Sauron - 25-1-2007 at 02:44
While looking into TCCA's selectivity (it catalytically oxidizes secondary alcohols while leaving primary alcohols alone) it occured to me that, used
in conjunction with its close relative CC (TCT) this could be an interesting alternative to the rather tedious classical stepwise chlorination of
glycerine and the brute force oxidation of the 2-OH.
Thus, TCCA/KBr in DCM over wet sand would transform glycerine to sym-dihydroxyacetone.
Or TCCA in acetone with a tertiary base as H-scavenger. Same product.
This product would then be reacted with CC in usual manner (CC/DMF complex) to give either the mono chloroacetone, or the 1,3-dichloroacetone, both of
which are useful, if rather unpleasant compounds depending on molar ratio of CC.
The classical chlorination of glycerine with anhydrous HCl is a mass with complex azeotropes and messy distillations. (See the Org.Syn. 2, 22, p.22
and 29.)
Anyone have any thoughts on this?
[Edited on 25-1-2007 by Sauron]
[Edited on 26-1-2007 by Sauron]
Ozone - 25-1-2007 at 17:19
Almost everything with glycerol (of DHA) turns into brown/black crap with a multitude of products. The standard HCl Sn1 route should focus on the 2°C
OH to yield 2-chloro-1,3-dihydroxy propane (the temperature must be carefully controlled and stoicheometry carefully obeyed). Still, you should
get...loads of other crap.
I have started a thread on valorizing glycerol here:
http://www.sciencemadness.org/talk/viewthread.php?tid=7036&a...
I thought it might be of interest to you.
Cheers,
O3
Thanks for the books! I wish I had *more time* to check them out
.
Sauron - 25-1-2007 at 17:55
One might expect HCl to attack the secondary hydroxyl first but that jut is not what happens with dry HCl gas.
Org.Syn. 2, p.33 (1922)
59-63% yield of the monochlorinated product, in terminal position.
And chlorination with dry HCl in presence of AcOH gives 1,3 dichlorohydrin. 55-57% purified yield (after two distillations.
ibid, p.29
And this oxidizes to sym dichloroacetone (ibid., p.211)
The 1,2 dichlorohydrin does not form, or forms in traces only.
I am suggesting that TCCA will form the 1,3-hydroxyacetone selectively.
No chlorination will take place in the short time period it takes for the oxidation.
Anyway I am going to try it as soon as I can get some TCCA, I have plenty CC on hand. I'll report what happens.
Ozone - 25-1-2007 at 18:13
Ah! I did not catch the HCl(g) part. Thanks for the reference (orgsyn.org gave no hits on glycerol, trichlorocyanuric acid or TCCA)! I have the
collective volumes 1-5 on the shelf here, so I'll check it out. BTW, do you know where I can get vols. 6-9? I have found 1-5 three times
(I donated one set to my work library, gave one set to my friend, and kept one).
The beast is the 45-43% of unreacted crap and side products. I will have to try this, but I worry about *mostly* 1) condensation of DHA to dimer (and
tar) and 2) unwitting formation of vessicant/lachrymatory products. Perhaps we can compare notes on this one (I have TCCA tabs, the big ones).
Methinks temperature and pH control a "biggee" here.
Cheers,
O3
guy - 25-1-2007 at 18:23
Why is it only selective to secondary alcohols?
Sauron - 25-1-2007 at 18:49
Please read the references. They contain a proposed mechanism.
Synth.Comm 22(11), 1589 (1992)
Synthesis 2006, 12 p.2043
particularly Schehe 4 in second ref.
However as reference 1 demonstrates KBr is not required nor is wet SiO2.
I suspect that the high dilution employed in th Iranian procedure is merely a nuisance since the Synth.Comm procedure omits this, the wet sand, and
the "catalytic" KBr in favor of stoichiometric amounts of TCCA and use of a H-scavenger,
The selectivity appears to be kinetic. Oxidation of secondary or benzylic hydroxyls is so much faster than primary hydroxyls so as to allow control.
The same is true of side reaction chlorination. In one instance we see tertiary amine being used to scavenge HCl and in the other, high dilution
accomplishes same goal. In the latter case the use of KBr along with the TCCA in wet media allows TCA to liberate HCl, proceeding to Cl2, HOCl,
interacting with KBr to form hypobromite and the proposed active oxidizing specie Br+.
In both cases the rate for secondary (and benzylic) alcohols is much faster than for primary alcohols. Both references amply demonstrate such
selectivity. Mixtures of primary and secondary alcohols give quantitative conversions of the latter and zero conversions of the former. Molecules
containing both primary and secondary hydroxyls are oxidized only at the secondary site.
Selective for secondary and benzylic hydroxyls.
Makes you wonder about allylic ones.
[Edited on 26-1-2007 by Sauron]
chemrox - 10-2-2007 at 15:06
conversion of glycerols is a very important subject for my fuel projects. I'm going to check Mood's thread next. The usual and assumed method in
biofuels is to esterify with MeOH or EtOH. It's a problem. The resulting esters have no particular use as they are and are there because they drop
out of the fuel. A facile method for making them into chloroacetone in oil solution would be most welcome except separating them might be a problem.
I suppose the oil would be heated and the products collected and condensed from vapors (nasty). This is all acedemic because Saurons method wouldn't
work in situ (waste vegetable oils or corn oil)... but a process that would convert glycerols in situ into useful reagents would be most exciting.
Sauron - 10-2-2007 at 16:13
@O3, did you ever get round to trying TCCA (trichloroisocyanuric acid) on glycerol?
chemrox - 10-2-2007 at 18:39
I can't believe I wrote that; "Mood's thread.." I meant Ozone's thread. Sorry guy...
Ozone - 10-2-2007 at 21:50
I suppose it's a good thing that my mood is good
.
Anyway, @Sauron:
I'm feeling guilty about it, but I have not yet had the chance to try it! I 've got the chemicals/equipment, but not the time. Working full time with
a PhD on top (nevermind my *very* tolerant wife) has my schedule bursting at best. And I just found out I have to give a Dept. seminar Monday (my
advisor decided to leave (*really* bad timing), and this is to inform my new
one...).
I'm giving it my best to try it out the week after next (as I have a qual. next saturday). Shit^10.
I really think that this rxn will work, which is why this is bumming me out
.
I think that chloroacetone will suffer the same fate as my quantitative acrolein synthesis!
All my best,
O3
Sauron - 11-2-2007 at 00:23
Just bear in mind that chloroacetone is a really nasty lachrymator and early tear gas, and maybe worse, so take appropriate steps as you must have
with acrolein.
I would certainly be interested in hearing about your quant.prep. of acrolein, all I have are the Org.Syn. procedures.
As you probably know acrolein is probably best stored as an acetal. This is generally true for many aldehydes, more so for nasty ones.
Ozone - 11-2-2007 at 08:52
Thanks, I was alluding to that with my acrolein comment
. 1 drop of acrolein
outside of the hood (to eamine a water interface in a test tube) mafe my face feel like it was burning off. It is so lachrymatory that you don't
notice the smell...
Chloroacetone vile, but proof of concept and needs to be done.
Cheers,
Lee
Sauron - 11-2-2007 at 09:06
Ugh. I think acrolein is also on that short unsweet list somewhere between 10-20 in number of proven human carcinogens.
Something of course no one seemed to know when as a boy I dripped some glycerin on finely powedered KMnO4 in my lab in Dad's garage.
Oh well, It hasn't killed me...so far.
Ozone - 11-2-2007 at 09:23
Me neither,
But 'tis a good idea to keep it in the hood. I'm thinking about making some functional polymers with it. The way I see it, in this day (and under
these circumstances) any time you take something all natural and safe (note: natural does not immediately imply safe, as many seem to think) into a
hazardous industrial chemical, it's a win.
I want styrene from lignin, damnit.
The KMNO4/glycerine trick is a classic, I did it many times as well. Gone are
the days of "Chemistry for boys", cans of ether at the drugstore, and chemists that did anything but make goop as children.
Cheers,
O3
Sauron - 11-2-2007 at 09:58
Didn't the Gilbert Chemistry Set, as sold c.1960 in metal chest, w/many rectangular glass bottles, include an oz. or so of red P?
I recall there were two dark red pwders, one was logwood. I can't think of what else the other could have been but red phosphorus.
(Watch, the tweakers are all going to snap up all the collectible Gilbert sets on the market.)
Ozone - 11-2-2007 at 10:10
Ah yes *nostalgia* the hematoxylin dye; there was also eosin. I don't remember if there was red P, though (my Gilbert/Chemcraft set came in the late
'70's with much fanfair).
Ah, the good old days.
If we can selectively (stoicheometrically) add 1 Cl, I think that atrazine analogues might be feasible from CA.
All the good sets already seem to go to suspicious sounding buyers (usually with little or no history/feedback) on a certain popular auction site.
O3
Sauron - 11-2-2007 at 12:16
Maybe it wasn't red P after all. Cochineal? Damn, these memories are 45 y.o. I never had much use for the cochineal or the logwood. I don't remember
Eosin being in mine.
Ozone - 11-2-2007 at 12:36
I just ruined the carpet. I think I might have confused the Eosin with another
kit I has at the same time, Boreal or Carolina? It had some slides, methylene blue, Eosin and canada Balsam. I had a decent microscope dad gave me,
so I did not use the one that came with the kit.
Every kid needs a microscope. Especially the new, cheap ones that hook up USB
to your PC (hey, 200x for ~$50US--who's complaining about cheap optics); I am thinking of picking one of these up to play with.
Oh, yes, once we have made a ton of chloroacetone, what industrial uses do you propose for it (you must create the market with the product...).
Cheers,
O3
Sauron - 12-2-2007 at 07:02
I'd Google for that or hunt in Ulmann's or Kirk-Othmer. That's technology. I let the engineers do all the real damage.