nm0691: right when i [1.0] finally find [1.8] the relevant slides [0.2] we can 
get going [4.2] okay er [1.3] we were talking are we [1.5] sort of [0.2] er the 
[1.6] this lecture's being recorded for [0.2] the benefit of mankind [0.4] so 
[0.2] er [0.7] that's why there's an additional member of the audience [0.5] 
the [3.0] form round that's being passed around you should sign which will tell 
us [0.3] which members of the audience that should be here aren't here [0.5] er 
[1.2] was everyone here b-, [0.4] present when i [1.0] talked about the exam 
structure [1.5] i think most of you were if anyone ha-, wasn't present when i 
discussed the exam structure [0.3] can you see me afterwards [0.3] 'cause we 
haven't got a huge amount of time now [0.4] er [4.1] right [10.2] let me just 
[5.4] recap [0.2] we were talking about rearrangements [0.6] the migrating 
group going trans and it occurred to me that you hadn't followed it [0.4] 
wholly [0.4] er [1.2] wholly [0.4] understood what i was saying [0.5] let's 
look at this [1.0] because this is in your tutorial [0.9] okay [laughter] [6.0] 
cyclohexanol [1.1] if you treat it with [0.2] er in in in acid conditions [2.0] 
dehydrating conditions [0.4] you [2.6] can get [5.5] you 
will get the formation of a carbocathion [0.6] but [0.2] in actual fact [14.1] 
what reacts in cyclohexanol [0.2] in acidic solution [0.3] is [0.4] the [1.5] 
two groups that are trans antiperiplanar to each other [2.3] so the O-H has got 
to be pointing down the hydrogen's got to be pointing up [0.5] and [0.2] it 
does that and you get an elimination reaction [8.9] right [0.5] so [0.4] 
elimination requires you remember from [0.3] Dr namex's course or perhaps you 
don't [1.0] [laughter] er [0.5] there's [0.5] was [0.8] elimination [0.4] the 
groups have to be trans antiperiplanar [0.8] now [1.3] in the case of this 
weird and wonderful decalin system that i showed you [0.5] er [16.8] we 
protonate that [0.7] now i'm going to save time drawing it [1.8] i'm going to 
protonate it up there [3.8] now [0.2] can we get elimination [2.3] well the 
answer is no because [0.2] n-, we need to have a hydrogen [1.1] obviously we're 
going to eliminate H-two-O [0.6] we need to have a hydrogen in an 
antiperiplanar [0.2] arrangement [0.7] and that means that [0.7] that in this 
case [0.6] the ring 
can't flip [0.4] as you probably recall [0.7] decalin rings [0.7] fused rings 
in general have very very little [0.3] conformational freedom [0.3] so this 
ring is fixed [0.2] and it means it can't flip such that the O-H is pointing 
down in an axial position [0.7] and so in this case [0.2] you don't get 
elimination [0.3] what you get rather is a migration [1.0] so you form a cation 
[0.2] and you get a group [0.2] migrating [0.3] this group here [1.2] for 
example [0.2] will migrate [1.6] and the O-H will fall off [0.8] in the normal 
way [0.2] and [16.9] and the product we eventually get is the eliminated 
product [0.3] but now it's in actual fact [7.0] that compound [4.3] it seems a 
bit mysterious really but it's not [0.6] all it all that we're saying is that 
the groups have to be [0.4] trans antiperiplanar [0.2] to each other [0.4] in 
order to [0.5] be able to [0.2] er [0.4] migrate [5.2] okay [1.8] in general 
rearrangements really come into their own in cyclic systems [0.4] the cyclic 
systems are where you can get some good transformations [0.3] in particular [0.
3] er [0.3] you can form [0.2] five and six member rings and 
you remember last week we were discussing the pinacol arrangement [0.6] and we 
had [0.2] two options with a [0.2] with a one-two-cyclohexanediol [2.2] 
depending on the [0.3] er [0.2] configuration of the diol at the start whether 
the O-Hs were trans or cis [35.7] now [0.4] this is a good one [0.4] here [0.7] 
and this is also [0.2] in your tutorial [1.3] it's also [0.2] if [0.6] i don't 
normally recommend colleagues' books only [0.2] only my own should i happen to 
have one [0.3] er [laughter] [0.5] but [0.3] Professor namex's little [0.8] 
monogram on [0.2] polar rearrangements [0.3] has all the answers in [0.2] 
because that's what i used to write the course before he came here [0.3] even 
[0.5] and so [0.2] er [0.5] it will have all the answers in [0.8] it's [0.6] 
probably not necessary to buy these things we did arrange to have all these [0.
4] Oxford primers in the library in the short loan collection [0.5] so if you 
go over there you should be able to get hold of it [1.3] but [0.3] this is er 
[0.4] a particularly good one because it b-, both of them give the same product 
[4.2] oh-oh [0.2] which i've have 
to draw out properly [8.9] this spirocyclic compound [17.7] perhaps i'll put in 
the er [0.5] the wedge line [0.4] here [3.5] from the hash line at the back [0.
6] just to emphasize you see these are spiro compounds [0.2] those [0.3] spiro 
systems are are not necessarily very easy [0.2] to form [19.2] but you often 
find [0.5] that rearrangements can give you that sort of [0.2] unusual [0.4] er 
[0.2] cyclic arrangement [1.1] the other [0.2] the other type of reaction where 
you get some really strange [0.3] cyclic compounds are [0.3] photochemical 
reactions [0.7] but [0.3] it's outside of the scope [0.9] of this [0.6] series 
of lectures to talk about that [9.3] now [1.2] i'm going to put up [3.7] some 
alternatives here i'll just er [0.8] try and [4.6] because i er [2.2] i'll have 
to shut the curtains i think [3.1] because i'm so kind to you and gave you the 
printed handout you don't need to copy this down [1.4] it's also on the web [0.
2] and some of that's in colour [0.4] and that was brought to my attention 
yesterday that i'd [0.3] i'd write on this sheet things are blue [0.2] 
when of course they're black and white [0.5] but i couldn't afford colour 
photocopying to [0.4] give to you all [0.7] here we have some variations on a 
theme as it were [5.4] and these are [0.2] all [1.4] what i would classify as 
semi-pinacol rearrangements [16.6] right [0.2] the driving force is always [0.
2] formation of a carbocation [0.3] with a positive charge [0.2] adjacent to 
the lone pair on the oxygens [0.7] that's what causes u-, us to get this 
pinacol arrangement [1.8] that's what's happening here indeed [0.2] one of 
those O-Hs is being lost [0.2] and then [0.2] a group is migrating [1.3] i 
haven't put up the mechanism because i'm sure [0.2] you will all be capable of 
doing that yourself now [2.7] i hope so anyway [0.6] right [2.0] these are [1.
3] diols [0.2] and and the er the classic pinacol arrangement is [0.2] the 
rearrangement of a one-two-diol [1.7] we can generate w-, there's a ready 
source of diols [0.2] we can generate [0.3] diols from [0.3] v-, via the 
dimerization of [0.4] er [0.8] ketones [1.2] dimerization of ketones [0.2] 
using [0.2] mediated by [0.2] n-, normally magnesium [0.4] magnesium and 
mercury or something 
like that [0.4] would be [0.2] suitable [0.2] but we can also generate diols 
from [0.2] alkene plus osmium tetroxide [0.5] should we so desire [0.2] and 
that that way we can actually get [0.8] a f-, er a handle on some unsymmetric 
[1.0] diols [1.5] there are [1.9] other ways of producing diols of course [1.2] 
osmium tetroxide always in cyclic systems gives you cis [0.6] diols if you want 
trans diols [0.3] then [0.9] you can s-, [0.3] also generate them from [0.2] 
you can generate them from alkenes by [1.7] epoxidization followed by [0.4] er 
nucleophilic attack and ring opening with base [1.3] so we we got a handle on 
diols there's there's plenty of them around [0.2] so synthetically this has got 
[0.6] enormous utility [2.2] 
if you want to make that [0.7] type of compound [1.9] and [0.2] and [0.4] 
really the gist of what i'm i'm trying to get across [0.2] is that [0.8] in a-, 
in aliphatic systems i mean [0.2] that's all very well ver-, very interesting 
[0.2] but in cyclic systems you can often use this to change [0.2] the way in 
which the ring looks [1.7] now [0.4] we're not restricted to diols [1.7] we are 
[0.5] we have this range of other systems [0.2] which generate [0.5] in the 
last case a similar [0.2] in the other cases the same [0.3] carbocation 
intermediate [0.5] here [1.8] so [1.8] where we have an amine there [1.3] we [0.
6] treat with nitrous acid [0.4] and we diazotize [0.2] we then lose the 
nitrogen [0.2] as gas [0.3] it's entropically driven [0.5] it's a very rapid 
reaction you remember [0.6] in in [0.5] aliphatic systems at least [0.2] so we 
lose the nitrogen [0.5] and [0.7] we [0.7] generate [0.2] the carbocation [1.0] 
similarly [0.2] we can ring open an epoxide [0.4] with a Lewis acid [3.4] 
lithium iodide for example [0.9] ring open the expoxide [0.2] and [0.2] we will 
[0.6] somehow magically [0.7] 
presumably from solvent [0.3] pick up a proton [0.4] and [0.2] we will l-, [0.
4] get once again [1.0] a [2.0] cation [1.3] the same cation [1.0] once again a 
Lewis acid and a [1.2] alcohol halide [3.4] the [0.3] the silver m-, mops up 
the chloride silver c-, silver chloride being insoluble [0.3] disappears from 
[1.9] the [0.4] the phase th-, from th-, from from availability as it were as a 
precipitate [0.4] and [0.2] we get this cation [1.9] here [0.2] proteination [1.
0] gives us the most stable [0.2] driven by m-, Markovnikov's rules [0.4] gives 
us the most stable cation [3.4] right [1.0] none of those cations exist very 
long er [0.2] er [0.3] they're all similiar cations [0.6] but [0.2] they don't 
exist very long because a group's going to migrate [0.2] one of these groups is 
going to migrate [1.1] depending on the migratory aptitude [1.1] and [2.0] 
we're going to get [0.2] a cation there [1.8] on this carbon [0.2] which is 
adjacent to the lone pair on the oxygen [0.2] which then [0.2] delocalizes 
pumps electrons into the system [0.2] and gives us a relatively stable cation 
[1.6] okay is that [0.4] does that make sense [0.3] is everyone happy with that 
[1.4] fine [0.5] so these are all [0.4] variations on a theme semi-pinacol type 
rearrangements [0.4] and [3.7] i have got [0.2] a few more examples here [3.8] 
and we we we we have to [0.3] sort of rush through them i'm afraid [0.2] once 
again this should be [0.4] i'll just check [0.6] yes it's in your handout [1.7] 
so [0.8] i-, probably i-, [0.2] more likely to be correct [0.5] if you [0.2] 
just leave it [0.4] with-, without copying it down [0.4] once again [0.2] these 
these are all [0.4] semi-pinacol rearrangements [0.3] nitrous acid [2.0] 
diazonium cation [1.7] once it falls off [0.2] and we then get [0.2] this group 
[0.4] migrating round [0.2] note [0.2] it's the trans [1.8] antiperiplanar 
arrangement that allows migration [4.4] because [0.3] yo-, [0.2] th-, [0.7] 
stress the antiperiplanar because of course [0.5] these are [2.4] actually in a 
trans arrangement aren't they [0.7] but they're not [0.2] in a suitable 
arrangement for migration [1.8] so it's got to be [0.2] this group here [0.9] 
and that group there [0.2] which are [2.6] going to be [0.2] are going to be 
the relevant er s-, have the relevant stereochemistry [0.5] and [1.2] of course 
we then [0.4] get [0.3] loss of a proton from the rearranged cation to give us 
a ketone [2.3] 
so we've made converted a [2.1] six member ring to a five member ring [4.3] 
here [1.1] we get two [0.8] different stereochemistry [2.0] in this case we've 
got [0.2] s-, the O-H and the N-H-two-cis [2.3] and [1.1] now [0.3] we have the 
possibility [0.3] of [0.3] two [1.0] conformations [0.4] mediating the [0.3] 
the process [0.4] here [0.7] we can have [0.2] this one formations of a cation 
[0.3] migrating group trans to the leaving group [0.3] note [0.2] the [0.2] the 
the f-, the fact is and i [1.1] must admit [0.2] t-, [0.3] confess to being 
slightly surprised or even baffled by this [0.4] that [0.2] that the [0.7] the 
azo group falls off and it appears this group does migrate selectively [0.2] 
even though [0.2] we don't get any of this neighbouring group participation [0.
2] and [0.2] and compare the aliphatic example [0.3] based on er [0.3] 
neopentyl cation that i gave you last week [1.2] where [0.2] where one got 
really a quite a mixture of products so [0.2] so even though [0.2] this is 
going to fall off very very quickly [0.2] you'd still get this this trans group 
migrating [2.7] and we get [0.2] the same [0.2] similar product to [0.3] 
previously the same product [0.2] but [0.2] we've got this other 
conformational arrangement available here [1.6] and [0.2] in this case [0.9] we 
now get [1.5] migration and [0.5] it's easier for the [0.2] hydride [0.2] to 
migrate [0.5] because it's trans [0.4] to [0.2] the leaving group [1.1] and so 
that's what happens and now we get a six member ring [1.7] there [0.7] of 
course [0.2] if we get ring-flipping [0.2] then we still are left with [0.3] 
the [2.1] the ring [0.2] methylenes [0.2] being trans to the leaving group [0.
2] so [0.3] ring-flipping doesn't really matter there [4.3] right [0.2] now [0.
2] i have [0.9] a huge range of other examples [3.2] so right [2.5] ring 
expansions it's a good way [0.2] to make to get ring expansions or contractions 
to give us er [0.4] er [0.5] by using rearranged [0.3] materials [0.4] here [0.
8] we start with cyclo- [0.3] hexanone [4.0] we then [0.5] react it with [0.4] 
diazome-, with sorry with nitro-, nitromethane [2.1] in base [1.3] nitromethane 
of course [0.3] is [0.5] er is somewhat acidic [0.2] so in base we form this [6.
2] highly delocalized anion [4.3] have to be very careful with diazomethane in 
base and don't let it dry out [0.3] of course [0.8] because [0.6] one 
interesting when i for my sins used to do [0.7] E-S-R spectroscopy [0.3] i er 
[0.4] we used to 
use [0.9] nitromethane as a s-, as a spin trap [0.2] and if you shake the flask 
containing the nitromethane in the base [0.4] you see a huge amount of radicals 
being produced in your E-S-R spectrometer [0.5] from goodness knows what source 
[0.3] but to me [0.2] the production of radicals spontaneous-, er [0.5] 
spontaneous-, [0.7] spontaneously [0.2] indicates [0.2] something alarming 
could be happening [0.3] and certainly is it says on the bottle [0.3] that [0.
2] it is quite explosive that [1.5] but [0.5] that is a good er er a good 
nucleophile and it will react [0.2] with [0.7] cyclohexanone there to give us 
[0.8] that alcohol [0.2] which then [0.5] we reduce [3.9] er [1.1] i really 
don't have to remind you the difficulties of making amines [0.4] aliphatic 
amines you can't do it simply by [0.4] er [0.9] just er just whacking in 
ammonia and and doing a nucleophilic substitution [0.4] type reaction [0.3] 
because there's [0.2] you get all these [0.4] er quarternarized ammonium [0.2] 
ions and that sort of thing [0.3] so [0.2] you [0.2] this is a good way to do 
to [0.2] to get an amine there [0.3] we then [0.8] we have that [0.3] we then 
reduce it [1.9] it would seem hydrogenation is the method of 
choice here [0.3] and [0.3] then [0.2] we treat [0.2] with [0.4] nitrous acid 
[7.5] to give us [29.0] the n-, the the [0.9] nit-, [0.2] the N-two falls off 
[0.2] the cation the er the [0.9] methylene group from the ring migrates and 
gives us the [0.3] the ring-expanded product [0.4] so we've got a seven member 
ring [2.1] now alternatively [10.6] we can use [0.3] diazomethane right [0.9] 
now [10.6] we can [1.9] get [0.5] a migration [0.2] but in actual fact we get 
two migrations happening [0.3] we get one path [0.3] gives us [25.4] gives us 
cycloheptanone [1.0] the other path [0.6] is [17.7] gives us that [3.0] that [0.
3] epoxide ring [0.4] in a [0.2] spirocyclic system again [11.9] of course [0.
3] you can then treat that [0.5] with lithium iodide [1.5] as we mentioned 
earlier [0.3] and [0.2] produce [0.3] the [0.9] cyclohexanone [29.1] 
i guess the trick is somewhere in the [0.2] the more basic conditions you use 
[0.3] in the [0.5] er [0.2] diazomethane synthesis [8.5] it seems to fall apart 
into [0.4] sort of more [0.2] more readily i guess would be [0.3] would be the 
answer there's more [0.7] i-, [0.6] it's n-, there's not so much thermodynamic 
control of the product [2.5] but [0.8] the important point is [0.3] that the 
root [0.2] at which you do this [0.3] does [0.2] affect what products you get 
[2.3] even though nominally you're getting the same intermediate there [0.6] 
but of course the intermediates are being formed [0.4] in a different way in 
one [0.2] you f-, you generate the N-two-plus [0.2] in highly acidic media [0.
3] in the other [0.2] i [1.6] it is it it is actually according to [0.3] to my 
[0.3] notes done in in acid but i guess it's not as [0.4] quite as acidic as as 
previously [12.5] another example [36.3] right do you get that occurring [1.6] 
no [1.9] what you get is [2.7] that [1.5] exclusively [1.2] gives us that 
exclusively [9.0] right [2.7] i [0.2] think we should leave the semi-pinacol 
rearrangement there [3.4] and move on [0.3] rapidly [0.5] to [2.2] the [1.1] 
Beckmann rearrangement and rel-, [0.2] related analogues [24.7] right [0.6] i 
hope you're all happy with that [0.2] idea of the semi-pinacol rearrangement [0.
3] we've seen [0.3] the pinacol rearrangement [0.4] guided [0.3] governed by 
the formation of this [0.3] er [0.3] highly stable cation adjacent to the 
oxygen [0.3] we've seen that we can modify that [0.3] using these semi-pinacol 
[0.8] type system [0.2] where [1.2] the classic the best example is where we 
have an amine [0.3] on the the adjacent group carbon rather than [0.3] er an O-
H [0.2] and then we get rid of that by diazotization [0.7] and you can see [0.
3] how [0.2] one can use that [0.2] particularly to form [0.2] rings that 
wouldn't [0.7] that are larger to form [0.2] ring-expanded systems [1.3] or [0.
9] ring-contracted systems [0.7] depending on the precise conditions you use [0.
5] but you can change [0.2] the ring size [1.9] it's actually very useful to be 
able to form a cyclo-, [0.2] er [1.0] heptanone [0.6] or a er seven member ring 
[0.3] it's a good it's a good skill to le-, to have in our armoury as [0.3] as 
synthetic 
chemists [0.8] okay so it's useful to be able to know [0.3] that these types of 
reactions lead us to seven member rings [0.8] albeit with some [0.2] 
complications [0.3] particularly with the [0.3] the diazomethane [0.8] the 
diazomethane is a [0.2] is a good is a really good reagent 'cause you can buy 
it from Aldrich [0.4] and so [0.2] that means that you don't have to go through 
several steps [0.3] and [0.2] it means that that that it much [0.2] quicker 
than [0.5] the ste-, the the the a-, the alternative methods i've shown you 
which [0.2] require you to synthesize [0.2] you know [0.3] where does that come 
from [1.1] well [0.5] goodness only knows [0.9] look at the look at the the m-, 
the the [0.7] two steps you have to get to even to get to the amine [0.3] in 
the [0.3] first synthesis [0.9] right [0.3] so [0.2] bit of a downer that you 
get a side product but you can convert the side product [1.8] synthetic utility 
[0.2] of [0.3] semi-pinacol rearrangements [0.3] and pinacol rearrangements [0.
6] it's [0.3] particularly [0.2] to my mind [0.2] where you want to form larger 
rings [0.9] okay [1.0] right so summarizi-, i've summarize that as i [0.4] 
always do after i've started the 
title of the next bit [2.1] the Beckmann rearrangement [1.6] like i say [0.2] i 
d-, [0.7] i don't like all these named reactions but [0.7] it is [0.5] helpful 
to have a title for a section [0.3] and [1.3] this is the rearrangement [11.1] 
now to my ignorant [0.4] poi-, er [0.2] point of view [0.5] the Beckmann 
rearrangement's the only [0.2] sort of [0.2] really big rac-, reaction of 
oximes [0.3] of course [0.4] in actual fact i will be [0.2] hauled over the 
coals if i said that in [0.2] the presence of so-, genuine synthetic chemists 
because they [0.3] have all sorts of [0.3] reactions and there's all sorts of 
chemistry of oximes that goes on [0.3] but this is [0.2] this is this is the 
biggie [0.3] er [6.3] perhaps i'm bias because this is the way that nylon is 
formed [0.4] for example [1.6] now [0.2] what is the Beckmann rearrangement i'm 
just reminding myself [0.5] ah yes [12.8] an oxime [1.4] there is an oxime [0.
2] now you can get an oxime [0.2] from [0.8] the reaction of a ketone [0.2] 
with [0.4] a [3.4] hydro-, with hydroxyl xylamine [1.6] ketone plus 
hydroxylamine [0.2] goes to [0.7] oxime [0.4] so we have [0.3] we would have 
our [11.2] er [11.2] 
normally we use hydroxylamine hydrochloride and buffer it with er [0.2] sodium 
acetate [0.8] just like your first year practical [0.5] you remember [0.7] the 
one that doesn't work [0.8] well [0.3] no [laughter] [0.9] but [0.3] well 
perhaps there are more of them that [0.4] don't work but the one where you make 
the semi-carbazone [0.5] and you were adding in buckets of sodium acetate and 
buckets of [0.4] er semi-carbazone hydrochloride it's s-, very similar [1.2] so 
you buffer it with sodium acetate [1.0] easy to produce oximes [3.0] now [0.9] 
if you've got an oxime with a specific stereochemistry [0.4] then [1.1] like 
that [0.3] then that's that's quite important [0.3] because [0.3] in fact the 
stereochemistry will [0.3] follow through in the process [1.0] what happens now 
we protonate we go to [8.9] to that [1.6] make that a good leaving group and 
that's going to fall off [3.6] and as it falls off [0.2] the group [0.3] trans 
to the leaving group migrates [34.9] so we're left with that horrible 
intermediate [0.2] which then picks up water [6.9] 
or i should say picks up hydroxide from water [7.6] to give us that [1.1] which 
then [0.2] tautomerizes [21.8] so the net result is [0.2] we've generated an 
amide [2.6] from [1.2] our [7.8] from from our oxime [20.1] 
right [0.3] now [0.3] pay attention [1.2] the group trans to the leaving group 
migrates [1.9] if you get some [0.2] of a mixture of material [0.2] which 
doesn't contain [0.4] just one group migrating [0.2] it means either you 
started off with something of mixed stereochemistry [0.7] or [0.3] the system 
[0.2] has [0.2] somehow [0.3] er [0.6] isomerized [0.2] in situ [2.3] now this 
one for example [0.9] let's show you what i mean [10.8] oh sorry what am i 
doing [0.8] C [0.6] [7.5] you get exclusively the phenyl group migrating [3.9] 
but [0.4] certainly [0.2] there are [0.6] there is some evidence to suggest [0.
4] that [40.5] you w-, [0.2] you might you get a trace of that [1.0] where both 
groups are aliphatic particularly according to [0.4] er March [1.4] March being 
a particularly useful [0.3] textbook for [0.3] sort 
of detailed synthetic information [1.0] so [0.8] there but what's happening 
there well it's not possible that that [0.6] that group can migrate it's not 
trans [0.3] what happens is [0.2] that you get [2.0] H-plus [0.2] and you can 
hydrolize the oxime [0.3] back to the ketone and the hydroxylamine [0.9] and 
then [0.2] you [0.6] reform it [27.3] you reform it as the other isomer [0.2] 
in actual fact you don't need to even go that far [2.2] you don't need to go 
that far as soon as you protonate it then you you you y-, y-, if you protonate 
across here [0.4] then you've got the option of the bond rotating [0.2] of 
course [0.2] but you're aware [0.2] because you did this practical in the first 
year [0.2] of the danger of adding H-plus [0.4] to [0.6] these sorts of 
derivati-, derivatives [0.7] because [0.2] they are it is a reversible reaction 
[0.7] and i guess [0.3] here [0.4] the [1.8] the exception to the rule [0.2] is 
only because [0.2] somehow you're getting some isomerization in the presence of 
the acid [3.8] but [0.4] on the whole [1.7] the trans migration is a [0.2] is a 
golden 
rule [0.9] so we can we can we can stick to that [0.4] now [11.4] you could do 
you could do other things [0.2] for example you can use [13.2] s-, sorry P-C-L-
five [2.8] you use P-C-L-five [0.2] in which case [0.2] you get [0.6] one of 
these inorganic [10.8] you get that which is a really [0.3] whizzo leaving 
group as it were [0.2] because of course it's going to form the phosphorous-
oxygen double bond [1.4] or you can [0.2] make [0.2] the tosylate [3.4] or you 
can use boron trifluoride [43.3] perit-, t-, er toluene sulf-, sulfinyl 
chloride [1.3] forms a tosylate which also is a good leaving group as you 
remember [0.4] the S-O-three-minus [0.2] because [0.2] para-toluenesulfonic 
acid [0.2] is extremely acidic [1.1] now the last point i wanted to [0.6] make 
on the er [8.3] sorry on the Beckmann rearrangement is [0.2] nylon [37.6] right 
[1.5] epsilon caprolactam [0.5] seven member ring [1.3] formed [0.2] from this 
oxime [0.2] the oxime is of course 
produced from [19.5] from that [0.8] then [0.3] we treat that with heat and er 
[0.5] it can be acidic or basic conditions [1.0] but largely heat [27.4] and 
that polymerizes [1.2] to form nylon-six [1.1] the six is [1.5] the number of 
carbons there in the monomer repeat unit [2.2] nylon-six-six is where you have 
two monomers and that's the one that you [0.5] may have seen the rope trick [0.
7] where you ra-, react adipoyl chloride [0.3] with [0.3] he-, hexane diamine 
[1.8] but [0.3] this is a commercial production of nylon [0.2] epsilon 
caprolactam is [0.2] a seven member ring [0.2] formed [0.3] from [0.3] 
cyclohexanone [0.4] and [0.3] in nineteen-seventy-five this was a compound that 
was in the news [1.0] when i was [0.2] relatively young [0.4] was most of you 
weren't even born i suspect [0.4] er [0.4] because it was the appr-, [0.4] 
epsilon caprolactam plant at Flixborough that blew up [0.4] creating [0.7] 
certain amount of local rearrangement as it were [1.6] [laughter] okay [0.2] 
well i think we better finish there thank you for your attention