guy
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Tillman's Reagent (2,6-dichloroindophenol) synth help
The reaction of phenol, hypochlorite, and ammonia is used to test for ammonia. It forms a blue solution in the presence of ammonia which is the
indophenol. This compound is also a useful indicator for measuring the rate of photosynthesis.
I tested this and it easily forms a clear blue-green solution. The question is how pure is this product? Are there any side reactions?
edit:
I actually used salicylic acid instead of phenol, but the results are similar. When forming a quinone, does decarboxylation take place??
Hmm apparently the reaction needs a nitroprusside catalyst, but I didnt use one. My product was green-blue but very interestingly it turned bright
red after a few minutes.
It must have been a different compound....
[Edited on 9/26/2007 by guy]
[Edited on 9/26/2007 by guy]
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not_important
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| Quote: | The Salicylate Method
References: Krom, Michael D., Spectrophotometric
Determination of Ammonia: A Study of a Modified
Berthelot Reduction Using Salicylate and
Dichloroisocyanurate, The Analyst, V105, pp. 305-316,
1980.
In the ammonia test method that employs the Salicylate
chemistry, free ammonia reacts with hypochlorite to
form monochloramine. Monochloramine reacts with
salicylate, in the presence of sodium nitro-ferricyanide,
to form 5-aminosalicylate, a green-colored complex.
This test method measures free ammonia and mono-
chloramine. |
Elsewhere the colour is given as being from yellow, for traces of ammonia, to green and then blue-green as the ammonia concentration is increased.
| Quote: | 2. Ammonia and Hypochlorite Test.—If to a solution containing
even so small a quantity as 1 part of carbolic acid in 5000 parts of
water, first, about a quarter of its volume of ammonia hydrate be added,
and then a small quantity of sodic hypochlorite solution, avoiding excess,
a blue colour appears ; warming quickens the reaction : the blue
is permanent, but turns to red with acids. If there is a smaller
quantity than the above proportion of acid, the reaction may be still
produced feebly after standing fur some time. |
| Quote: | Action of Chloride of Benzyl upon Naphthylamin. —
Ch. Froté and D. Tommasi.
Erythrophenic Acid, a New Reaction of Phenol
and Aniline.—E. Jacquemin.—When phenol is treated
with chlorine-water, no reaction is observed, and ammonia
added to the mixture subsequently develops no
colouration. It is known that aniline, on the contrary, suspended in water, with the addition of a solution of chlorine, takes a rose colour, which
rapidly becomes purple, violet, and, lastly, brownish red, and that ammonia added at this last juncture increases the brownness. It is no longer the
same when a mixture of a drop of phenol and a drop of aniline is submitted to the aflion of solution of chlorine. A permanent rose-red is obtained,
which may be turned to a blue either by ammonia or by the alkalies or alkaline carbonates. Acids restore the original redness. The author concludes
that there exists a phenate of phenylamin ; that the new body produced in the above reaction is a red acid, forming blue salts; the erythrophenate of
soda may be produced by causing hypochlorite of soda to aft upon the mixture of phenol and aniline. The blue thus formed is remarkable for its purity
and extraordinary tinftorial power. If two drops of the mixture of phenol and aniline be added to 2 litres of water, and then treated with
hypochlorite, the blue in an hour or two becomes so intense that it could be recognised even in 4 litres of water. This reaction may be useful in
toxicological researches either for aniline or phenol. The purity and permanence of the blue might render it fit for the uses of the dyer, but it will
not bear steaming. The extreme facility with which it is reddened by the feeblest acids is likewise an objeftion. In this re- speft it far exceeds
litmus. |
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guy
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Wow thanks not_important.
Hmm...something weird happened. After I left it over night, it turned GREEN again! It must have been at different stages of the reaction where at one
point it became acidic...
Almost all sources Ive read say that sodium nitroprusside is needed as a catalyst. I guess without the catalyst, it goes through this crazy "cycle".
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guy
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I tried the reaction with Mn2+ as a catalyst and I got a blue solution that quickly turned red. I experimented with it and found that if I diluted it
a little bit, it turns back to green-blue. Must have turned red because it was too alkaline.
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YT2095
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I can confirm the second reaction he quoted too, I used a 1% soln of phenol water and it worked quite nicely.
(yes, it`s a boring day here so I figured I`d search this place for interesting Color chemistry).
\"In a world full of wonders mankind has managed to invent boredom\" - Death
Twinkies don\'t have a shelf life. They have a half-life! -Caine (a friend of mine)
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