Lecture 07. Neighboring Groups


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Lecture 07. Neighboring Groups
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Vranken, David Van
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UCI Chem 201 Organic Reaction Mechanisms I (Fall 2012) Lec 07. Organic Reaction Mechanism -- Neighboring Groups 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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OK so there's an exam next week but it's going beyond Wednesday during the regular
class time on my office hours tomorrow have to be moved because of these kind of makeup lectures tomorrow on and there's no group meeting for my group this week in case you're interested in showing thank you for your interest I want to say something about this mechanism I think was there there who who asked about his son yesterday during our discussion section I looked up the mechanism for this post dilation and the presence of purity and they refer back to Paris to some earlier mechanistic papers and I think the mechanism does involve as there's somebody was Thank you for asking about that Gadahn realizes that even the president coming the mechanistic studies were for D but from what I can see looks very similar these go through an and Sile intermediates the leading group is not chloride in the catalyze reactions it's period in which doesn't change our energy diagrams but I learned something I'd never known total goes through in some animators a wheel us intermediate before and that's the more common conditions OK let's go ahead and continue where
we left off you and you would never have known there is no way for me to know that this I was asking you if right a plausible mechanism is no conceivable way you could know now
without kinetic studies don't know that you can known that for where this problem will from now on if I ask you about this mechanism in the presence appeared and that is all I want you to know that she would TVs to go through an entire species but there's no way you could known that hadn't focus only come back to this but we've been talking about cargo cat alliance and I want to talk about a love a little bit more about bonding insightful propane so we're continuing on with lecture 6 and we left off talking about this idea that that there's a lot of people character in order to adopt these very strange angles if I look at a cycle propane there's a significant amount of peak character this isn't as P-3 hybridized with arrest 3 hybridizing would imply that the 75 per cent as the character and his bond but there is more than 75 per cent p character so as a result of this very weird hybridization in the ring strain on these bonds inside of a cycle propane ring have more people character and are therefore more nucleophilic than your average run-of-the-mill carbon-carbon bond as as a consequence of year you if this carbon atom is using more P character to make this bond that has left the character to make the bonds outside of the ring so as a consequence of that these bonds out here have less character in a normal ch and as a consequence there less nucleophilic so that's what's weird about the hybridization of the carbon atoms and we can put some numbers on that for example if I compare on of a cycle pro-poor ,comma BNI and with just a regular run-of-the-mill Malkiel ,comma outright put something in untrained bringing here so we can compare if I compare the basis city of this Caribbean island with the bassist city of Aqaba 9 on a cycle hexane ring which is normal sp 3 what you'll find is that that it is that this long pair is tender the 5th unless basis right that the bonds
on the outside of the ring have unless he character these bonds alone pairs of things they're sticking outside the ring have less speed character those bonds alone pairs are
less nucleophilic and unless basic than a regular bond by a lot 100 thousand is a lot the case was that some more numbers on this idea that bonding and cycle propane can change nuclear Felicity of according to the and so I want to introduce you to a new term called cyclo pro Bill carbine e-mails that just means of a carbon atom attached to a cyclo propane and specifically were interested in cargo can irons that have cycle dangling off the loans and so let's let's see what happens in reactions that would make those kinds of hobble Caroline's I want to
consider as anyone 1 reactions of some top oscillates were tossed elite is the leading group and if we just think
about that the relative rates here on I'll give you some relative rates relative to adjust their full toss a lake which you might expect is a pretty bad ionization reaction to give a primary Koble can before she can accelerate that by having a pie system next door we apply for wise this fast it's fast because the price system is donating unity and declining moral and helping to push out that leading group or if you wanted to use the Hammond postulated talk about herbal Kanye instability could say Well the Carbol can iron is more stable than it looks like the transition state the bottom line is that by systems next door you should know that bends Ilic cobbled headlines or stabilizing the benzoate leaving groups leave faster and what I wanted was I want to compare this with the system where there the strained bonds next door
not upon system but just strained bond in that cycle probing rings so here the bond that's sort of can potentially overlap in the right confirmation with the
antibody model this is 120 thousand times faster than just a primary can on all 3 of these are primary Korbel Caroline's in theory we get a sense that you may have thought that benzene rings and simple double bonds were all that for making Alacano lines and that'll Bengal cat lines with if this this is kind of pathetic looking in comparison cycle propane sisters gives you a sense for how Austin instability on on-site willful vinyl Caroline's so it's going just draw out those Caroline's you would be 1 of cycle pourable carbonic cat and I'll compare that to something that you might think is a great can iron output benzene ring on a mecarbil Caroline then allowed another benzene ring on a
cargo Caroline and analyze 3rd benzene ring on the cobbled guidelines called the Triangle Caroline found on
the phone this is still cost stable this primary Koble characters still more stable than it try till cat I just to give you a sense for yes you can the U.S. on I don't know that these are easier to attack so there's a there's other sites to attack the kinetically not reversible where straddle Candide edition is reversible OK so cycle bubble carbonyl accountant Super Duper stabilize look for reactions that make cycle probable carbine all kinds because those will be fast reactions so I want to talk about the importance of the orientation of those orbital stands I'm going to struggle here to try to draw out what kinds of orientations are good for stabilizing
so let me try to draw the Carbol Caroline I'm with an NTP orbital here and the single
best orientation for that cycle propane rain would have each of these bonds sort of aligned so that they could both simultaneously donated to 1 lobe of the people that's the optimal confirmation of a cycle pourable ,comma vinyl cat eyes or sometimes you can tilt the soldiers 1 of them is perfectly aligned that's also a good orientation but in contrast if he spins around the wrong way you'll get completely opposite effects so my orbital there's my cobble Caroline I spin that surrounds the this ch bond up here it's not a good three-dimensional drawings so that this besieged bond appears on client that's lousy that's a bad orientation for a cycle propane so you really want to have these out either 1 of these bonds ideally perfectly aligned perfectly parallel to that NTP well that's the ideal line let me
on that should say what cruise a going to write something
that I was an interim there 51 arrived PAS has never mind the you wanna write something else that it's that focus a little compared to different systems I wanna look at a constrained system because they think maybe it'll be easier maybe of obviously these effects you can start off Monday drawing adamantine ring system on and you can start up by drawing a chair conformation and I just wanna be able see exactly where that energy Bonnie Moore believes there's an empty word all there on time so why is it 1 of the things that make this possible to finalize this tussling leaving group there's an empty will Cigna star orbital here and there are things in this Adam mental structure their donating that anti-war also specifically
this axial bond over here and then won in back are aligned with that empty orbital and our overlapping in
space with that the world the donating electron so it's the donation from the sigma bond into this indie period cleaner into the Sigma star warble of the St. plainer ,comma not seen 1 that's what makes it possible to find myself this tussling group if you put it you construct a compound that has a cycle propane ring right here that becomes way faster it strains the bonds it strains this bond so that this carbon animosities more P. character and when there's more P character in this bond when you have that cycle probing ring their it's tend to the 9 faster so a billion times faster with the cycle propane there because that's a bond that's perfectly aligned here also straining this bond down here but that doesn't do you any good it's not overlapping with the antibody model so let's
take a look at a system that's not so well designed by me draw another Adams up another
at a mental system also start with a chair but I'm going to put the top-selling leaving at different positions on all draw this with my axial bonds going down like this and so now I have the capacity potentially to make a tertiary couple can I'm with that but take a look at the bonds the oriented with debt into bonds that will hear the orbital on the back side of that tussling that's my Sigma star orbital and these bonds over here aligned there's a bond that's aligned with any undermining bonding orbital that a bond line here a bond that's a line there in the period planar the tussling Leading Group on if I if I make the mistake of putting the cycle propane over here that doesn't strain his mind this is now like 1 of the bonds it on the outside of the
cycle propane rank this is now a thousand times slower and I don't have room
here but you would write with I'll just write with cycle program with CPC supercycle probing that slows it down so you have to be careful how the cycle programs are oriented ,comma relative to that leading group it's not simply sufficient to be next to the leading group you have to worry about the orientation of those bonds industry including OK so I want to compare DNA and the unlimited give your residence picture from what's going on and it's going to be very strange-looking on the when we try to think about how relied for all this intermediate weather cycle proclaims donating it into and NTP warble
whom what can I do that tho
I mean this is the shape and other words like when I drop couple can I'm I don't I don't like him drop but the actual shape of of an NDP orbital it looks like a speed record and I think it's a never know how to draw this kind of bothers me is Robin that way so if you look at the shape of an NDP orbital and draw sphere around this carbon atoms and actually take half a sphere Peron atmosphere up there that's actual shape of the hospital look anything whatsoever like this the fossils whoever invented can draw in the 19 mid-1980's through ovals like this and Stew mandated rather more like a half-page this this is just 1 empty fuel at its
space like this I sometimes don't draw the phasing in just because yeah so if I draw the extra parts of this and Sigma
Stone looks like this if I include the phasing attached here not hatched years no interaction and hatched here again so you register or the big part yes and yes sometimes although like this but when I prefer to draw like that actually OK so empty so some residents picture for a cycle probable carbonyl can I that draw cycle operable carbonyl Caroline and I want to think about how I represent this said there's really no perfect representation if I really believe that this bond is donating into DP orbital like this for 100 resonance depiction that looks like that is richer residents
depiction will look like it'll look like this if I really believe this bond is donating into that the marauder replied character here in cycle properly
of in that cycle pourable carbonyl can I'm there's another resident structure I can control as well it if I really believe that this to describe this carbon-carbon bond is donating into that on empty into empty curable maybe I should think about this carbon carbon Monet's shifting all over there's a different resonance structure I could draw the trial this bond away from this dotted carbon here and and I leave the cargo can I that center these are all valid resident structures for cycle pro vinyl Qatar as hard is it is it is to think about three-dimensional what you find just just to convince you that this is that the residents structures the valid ways to think about a cycle probable carbonyl can I'm if you make the cycle
bubble carbonyl Caroline's so if you take an amino methyl cycle propane and you treat with nitrates acid generally dies owning leading groups those leaving water what you get is the
distribution of products on that contains this substitution product if you get this substitution product when you get this substitution productivity all 3 of those substitution products they're all equal ratios that doesn't matter that much you get the same distribution of products it the same products if you start with this Leading Group on a site on us cycle butane rank so you're you're sort of entering the same kind of Cobble Caroline and if you start with the cycle butane talking so if you whenever you see the possibility to die a nice things off of cycle Beutel there actually a little bit slower but they end up giving you with this very similar kind of
Cobble can give you the same type of trouble and that looks like a cycle operable OK so cycle
propane Bonda magnificently strained to the Super nucleophilic yes we know that to the arm that was supposed to be yeah so when you have this cycle probing here it's now a thousand times slower and if you make it without the cycle propane it that's relative to the 1 that has no cycle probing because this bond has less the character it's bonds that this bond is outside the cycle preparing those bond the out sticking off the edges of the cycle probing those bonds have less P character and a less nucleophilic it's the bonds within the ring that have more P character and these aren't overlapping inspections that and warble that we have in this
case this is within the range of this this EC bodies within the ring so when you make when you synthesize this directive
that as a seedy near this ECU bond is within the ring and so Silver nucleophilic screening not nucleophilic won by having by by having this this carbon-carbon bond be part of a three-member going OK so it's not about a different type of nucleophilic bond so everywhere look for Cycle propane and leading groups next to them better than a TB cars that were better than us up at trial that I just have 1 cycle propane bond nearby the onto draw I want to remind you of the effects of making bonds longer what happens when I take a bond and I make it longer and I just wanna compare the canonical molecular orbitals for bonds where for example I simply make things longer so it could stir up I think about a carbon-carbon bonds and the Soviet TV will reappear I want to be a 2nd keeping similar someone I think about the orbital for that ponders a Sigma CC ward for this field and there is less of a stigma star war but all equally hiring energy for that bond and so what happens if I if I dropped from carbon down to the next role the periodic table from carbon to silicon what happens is the bond gets longer so we try to emphasize that in some ridiculous way like this is you can say so and you can have as I H 3 easily so they owned the values reported for trend but the prediction is that this find is longer it's less stable there's less warble overlap less effective orbital overlap the bond is less stable that means it's hiring energy and that means that the
distinguished orbital lower energy that's not so important
what's important is that this is now hiring energy and friend dropped it 1 more bomb on that I drop further below the Periodic Table 2 10 holidaymakers even better you know I don't know if that looks longer then your expectation is whatever silicon does team can do better anything silicon is known to do Coddington bonded better the more nucleophilic stabilize cobble can more than faced more toxic gas the stink more come they always do things sort of one-upping consul command your prediction is carbon silicon ones should be super nucleophilic longer bonds are on more nucleophilic so let's see the the implications of that
stabilizing adjacent cargo can the latest in a so I'm
going to draw a simple comparison so but we talked about before the effect of all of these ch bonds on a T Beutel Koble Caroline it's CCH finds that a stabilizing at TV will cobble can I know if you compare that to TV cobble cabinet there is just 1 single Carbon Silicon my next door to trainable silo everything else the saying but that single Carbon Silicon Valley there were detrimental style group this becomes more stable by 38 K from all so how many times more stable is
this when it has this carbon silicon bond at the beta position we call this a beta silo cat eyes 2 2
words beta site will count how many times more stable is that any whatever that is divided by 1 . 4 it's tender that power tho it's something like 20 some 10 the twentysomething Luna's or something like that to a huge amount more stable tended 20 something more stable the fact if you convert this factors attended some massive increase instability so look for reactions that can generate data silo cobble no I'll tell you is it is actually not very common to generate Vegas-style cobble Caroline's through S N 1 type ionization reactions but as we go through this course what you're going to find is later on and you're going to see
a million reactions that generate beta cell Cobble can like this and will get
to this this is the way you most commonly see beta so troubled Caroline's formed in organic synthesis every time you see analysis later vinyl sigh Lane you need to be thinking about how smoking hot maybe I should say highlighted how incredibly stabilized on this cargo Caroline will be that's not just a regular double bond that double bond can make a big missile coveralls so look for Lilic silence look for a little extending look for home any chance you have to put on this long Carbon Silicon bond next to a cobbled can OK so this is not just the carbon group it's not just carbon silicon tin any longer bond is more nucleophilic so that means
every single time you've seen a metal it doesn't matter whether it's palladium or cobalt or
rhodium every single time you've seen a metal that has a chance to have a beta cobble Caroline that's going to be a super stabilized ,comma cattle sold draw this there so metal cargo can alliance that was is 1st stabilized so carbon bonds are longer and and the very nucleophilic yet and I get along with all the history of the bond is longer so if I have a longer bonds it's hiring it's less stable attire and energy and the Tianhe energies more nucleophilic the Piper
conjugation means that the bond is donating advantage that is a different word
for what we're supposed to talk about the wife of honor I have to look at that year's light complex so far silicon here and carbon here I still have a longer bonds the problem is that this is no farther away from the Groveoak and I can remember I've looked at before now I can remember it's nothing special and I can't think of anybody puts leading groups of silicon ingots a beneficial effect that other that so my main tuition is that no it's not that the the fact that this bond is longer doesn't make up for the fact that this bond is longer in his father it to donate way a longer distance over to the empty pure OK so some bonds can be very nucleophilic and can very much stabilize Koble comments that's the whole point of that that lectures and Alex go 1 by 2 the onto a new
topic or maybe it's the same topic which has a thousand
different way condoning it into an empty words and then you know it's not like every reaction goes to cobble Caroline's my hope is that we'll be able to take these ideas of long bonds strained bonds those kinds of ideas and applied and other kinds of empty orbital like star and singer star when we get there it is so wanted some other types of groups that you can have next door to leading groups and that's the main idea here and I wanna
start up by talking about a topic that we've already talked about and that is what about federal Adams
this is this is so what I want to do that when you consider the ionization of this leading group in order to give a Carvel Qatar and so yeah others there's of oxygen lone pair up on top but that's OK don't worry about that is the main point I wanna make is what's the effect of having another federal Adam right here and let's put this in the context of the DNA and RNA for this could be NAD +plus it's an enzyme called factor so what would you predict about the ability to this for this based in DNA RNA
Purina pretending to act as a leading group how easy this is a source of mutations in DNA what's
the effect of having a hydroxyl disappear does that make it faster doesn't make it work always said is that these lone pairs are never nucleophilic enough to bend over and push out the leading group the only effective having an Alcock CIA hydroxy group next door here is that this slows down this is an electoral negative Adam and makes it harder for you to form an OC union minor Koble can at center to center being slower than it's about 150 times slower -minus not a factor of 10 the 9 attended the 20 but that's still significant it's slower to deep urinate or lose the free the purine based on is from DNA when nature made tonight Adenan manically Otago factors where there's this Leading Group built this is
the on this is the base that's attached to any D-plus
of nature made it with this extra hydroxyl group .period didn't use a DNA fragment to make that that slows down the loss of that group not ever do you want the group to act as a leading group for further coal factor type reactions so on it and that's the the effect of having this hydroxyl it slows down the loss of the season rupiah so oxygen is not what you want to have at this and this and all opposition this and all cheerleading group if you want to have a fast ionization reactions on but that's only for oxygen but see what happens when we switched to nitrogen and the from the kills me this is a clinically used anticancer drug sold as master agenda please get off your ass and get out of here and go invent better drug than this it's a very toxic you can design something better than this confirmed
positive of that the whole idea behind seating cancer-drug is this this nitrogen
is not oxygen nitrogen long bears are dramatically more nucleophilic than oxygen on pairs and if you have a nitrogen and I mean that's visible cheerleading group that can help push up and it's not that nitrogen ,comma bond it's the lone pairs that helped to push out that Leading Group and so what this does is it makes a strained Damien so it's not an easy redeemed its it's a it's got too many bonds equality 0 and what kind of like ammonium Acehnese Eugenia mine and is not as strange and that strain allows it to be opened up relatively quickly by nuclear files like DNA hazardous leads to not just a single alkylation event was a very easily
repaired bicycles for what it does it cross links because now after this opens up you can imagine the same thing happening on the other side and those types of
cross links are virtually when we draw the DNA appear because I've run out of room so now the same thing could happen on the other side and you can cross another strand and those types of problems DNA are virtually and repairable do you themselves kill themselves they undergo apoptosis if that's a problem so nitrogen lone pairs yes they can participate in what we call neighboring group participation for oxygen isn't helping the oxygen long pairs lessened gleeful you couldn't have known there would be that distinction you couldn't have known that the difference in nuclear philosphy for nitrogen Perez enough to allow it to make those strained rings so fond if you're looking for evidence that these things are more evidence that these kinds of Azeri Dania are important intermediates if you size this kind of
borrower means and there's nothing special about the chloride would be the same if you made the toss late and you do substitution reactions with this Maria of
some sort of a nucleophile this is 1 of the products that you get to me Drossin stereo chemistry heroes something see what's happening it'll be completely inexplicable to you why you would get a six-member bring product unless you know about this a 0 opined formation so you can tell what's happening here what's happening is that this lone pair is helping push that out to make a three-member grain and then the nucleophile opens up on the other side so in fact get a mixture of both substitution products from this time and I'm not going to draw the intermediate I'll leave that to you to draw that the three-member during a 0 Denny minds in that case I know of
oxygen is less oxygen
longer perilous less nucleophilic unless they think to just to put some it up I'll bring this back to that turn a city and basis city money take this sort of just below that of the Soviet look at the relative basis cities of the longer you can go to a peak table lookup approval needed oxygen verses approved made a and the PTA's will tell you the relative basis city of those long pairs and so in terms of relative basis at the peak a prime became prime means by but a proton on there for this on you about minus 2 0 to minus 4 depending on whether this is our age for pneumonia mind it's 10 that's the PKK from lysine side chain a triumphal ammonium those sorts of things 12 orders of magnitude different in basis city this is 12 orders of magnitude more basic and approximately that much more nucleophilic again
all because oxygen more electoral negative the nitrogen so oxygen lecturer negative there's more
protons in the nucleus and because this is more a lecturer negative if you try to make a cobbled can and when there's an electromagnet negative Adam here it kills you it's really bad this is flooring really destabilizes the couple can and have an electric negative and I'm here yeah I know about it is that the have intellectual negative so you have an elected negative Adam here the lone pairs on helping you all you get is the battle lecturer negativity of oxygen it's destabilizing the problem that I don't know yes really need to get it sanity to the leading group OK so was only when it is most urgent thing came
from bomber came from people trying to kill each other the and it would be the and if
you win in the back so the the casualties due to and chemical warfare agents in World War Two me and here is you are 1 of the principal chemical agents that they were lobbing back and forth at each other during which so I will work once during World War One and this is not a nitrogen mustard and was a sulfur mustard I'm so when you hear people talk about it chemical warfare and mustards they're referring to the sulfur compound and it turns out that site where it is sold for fitting it is that like oxygen and don't push out leaving groups or is it more like nitrogen also offers in the same role with oxygen is called a Chalco 4 because these long longhairs because the sulfurous the bond as long as the lone pairs heard far bigger on everything is bigger bombs a longer along there's a bigger the longer the more nucleophilic and sulfur and so it turns out in this case you do get neighboring the participation for sulfur for selenium once you drop below that 2nd World also sulfur is not as electoral negative as oxygen so you you suffer less of a penalty in ionization reactions but when you pop this thing off unit generating this is what looks like a weird species here this is not what it looks kind of like in a park side but it's not Parkside week it if this were neutral we call this and that the sulfide but it's not even
a happy sulfide there's a positive charge here we call this an sold phony Miami you don't call Promina Parkside and happy the talks
only in the note Yukon it it's like and it's the name comes from something like a pox on it's a soulful line again and in the presence of water in your lungs and unfortunately this opens this up and I watch all the steps but the important point is that star-crossed proteins mainly it's too fast this is too fast to happen wait around for DNA starts to generate 2 moles of each seal gas of Ferrari 1 of these of the everyone of these molecules against your body and HCl cause edema parliament stars Bush skin very bad stuff OK so sulfur is it's more like nitrogen for different reasons on the sulfur lone pairs are more nucleophilic an oxygen long pairs and on the end of this and that and this
is the 1st time all the people in the why that slow yes Dear just very hard for nuclear balls to attack a tertiary centers so keep that in mind and put off by a week there right next door to the Toseland we can see the lone pairs are ready to help push out just like I told you the lone pairs are ready to help push up this time oscillate fileted the products you get out of this reaction you get 2 different products if you use
ammonia as your nuclear file for the time when you get those products in
a four-to-one ratio to let me go and drop that at the Seoul phony amine intermediate did you generate so the reaction starts off Armed with this ionization reaction the sulfur lone pairs are pushing out the leading group so you get this happy soulfully mind and now if you're using a mean as the nuclear problem this case ammonia that ammonia has 2 choices the ammonia can attack over here at the primary position an attack at the more substituted position and you can tell from the products that the dominant mode of attack is for the army to attack at the war substituted position that's the general nuclear
files attack at the more substituted position when you have positively charged three-member during only
so you learn some sort of a rule in some organic chemistry that all yours attacked more quickly on innocent you reactions that primarily serves the positions that long and it's wrong in this case a three-member during so let's be clear about where this is true self in Indiana pots I like this it's faster to attack at the primary position but if you probably made it through it prefers to attack at the tertiary position yes it is and that is what we know he would still attack but it doesn't go through Aqaba so if you make an up on a Quaternary
ammonium notice that there is a positive charge year nuclear files preferred to attack at the tertiary position if you
have that Bissell phoneme ion and again it doesn't matter whether it's Quaternary or you know whether it's secondary or tertiary nuclear files attack at the more substituted positions idea of mercury mind we don't cover epoxy Mercury Asian reactions anymore and we used to cover those in himself more organic chemistry Mercury's toxic these will prefer to attack yours get attacked what what we refer to as mark Connor cough edition of the nuclear file to the church's position its opposite if you don't have the positive charge the effect of this is that you're really the maybe I oughta be exaggerating the structures in a way that helps you to remember this but this bond is just a lot longer than he had his own and it's already pretty broken before the nuclear file comes in so yes it is daraclean Kumba detected that tertiary position that the bombers already partially broken in all these 3 types
of structures on so this is the general so it's only minutes and neutral three-member bring that to attack at the less substituted position in 1 of the more
likely meaning that what if you had something like this and it was maybe over here the variability in and lend money try to make equality should put another group on the sites another post-secondary by then I predicted attack you're faster than the United States England it on did you know meeting as afterward Sanath entrances so I'm not getting it but you can ask me
afterward OK let's look at some other day I just finished covering about 2 examples make strange three-member brings and money step away from that because it's not like every neighboring group has to make a strange three-member terrain is
kind of surprising isn't it that you get neighboring groups that will be readily form three-member during intermediate 1 thing I want to urge you not to do and I'm going to do this and you just have to to remind me that they stop doing that on is I want to stop calling these are if you're about to do not call this innocent you reaction so he do some substitution of this by some nucleophile that's not innocent to by definition into means that the transition state involves both nucleophile and electric power they have to collide 10 times constellation of nuclear power means 10 times higher reaction that's the definition of to rate
equals the rate constant times concentration of acts times concentration of nuclear fall by definition this
is lesson 1 reaction so I think I don't have an alternative to this as in 1 s into language and nomenclature that we use but this is the whole lesson 1 into system breaks down when you want to describe this as not rest until it's actually innocent 1 reaction you know it involves a concerted displacement OK let's take 1 more than 1 more example of neighboring group participation that involves the lone pairs of the 2 peoples we will it was the 1st time in the Crimea 2 different substrates that toss later here and in each case told Reuters and ascertain group in nearby and of course oxygen as lecturer negative so maybe that's not so good but you can get a beneficial effect out of this any matters scary chemically the way that neighboring group is disposed so if I look at the relative rates for ionization for popping out of this tussle a group what you'd find if you measured the rate at which tussling leaves from these you'd find this other Isamova over here the NTI isomer is 600 times faster that 600 times faster that summer and that you can kind of guess the reasons why a minister up by drawing the Senate confirmation that can help you see what's going on in this chair can flip back and forth between different share type confirmations and will eventually reach a confirmation in which this time oscillate is oriented where this carbon alone pair can help push that out and I'm like all those other examples that I showed you if you think all that this doesn't look so good there's those that sell bonds but this rating has none of that strain of the three-member rings so maybe it has to be generate a small amount of this axial confirmation but now there's nothing stopping this there's no range-trading stopping this from cycle icing around to give and I'm going to all this with a flat structure and to OCS only minor intermediate so here's the intermediate that you'd get in
this reaction would now have the and is not realizing that I think I'm behind the timber of this old style and if you want you can make this Gaston
-dash emboldened hatched sorry about that but I didn't mean to do that so you get this intermediate now essentially you could draw an equivalent resonance structure with a double bond here so that's not Sonia mind with the bonds to oxygen this particular resonance structure and so now the nuclear in fact an attack by either side of this you'll see 50 per cent the attack occurring here in the drawer the other residents structure you can see why the other 50 per cent of the attack occurs down here at the bottom on unseeded both Indian tumors out of this so and ultimately a land of getting if you're doing a reaction in a seedy gas at Sony write this down with all right Bassett Telesis to indicate that my nucleophile here is acetate so in the end you'd end up with half of your acetate and I'm attacking here have your acetate and packing their generous receiving next year even if he started with 1 with a single and anti-America substrate OK so that's neighboring the participation by long periods but we're going to have to stop there and when we come back to work for many consider a
little bit more what it's like to have double bonds ,comma New year leading groups not directly directly adjacent weight workable can but some are just a little bit farther away now
double bonds pulleys some oral health to help push out leaving groups and of course the answer is yes can we'll see how much that could be worth it in terms of rate acceleration


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