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mick
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This is from personal experience.
In NMR experiments a D2O shake involves adding a drop of D2O to a solution of the compound which is usually dissolved in deuterated chloroform or
DMSO, shaking and re-recording the NMR. The proton signals due to alcohols, amines, amides, aldehydes and carboxylic acids will disappear due to
exchange and a signal due to HDO will appear.
You are right about the hydrogens in benzene not being ionised but I think the deuterium exchange is through an addition/elimination mechanism, it
occurs with hydrogen but that just gives non-distinguishable benzene ie no detectable reaction. The final products of sulphonation and nitration form
slower but are non-reversible and so are the ultimate products that are isolated and identified.
mick
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Marvin
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"You have quoted me incorrectly!"
No John, I didnt quote you at all.
"...This is UNLESS other reagents and conditions are present which will result in sulfonation"
"any such sulfonation would have to be fully reversible. (Reversibility looks unlikely, though, except under extreme conditions)"
Sulphonation is fully reversable. I suggest you read up on sulphonation of toluene, and of napthalene (compounds with more than one isomer), and the
effects of long versus short time periods and high versus low temperatures. These are effects that only have meaning for a reversable system.
Nitration is also reversable, but oxidation side reactions tend to eat away at yeilds.
Sulphonation does not have to be invoked as the primary cause, if you look at sulphonation or nitration which is commonly illustrated in degree
textbooks.
C6H6 + NO2+ => [C6H6NO2]+
It forms a meisenheimer complex, and this can either spit out H+ to form nitrobenzene, or NO2+ again to get back to where we started. The important
thing though is there is nothing special about NO2+. Its just the electrophile that results in production of nitrobenzene, its not the only one
though and to be fair its present in really tiny amounts. H+ is present in massive amounts so we'd expect the same thing to happen,
C6H6 + H+ => [C6H7]+ => C6H6 + H+
Thats the proton exchange mechanism I'd have my money on and judging by micks reponse I think he'd agree, but I dont see why the reversable
sulphonation of benzene would not provide a slower but also valid mechanism at higher temperatures.
Coming up with undergrad theoretical excuses for why something doesnt work after people have allready stated that it does - and then not bothering to
check in a book or online - is the action of an idiot.
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JohnWW
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Stop engaging in character assassination, Marvin! Just because someone says off-the-cuff that something works does not necessarily make it work. The
problem is that so many people who allege that some or another reaction works fail to fully specify the conditions of the reaction e.g.
temperature/pressure/acidity/solvent, omit to mention additional reagents which may be needed e.g. catalysts or acidifying agents, or mis-identify
reagents e.g. as H2SO4 instead of H2S2O7 which is standard for aromatic sulfonation. That is why what is stated to happen so often fails to agree with
theory, as in this sulfonation/nitration case. Please desist from penalizing me for these other peoples' failings.
Besides, aromatic sulfonation seems to be reversible only under conditions which are not the standard ones for sulfonation, particularly the presence
of water. As for aromatic nitration particularly of benzene, its mechanism is significantly different from sulfonation; and NOT ONE of several
reference books I have consulted, or a Google search, indicates that nitration may be reversible, to form the original reagents (particularly HNO3)
from the nitro-compounds and byproducts, under ordinary conditions in the same reaction mixture!
I observe that you did not further address the matter of the circumstances under which alcohols' deuteration can occur, which I also raised, in
your latest post. (Selective use of information, again.).
John W.
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Proteios
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chuckle.... im with marvin on this one... dont be so sensitive and show some humilty jonny!
and for those who might even consider the reaction....... so what if you get some sulfonation..... benzene is an absolute doddle to separate by
distillation
Oh yeah... and jonny.. when u be in a hole... stop diggin 
EDIT:
"Please desist from penalizing me for these other peoples' failings. ". 
... man thats a real nice attitude u got there jonny!
[Edited on 10-9-2004 by Proteios]
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JohnWW
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You added NOTHING new to the matters under consideration, Proteios. Keep out of polemics which do not concern you.
John W.
----------------------------------------------------
Please refrain from these kinds of comments. Everybody is free to post in this thread as long as he or she obeys the rules. Furthermore, enforcing the
rules is a matter of STAFF.
[Edited on 10-9-2004 by vulture]
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Proteios
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| Quote: | Originally posted by JohnWW
You added NOTHING new to the matters under consideration, Proteios. Keep out of polemics which do not concern you.
John W.
----------------------------------------------------
Please refrain from these kinds of comments. Everybody is free to post in this thread as long as he or she obeys the rules. Furthermore, enforcing the
rules is a matter of STAFF.
[Edited on 10-9-2004 by vulture] |
LMAO.... that brightened up anotherwise dull morning!..... barking orders about polemics indeed!... funny stuff!
However The Admin seem keen to desist this kinda behaviour.... so i guess im gonna have to leave my honour undefended this time.....but rest
assured I take such critisism very seriously.........
....chuckle....
[Edited on 10-9-2004 by Proteios]
----------------------------------------------
Same goes for you, if you have nothing to contribute to the thread, don't stir up shit.
[Edited on 11-9-2004 by vulture]
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BromicAcid
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Entery from the Chemical Abstracts, around 1955
If further questions result information from the actual article is linked below.
Also, additional information could be aquired by looking up the article on the origional preparation of C6D6 from benzene and D2SO4 at:
C.K. Ingold, C. G. Raisin, C. L. WIlson, C. R. Bailey and B. Topley, J. Chem. Soc., (1936); see also L. H. P. Weldon and C. L. Wilson. ibid., 235
(1946)
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JohnWW
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Because that is a Journal report of one researcher's apparent finding in 1954 or 1955, it is not necessarily authoritative. The test would be if
other researchers, on reading the report, found they could essentially duplicate it, and add other and more precise details as to the reagents used,
their purity, the purity of the alleged product, and the reaction conditions, and indicate or suggest improvements to the method. Only then would it
appear in textbooks or manuals.
Even if that equilibration reaction worked as stated, an enormous excess of deuterated reagent would have to have been used to obtain such pure C6D6
from C6H6 - possibly such that the synthetic method I described previously, involving reacting CaC2 with D20 and polymerizing the C2D2 produced to
C6D6 under heat and pressure, may be more economic. The author does NOT say how much D2SO4 he used per unit of C6H6 - a glaring omission!!.
That 1955 researcher does not specify relatively how much SO3 he "distilled" into his D2O, including also the density of the reagent he
used, although he says later he used "51-2% D2SO4" without saying how he measured this concentration. Bearing in mind that it is an
heterogenous reaction between two immiscible phases, sulfonation, although reversible under certain conditions requiring water/heavy water to be
present, proceeds unacceptably slowly with H2SO4, and would be even slower with D2SO4 because of the greater mass of D; and MUCH slower again with
diluted 51% D2SO4. He, in fact, says he had to shake the mixture (consisting of two phases, the C6H6 and the aqueous diluted D2SO4) vigorously for 10
days under dry N2!! For a large-scale production process, that would probably be regarded as an unacceptable holdup time for a single reaction step,
in my opinion as a chemical engineer. Moreover, he does NOT state the % yield of equilibration reaction, which would be reduced from 100% if the
reaction was not fully reversible - another absolutely glaring omission!
Either that, or it was not D2SO4 he used, but instead D2S2O7, deuterated "fuming" sulfuric acid (and the reaction was then reversed or
partly reversed by adding D2O), which reagent, I repeat, is standard for sulfonation in chemical industry.
John W.
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mick
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If you ran it as a continuous process industrially a residence time of 10 days should not be a problem
mick
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Proteios
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There is nothing wrong with this experimental (if you read the whole thing.. there is enough info to reproduce the experiment). Clutching at straws
like.....not everything in the literature is correct, or ....but some other side reactions are theoretically possible, is the last refuge of a
academic scoundrel.
I could reproduce this work fine.
1) Distill your SO3 into into an ampoule with a teflon ring style seal. Distil some of this into your D2O.... probably a real fiddly reaction.... but
straightforward. Mass balance gives you your %. Normally you wouldnt bother saying things like this in an experimental....its too trivial.
2) Its stated the reaction is an equilibirum. At the beginning all the H is on the benzene.... all the H/D is equally in all positions. If it were
me.....I would just use a ratio of 1000D:1H for a single pot synthesis. That should give you 99.9% D benzene.
If you were an isotope lab you would probably do this in 2-3 steps with 2-3 different H/D water.... all of which are easily recylable.
As for the sulfonation.... give it up! As i said earlier.... benzene is v. easy to separate by distilation anyway and sulphonation usually requires
much more extreme circumstances.
If you check the jpg you will find that this technique is 'similar'.... to that used by...... i.e. it has already been reproduced: this is a
GOOD AND STANDARD LITERATURE SYNTHESIS ...... ACCEPT IT!
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mick
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I have tried to do a citation index search for the ref above to see how many people have mentioned it, but I cannot get through from home, I will
check it out at work.
I think the people who did this stuff in 1954 did a good job with the stuff they had. I class myself as an organic chemist now, but I do not think I
would have any problem following what they said and expect 90%+ yield on the first run. I could even check it out on the old NMR (the one where I work
is obselete but it still works) and tell you if the if the second deuterium goes para to the first. I could even do a rate of exchange graph. The
only problem I have found with old information is the analysis is not as good as today. The practical stuff is better than today. Sintered glass
filters are good for increasing your yield on a small scale, glass does not show up on most analytical techniques but when it implodes under vacuum
where has all the glass gone, I think it increases yields on a research papers.
Sorry about this but you should not critisise the work of a good chemist just because he did it in 1954.
Peer review is good and I am sure the people who published the paper in the 50's were checked out.
Unpeer review does not sound quite right to me.
mick
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JohnWW
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| Quote: | (cut) I would just use a ratio of 1000D:1H for a single pot synthesis. That should give you 99.9% D benzene.
(cut) |
1,000 Ds to replace 1 H on benzene? An UNACCEPTABLE waste, having regard to the cost of D2O used to make the D2SO4, as well as the 10 days holdup
required!! Together, these two factors would require enormous reaction vessels to be used, for very small amounts of C6D6 produced. The alternative I
suggested, via CaC2 and C2D2 and polymerization, is certainly more economic than that.
Having run out of better ideas, you now stoop to calling me an "academic scoundrel"! Who is REALLY the "academic scoundrel"?
Certainly, anyone who is so wasteful with expensive reagents like D2O just has to be the real "academic scoundrel".
It looks like just "sour grapes" on your part.
John W.
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mick
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But? if you ran it as a continuous process with the right pumping speeds and the right take off rate, you should be able to re-circulate most of the
stuff
mick
typo
typo 2
Typo 3
[Edited on 11-9-2004 by mick]
[Edited on 11-9-2004 by mick]
[Edited on 11-9-2004 by mick]
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mick
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It is a bit like fractional distillation.
mick
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Proteios
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man... for a guy who claims to be a chemical engineer.... you certainly do make some dumbass statements.... I take it you now accept the reaction is
1) CORRECT... and youve given up that.... 'but i can think of a possible side reaction... therefore.... nomatter what teh literature says... it
cant work'
2) IT IS SIMPLE... doesnt require handling gases... high temperature... with all the cracking problem that will ensue
Seeing as you clearly arnt able enough to figure it out for youself....... The 1000 fold excess of D2O will be 99.9 % pure by the time you
finish...... well you could either use it again..... sell it on.... or send it back to the D2O plant for repurification. The idea that you would
throw it aways is so stupid Im shocked that anyone would be so limited to suggest it.
I deal with lots of isotope synthesis..... Yield isnt really something that bothers me. The factors considered in a synthesis are
1) SIMPLICITY.... a point on which the one pot aqueous synthesis wins hands down on.
2) Ease of purification..... in this case V. Simple
3) recovery of isotope..... again.... in this case, V. simple
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JohnWW
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Just very slow, using or least requiring the purchase and acccommodation of a grossly excessive amount of an expensive reagent (D2O) even if it may be
possible to reuse some of it, requiring an ENORMOUS reaction vessel for the amount of desired product produced (because of the enormous excess of D2O
needed and the 10-day holdup), and hence inefficient and excessively costly, that's all. Even if the reaction works, these factors would
certainly call it into question as to its commercial practicality, and must make it uncompetitive with alternative methods involving direct use of
D2O, e.g. via carbide, on a large industrial scale.
Unless, of course, suppliers, or a monopoly supplier like Sigma-Aldrich, of deuterated chemicals simply do not care how much they cost to produce even
if there are cheaper methods, and can rip consumers off as the result because of inadequate competition - at least until patents for the cheaper
methods which they are "sitting on" expire. You say, "I deal with lots of isotope synthesis" - perhaps you work for such a company
which is deliberately suppressing cheaper process methods in this way?
By your own admission, "Yield isn't really something that bothers me" means that you have NO concept or appreciation of process
economics, Proteios, as well as no regard for the efficiency of reactions involving expensive reagents. Go back and do a course in it, at your local
chemical engineering department (where do you live?), and then come back here. Ordinary (non-monopoly) chemical manufacturers would go broke if their
staff had your sort of attitude.
John W.
[Edited on 12-9-2004 by JohnWW]
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Proteios
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Yeah... thats right... yield doesnt bother me..... Im interested in gettin the right isotope in the right form.
Again, the important factors are:
SIMPLICITY
RECOVERY OF ISOTOPE
D2O is cheap.... as i have said previously if you were doing batch runs you would do the reaction 3 times..... each with a H/D ratio of 10:1.
Take about a month.....and yeah... i know what your gonna say... thats commecially unacceptable.... but thats just wrong....the labor involved, which
will be the largest cost in all of this, is nominal.... it only takes a few hours at most....
The alternative requires
1) Custom made kit
2) Lots of labor
3) Difficult conditions. Its funny that you were prepared to rubbish the literture synthesis upon little other than prejudice... and now you say that
another reaction... for which you have no conditions, or procedure will be superior. However the reaction involves temperatures capable of breaking
bonds.... this is gonna be a messy reaction. The conditions are gonna be awkward.... high temperture gases, and probably high pressure too. The
separation of products may also not be trivial.
By comparison the LITERATURE single pot synthesis is better. You also sound like unless a synthesis is possible on a kilotonnes scale... its not
worth doing. Isotope synthesis does not work like this.
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Marvin
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"Stop engaging in character assassination, Marvin! "
You post opinions in areas you clearly have weak understanding, you argue that you are right providing no new information and you fail to check
anything in books or on the internet. If you consider these part of your character then yes, I am engaged in character assination and will do so as
long as you give me cause to.
"The problem is that so many people who allege that some or another reaction works fail to fully specify the conditions of the reaction "
I'm sorry you think the brand of labcoat, the god you have to prey to beforehand and the exact size and shape of the ceiling tiles were not
mentioned. We'll try harder. The reaction itself was described correctly, so the excuse that you disagreed because other people make mistakes
doesnt hold water, deuterated or otherwise.
"That is why what is stated to happen so often fails to agree with theory."
No, you were spouting theory based on an assumed mechanism, they were describing what actually happens by experiment. The fact that your grasp of
theory is insufficiant to describe the real world is something we all have to deal with, if it were possible to predict everything perfectly we
wouldnt need the lit. However when presented with working and reliable information that disagrees with your understanding you automatically assume
they must be wrong, and you post a rapid reply based on your own gut reaction that you then defend regardless of how much evidence mounts against it.
This goes among a vast number of other rapid thoughtless posts you shotgun over the whole forum without aparently bothing to check ANYTHING. I cant
remeber you posting one useful reference, one quote from a book, one relavent URL to back up your arguments.
"Please desist from penalizing me for these other peoples' failings"
Perhaps a summery of the d6 posts will bring this issue into focus.
BromicAcid claims sulphuric acid and benzene can be used to make d6 benzene.
You assume a mechanism, and disagree based on it.
BromicAcid posts a mechanism and explains it and Proteios agrees.
You object with a reason and ask for a reference.
mick points out an example of why your objection isnt valid.
BromicAcid gives a reference and a quote that supports the mechanism and the practical observation and asks why you think your objection is still
valid.
You answer with an incorrect assumption about nitration, and electrphilic substitution generally.
I mention nitration and sulphonation standard mechanisms support the mechanism and that these are in any standard degree textbook, trying to indicate
gently you should look them up.
You restate your case exactly as before aparently without checking or adding anything new.
mick posts in support of the exchange mechanism,
I post an explanation of BromicAcids mechanism in the context of nitration.
You blame inaccurate or incorrect descriptions by other people for the reaction failing to agree with 'theory'.
BromicAcid posts an entry from chemical abstracts, and a scan of a reference with enough information to actually do the experiment and predict the
success of the result beforehand.
You argue that a single reference isnt conclusive and that other researchers would have to have succeded for it to be valid. Dispite this reference
being in support of 2 other previos reports having claimed the same thing. You also argue that the conditions are not accuratly enough described
(They are if you want to replicate it) and that amounts of reagents used were not mentioned (Irrelavent because this is an isotopic exchange and they
give a value for success based on ratio of reactants so you can predict this).
Now. How is it other peoples failings that are the cause exactly?
"Besides, aromatic sulfonation seems to be reversible only under conditions which are not the standard ones for sulfonation, particularly the
presence of water. "
Hmm, presence of water, other than its formation from the reaction going forward for example? Its not the case with Oleum, but this is not common in
labs, most compounds will go with sulphuric acid alone including benzene if heated. You are letting what goes on industrially cloud the actual
chemistry. Indistrial conditions are one specific case of how a reaction can be done, not the be and end all of the reaction.
"I observe that you did not further address the matter of the circumstances under which alcohols' deuteration can occur, which I also
raised, in your latest post"
At the time you wrote this, and for several hours before your post, my post in the other thread relavent to alcohol exchange covered this, but since
you require some extra information....
The reaction occurs rapidly monday to saturday in any month with an 'r' in it. For protons the reaction fails 18 additional days in the
year sheduled in advance during the remaning months. Deuterium being a minority isotope only gets 2 weeks off a year due to its smaller union. The
unions dont merge because protons object to deuterons eating all the free food during meetings and singing 'we ate all the pies' as a
misdirected backlash at mass predudice. Chemists are advised to take their holiday during this time and to sign up for a newsletter indicating when
either union plans to go on strike.
"Selective use of information, again"
As opposed to discussing things in the complete exclusion of information, I assume.
"possibly such that the synthetic method I described previously, involving reacting CaC2 with D20 and polymerizing the C2D2 produced to C6D6
under heat and pressure"
Hmm, you mean the method Organikum posted a scan of a detailed refernce for over a year ago that gives specific conditions and uses lithium carbide to
avoid contamination with residual Ca(OH)2?
For conditions to make d6 benzene from D2O the acetylene way check out Organikums 30-3-2003 post in the first page of the benzene thread.
"For a large-scale production process, that would probably be regarded as an unacceptable holdup time for a single reaction step, in my opinion
as a chemical engineer. "
Oddly enough my textbooks fail to mention d6 benzene as a high tonnage chemical, I'll just scrawl it in above sulphuric acid and leave the amount
per year blank.
mick, thats a good point, if it were to be done industrially you wouldnt use a batch process, youd use a counter current continous process and get
99%+ d6 bezene out one end and probably <5% D2SO4 out the other. Another possability is that someone would work out conditions for making a stable
emulsion and that would really decrease the time needed.
Proteios, I agree, 1000:1 would impact on the deuterium content of the D2O only very slightly, but getting th D2O back would be problematic. Cost is
usually not much of an issue as only tiny amounts are usually needed (eg tracer studies) and ease of production and speed are important. Side
reactions might cause some loss, sulphonations etc with such a large excess of D2SO4, might make seperation difficult afterwards.
Again, its thinking about a problem with different objectives than usual. Lab chemists need to be flexible, its good to have this kind of input.
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mick
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The paper BromicAcid found has been cited at least 48 times and many of these are from pre-net days, when you had to spend time and money to get a
reference, if it was a waste of space I do not think anyone would have bothered. I read in another thread about scams. The current one seems to to
publish a crap paper in a crap journal and you and your friends publish as many papers as possible all citing the same paper and when you apply for a
research grant you get priority because you have been cited.
I was luck, I got my name in print in 1992 so people refer to the stuff because it is on the net (22 hits so far, nice to know that some one has read
your work and thought it was worth mentioning). If it had been a few years earlier, no abstract or full text on the net I am sure no one would have
bothered. Any way back to subject, for most applications 99%+ isotopic concentration would be OK, it is only when you are talking 99.9%+ etc you end
up a different situation. Then as few hydrogens get near to your process as possible, and cost would not be a consideration.
mick
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JohnWW
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That is why a lot of incorrect, or grossly inefficient, chemistry gets into print - because being cited, i.e. getting one's name in print, gets
you research grants, scholarships, or jobs. I wonder how much of the reported uncorroborated results were simply "cooked".
That was probably why, back in 1954 or 1955, a highly inefficient method of producing hexadeuterobenzene, was submitted to the J.A.C.S.. I simply
cannot believe that a much more efficient, and certainly more rapid, method of producing it has not been discovered and developed for large-scale
production in the 40 years since then. If it is still used for the purpose, the commercial producers must be simply "sitting on" the patents
for the better methods - and are certainly not letting out any trade secrets.
John W.
[Edited on 12-9-2004 by JohnWW]
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JohnWW
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Marvin: Is regurgitating what has already gone all you can do, along with name-calling? Are you that lacking in originality and credible
scientifically-based responses? People, especially on this forum, are not fooled by such sheer quantity of repeated verbiage, especially as it has
been selectively picked and "slanted".
I stand by what I have written, and would only alter it to consolidate it. You do not seem to know the difference between merely doing chemistry, and
doing good chemistry and especially efficient and economically viable chemistry (with regard also to my previous post on this thread), unless it is
just a case of "sour grapes" for not previously appreciating this.
John W.
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mick
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Pass
mick
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Proteios
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this is starting to look very undignified jonny......
Having been shown to be catagorically wrong on the point:
QUOTE JONNY
"That sounds MOST unlikely, because the H atoms in unsubstituted benzene, for all practical purposes, do not ionize, i.e. are completely
non-labile."
"Because of the extra aromaticity stability associated with benzene, and its symmetry, such easy protonation by a simple non-oxidizing acid does
not sound likely. "
You now say... well its very inefficient..... a point which is again wrong in every important aspect, and that you BELIVE there is a better reaction
to produce tonnes of the stuff in a wink of an eye for the cost of an extra value meal..... but of course offer nothing to back this up. This
argument has the logical appeal of "Antractica doesnt exist because I have never seen it". The bottom line is Jonny that you were
ABSOLUTELY WRONG in you initial arguments that this synthesis was impossible. ACCEPT IT.
If I had to do and experiment with D6 benzene.... i would buy the stuff.....its cheap and easily available. If i had to make the stuff..... I would
use the above literature proc. Its SIMPLE, labour effiecient, and it works. The idea that I would waste months figuring out reaction
conditions/purification protocols and several tens of thousands of dollars building kit for some fiddly hot gas reaction somehow doesnt have the same
appeal.
AGAIN THIS IS LAB SCALE WORK.... NOT HEAVY INDUSTRY!
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Proteios
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| Quote: | Originally posted by JohnWW
Marvin: Is regurgitating what has already gone all you can do, along with name-calling? Are you that lacking in originality and credible
scientifically-based responses? People, especially on this forum, are not fooled by such sheer quantity of repeated verbiage, especially as it has
been selectively picked and "slanted".
I stand by what I have written, and would only alter it to consolidate it. You do not seem to know the difference between merely doing chemistry, and
doing good chemistry and especially efficient and economically viable chemistry (with regard also to my previous post on this thread), unless it is
just a case of "sour grapes" for not previously appreciating this.
John W. |
always banging the chemical engineer drum about sulfonations..... and always complaining about character assassinations:
"Stop engaging in character assassination, Marvin!"
posted on 9-9-2004 at 07:49 PM
"There is nothing more for me to say on this matter; I know what the facts are. Please stop engaging in hubris and character assassination, and
selective use of information, Chemoleo, for having been beaten to the point. Are you jealous? "
posted on 8-9-2004 at 02:41 AM
Im sure ive said this before: but for someone who gets things wrong as frequently as you jonny, youve got a real nice attitude.
Heres a line for the narrow minded.....You dont seem to understand the difference between Heavy industry, excomony driven chemistry, and isotope
synthesis.
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JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
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Are you not aware, then, that Sigma-Aldrich (in particular) make and sell commercially isotope-substituted chemicals, especially deuterated chemicals?
Production of deuterated and other isotope-substituted compounds thus has EVERYTHING to do with process efficiency and economics.
Even for small laboratory-scale preparations of deuterated compounds in university laboratories, especially if a constant supply of them is needed and
the desired ones are not commercially available, I am very sure that the university's Regents would want the maximum economies in the use of
expensive reagents. No university has unlimited funding, in this day and age - even if things were different in the mid-1950s.
John W.
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