polar
solvents and there's this protocol solvent extraction effect OK it's harder to distract bigger Adams it's harder to get the hydrogen bonds organized around a big iodide mark the guy died in time but you'll find that you have smaller Adams it's very easy to form very tight hydrogen bonds from signaled look at the practical implication of that as we go to see the 2nd row and sulfur file it's harder to distract bigger Adams in it's easier to distract us smaller Adams but it would be 2 so you
put fluoride AI and cannot be a solution for this this is not
very nucleophilic in organic chemistry nobody uses or aqueous solutions of Florida and iron who would do that the hydrogen bonds between water and for I totally shut down the activity of the floor if you're interested in using fluoride is a nuclear power for example to attack silicon which you use is this the tech tributyl ammonium chloride I'm not going to draw the bureau groups that can form hydrogen bonds with the if you find hydrogen bonds of the floor it's over you shut down the nuclear Felicity so here's another sort of that I'm not sure if this is just a related
factoid if if you're into chemical biology we should keep this in mind for things like native chemical ligation of proteins yes Sistine files on proteins and means and
proteins and there are equilibrium city equilibrium between files and violating an alliance between the means ammonium most lighting citing the probe made in an aqueous solution most most violator also provided that a small amount of violating lines that are present in solutions in the aqueous solutions are sold nucleophilic that if you have a protein Europe if you equal amounts of Puyol enemies in a buffered solution :colon pH 7 doesn't matter what the pH and it is up to this was you'll
find files are more nucleophilic so you can see what the problem is if you're under acidic conditions almost all the means promulgated there's no longer on those things
that is nuclear files at least there's some violating I'm really try to go to more basic conditions of release you have an even playing field if you get a higher pH to try to get some your license I change the prorated will then you're going to do people need even more of the files 11 more the files around the the connectors in nuclear power so generally we have piles in opera solution expect them to be weighing more nucleophilic the license so unless you have 300 times moralizing sightings and by typically it's like 40 to 50 then we expect the final status of the system they were going to stop there without 1 last little piece of wood undercover winning now and get back on I've finished writing about half of those to proposals and Chris is going to give those back
Single electron transfer
Chemische Bindung
Hybridisierung <Chemie>
Elektron <Legierung>
Fülle <Speise>
Bukett <Wein>
Zulauf <Verfahrenstechnik>
Chemische Biologie
Induktiver Effekt
Organischer Halbleiter
Funktionelle Gruppe
Wässrige Lösung
Aktivierung <Physiologie>
Setzen <Verfahrenstechnik>
Gangart <Erzlagerstätte>
Braunes Fettgewebe
Spezies <Chemie>
Substrat <Chemie>
Amine <primär->
Organischer Halbleiter
Radioaktiver Stoff
Organischer Stoff
Chemische Forschung
Konkrement <Innere Medizin>
Chemische Verbindungen
Weiche Materie
Systemische Therapie <Pharmakologie>
Aktivität <Konzentration>
Schweflige Säure
Einsames Elektronenpaar
Potenz <Homöopathie>
Organischer Kationentransporter
Chemische Struktur
Chemischer Prozess


Formale Metadaten

Titel Lecture 14. Anions.
Serientitel Chem 201: Organic Reaction Mechanisms I
Teil 18
Anzahl der Teile 26
Autor Vranken, David Van
Lizenz CC-Namensnennung - Weitergabe unter gleichen Bedingungen 3.0 Unported:
Sie dürfen das Werk bzw. den Inhalt zu jedem legalen und nicht-kommerziellen Zweck nutzen, verändern und in unveränderter oder veränderter Form vervielfältigen, verbreiten und öffentlich zugänglich machen, sofern Sie den Namen des Autors/Rechteinhabers in der von ihm festgelegten Weise nennen und das Werk bzw. diesen Inhalt auch in veränderter Form nur unter den Bedingungen dieser Lizenz weitergeben.
DOI 10.5446/19231
Herausgeber University of California Irvine (UCI)
Erscheinungsjahr 2012
Sprache Englisch

Inhaltliche Metadaten

Fachgebiet Chemie
Abstract UCI Chem 201 Organic Reaction Mechanisms I (Fall 2012) Lec 14. Organic Reaction Mechanism -- Anions Instructor: David Van Vranken, Ph.D. Description: Advanced treatment of basic mechanistic principles of modern organic chemistry. Topics include molecular orbital theory, orbital symmetry control of organic reactions, aromaticity, carbonium ion chemistry, free radical chemistry, the chemistry of carbenes and carbanions, photochemistry, electrophilic substitutions, aromatic chemistry.

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