Axt
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Chlorination of Aniline
I've tried two ways, one by bubbling Cl2 through a solution of aniline in DCM (dried with P2O5) though this only resulted in immediate masses of
resinous crap. This method was from journal literature (Am. Chem. J.) I lost the original article. Though I substituted chloroform with DCM, the
original text follows:
<i>"The trichloraniline used in this preparation was made by the excellent method of Victor Meyer and Sudborough' as follows : One hundred grams
of freshly distilled aniline were dissolved in one kilogram of chloroform, which had been washed to free it from alcohol, and thoroughly dried. The
vessel containing this solution was immersed in a bath of ice and water, and dry chlorine passed through the cold liquid, until it was saturated,
which occupied from twelve to fifteen hours. It is advisable to introduce the chlorine through a wide tube, as there is danger that a narrow one will
be stopped up by precipitated trichloraniline chloride. The precipitate formed by the action of the chlorine was freed from chloroform by means of a
filter-pump, dried and washed with water, which removed all the compounds of aniline except the trichloraniline. The yield was good, as 117 grams of
trichloraniline were obtained instead of 211 grams, that is 55.4 per cent, of the theoretical amount."</i>
I have no intention of trying that again, toxic rainbow coloured resinous crap is hard to clean. I never dried the red MERK aniline, and the Cl2
derived from TCCA/HCl was dried through a flask of CaCl2. I suspect a small amount of water present is the reason for the dramatic failure.
I'm aware of US2675409 which first converts the aniline to its hydrochloride via reaction with anhydrous HCl before the chlorination. Though again
stringent exclusion of water is a must.
For a second try I used H2O2/HCl/AcOH, this seemed to have promise though is a hot reaction and good cooling is needed. Into a well cooled solution of
5.5g aniline in 60ml AcOH and 100ml 32% HCl was added small portions of 50% H2O2. The solution turned yellow to green to blue, after taking it out of
the freezer on warming an exotherm resulted which precipitated an olive drab coloured substance. This is too simple for the product to be
trichloroaniline, but what is it likely to be? This green compound is also seen in the resinous crap from the previous reaction of aniline + Cl2.
So I ask if anyone has experience chlorinating aniline through convenient means? Also if anyone has information on physical properties onf
mono/di/trichloroaniline? especially colour. Also If anyone knows what the reaction of aniline with AcOH/NaOCl yields?
I hate aniline very much.
[Edited on 16-12-2007 by Axt]
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solo
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Reference Information
Chlorination of Benzidine and Other Aromatic Amines in Aqueous
Environments
R. L. Jenkins, J. E. Haskins, L. G. Carmona, and R. B. Baird
Archives of Environmental Contamination and Toxicology Volume 7, Number 1, pg. 301-315, 1978
Abstract.
The fate of aniline, N,N-dimethylaniline and benzidine in chlori-
nated waters was investigated. Conditions were controlled to approximate
the process chlorination of raw water supplies and wastewater secondary
effluents.
As the molar ratio, (C12)/(amine), was increased, amine depletions
increased and leveled off at about (C12)/(amine) = 1. Depletions in distilled
water with 'free' chlorine were somewhat higher than those in activated
sludge/secondary effluent with combined chlorine. For each amine the num-
ber and type of products appeared to be independent of the water matrix and
the ratio, (Cl2)/(amine).
For the monophenyl amines ring chlorination was a significant depletion
pathway. Extended chlorination of aniline yielded a precipitated product,
while the N-substituted amine, N,N-dimethylaniline did not yield a solid
product. In contrast to the monophenyl amines, when benzidine (p,p'-
diaminobiphenyl) was exposed to chlorinated waters, a solid product resulted
immediately. Infra-red analysis of this product indicated a polymeric struc-
ture with no ring chlorination. GLC analysis of the chlorination supernatant
showed no ring substituted isomers of benzidine.
[Edited on 15-12-2007 by solo]
Attachment: Chlorination of Benzidine and Other Aromatic Amines in Aqueous Environments .pdf (624kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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solo
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Reference Information
A Study on the Synthesis of 2,4,6-Trichloroaniline by Chlorination of Aniline
김철웅, 진항교 , 이수복 , 이정민
HWAHAK KONGHAK Vol.28, No.2, 230-236, 1990
Abstract
For the chlorination of aniline salt to synthesize 2,4,6-trichloroaniline in the solvent of chloroform, the reaction mechanism was suggested and the
reaction kinetics was examined. The reaction rate constants were esti-mated by using the experimental results obtained in the range of 10-40℃
and the equations of reaction rates, which were derived from the reaction mechanism. The results calculated by applying the reaction constants to the
theoretical equations of reaction rates were well agreed with experimental results. The reaction rate of formation of 2,4,6-trichloro-aniline from
aniline salt is 9 times greater than that of 2,6-dichloroaniline, and the activation energies of these two reactions are almost same. Thereforem the
increase of 2,4,6-trichloroaniline yield cannot be expected by controlling the reaction temperature, and the obtainable maximum yield of
2,4,6-trichloroaniline is about 90%.
Attachment: A study on the synthesis of 2,4,6-trichloroaniline by chlorination of aniline.pdf (342kB)
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It's better to die on your feet, than live on your knees....Emiliano Zapata.
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Axt
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Thankyou for those articles.
I just tried again, this time I wanted to see what would happen if I left the P2O5 as a slurry in the solution. Into a solution comprised of 5g
aniline in 100ml chlorobenzene was added a spoonfull of P2O5. This was swirled and let stand for 30 min. Chlorine was bubbled in and soon the solution
was thick with a mustard coloured precipitate. Its still going as I type.
I found the colour of trichloroaniline <a href="http://physchem.ox.ac.uk/MSDS/TR/2,4,6-trichloroaniline.html">here</a> as being purple
fibres! though <a href="http://www.chemyq.com/En/xz/xz1/3378borov.htm">here</a> as being light yellow needles. I presume the purple colour
is the result of reaction with light, air or both (god I hate aniline). If someone could check merk index or simular for confirmation that would be
great, I only have the 6th edition (1952) in which it is not listed. I would have expected if it were strongly coloured, it would be noted as such in
the articles.
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JohnWW
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That purple color sounds as if it is due to formation of an "aniline dye", rather than trichloroaniline. This happens when aniline (or its
derivatives) molecules condense together so as to form aromatic secondary and tertiary amines and sometimes aromatic quaternary ammonium salts, often
with N atoms in aromatic rings. This was first found to happen with the discovery of "Perkins' mauve" in 1856, by the attempted oxidation of aniline
with dichromate and then methanol extraction.
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Nicodem
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Chloroanilines are, like all anilines, of all colors since the slightest oxidation byproducts highly color them (well, generally they get darker
colors if not completely black).
The slightest presence of H2O during the chlorination of aniline will cause the formation of oxidation products. However, P2O5 is not a particularly
good idea to use during the reaction since it reacts with aniline itself.
Axt, you should try the chloroform/Cl2 method again but drying the reaction solution with molecular sieves before introducing Cl2. Also try
recrystallizing the crapy product you got by discoloring with active charcoal. I guess you can use ethanol or isopropanol for the recrystallization,
but I'm not sure.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Axt
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I dont have molecular sieves nor activated charcoal. I did try again yesterday, I dried a solution of aniline-chlorobenzene with P2O5, let it settle
and decanted. HCl gas was bubbled through which resulted in a thick mud-like suspension. Cl2 was bubbled through at 90 degrees (according to
US4447647), the precipitated HCl waslt eventually went into solution after 2 hr. This was then washed with water, HCl, then water again to leave a
brown organic layer. Extracting this and evaporating at 80 degrees resulted in a mush of dark near black purple crystals in a viscous liquid. Yield
was low, so I'll look at routes around aniline itself.
Since the target was to form 1,3,5-trichloro-2,4-dinitrobenzene, I'll instead look at chlorinating m-nitroaniline which should be more forgiving.. and
just as easily produced as aniline.
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Per
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When Aniline could be chlorinated directly with Cl2,
then could 2,4,6-trichlorophenol also be obtained by chlorination
of Phenol in ice water by bubbling Cl2 through?
I red this some time ago but the author wasn´t sure if it works,
so I didn´t tried it.
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MagicJigPipe
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Phenol can be chlorinated by Cl2. In water, I'm not sure. Some aromatics that are less reactive require a lewis acid as a catalyst. Phenol
shouldn't need it though.
Found this:
http://pubs.acs.org/cgi-bin/abstract.cgi/esthag/2005/39/i13/...
A quote from some 2,6-Dichlorophenol MSDS:
"CHLORINATED PHENOLS CAN BE PRODUCED BY THE CHLORINATION OF PHENOL WITH HYPOCHLORITE IN WATER."
That seems to support the water theory as well. But MSDS is not a great source of information.
BTW, I just by my activated charcoal at Wal-Mart. Is this bad?
P.S. I know those aren't the best references but I'm in a hurry! Hope it helps!
**EDIT**
And here's some surprisingly good info from wikipedia on the reaction mechanism.
http://en.wikipedia.org/wiki/Electrophilic_halogenation
[Edited on 17-12-2007 by MagicJigPipe]
"There must be no barriers to freedom of inquiry ... There is no place for dogma in science. The scientist is free, and must be free to ask any
question, to doubt any assertion, to seek for any evidence, to correct any errors. ... We know that the only way to avoid error is to detect it and
that the only way to detect it is to be free to inquire. And we know that as long as men are free to ask what they must, free to say what they think,
free to think what they will, freedom can never be lost, and science can never regress." -J. Robert Oppenheimer
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