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I was trying to oxidize some dichloramine-T to halazone. It should be easy enough since dichloramine-T has a free methyl group para to the para-sulfomyldichloro group. I followed a published procedure [1], but got very different results.

By oxidation of easily available dichloramine-T (3) with $\ce{KMnO4}$ in mild alkaline medium, we have been able to obtain as high as $95\,\%$ halazone containing $18-20\,\%$ chlorine. In this procedure, the sodium salt of halazone (4) is formed in the first step which, after hydrolysis with dilute $\ce{AcOH},$ gives a white crystalline compound with a chlorine odor, melting at $\pu{196 °C}$ with decomposition.

Dichloramine-T to sodium salt of halazone

Experimental

In a $\pu{250 ml}$ flask, $\ce{KMnO4}$ $(\pu{2.9 g})$ was placed and dissolved in water $(\pu{150 ml}).$ Dichloramine-T $(\pu{2.5 g})$ and $\ce{Na2CO3}$ $(\pu{5 g})$ were mixed and added to the flask and stirred for $\pu{5 min}.$ The reaction mixture was refluxed on a steam bath until the dark violet color disappeared $(\pu{2 h}).$ The mixture was then cooled at $\pu{25 °C}$ and filtered. A dark brown precipitate was separated $(\ce{MnO2}).$ The filtrate was yellowish with a chlorine odor which was concentrated and later neutralized with $\ce{AcOH}$ $(50\,\%).$ While neutralizing the solution, a vigorous reaction occurred and a white substance precipitated which was filtered and dried. Yield $95\,\%,$ m.p. $\pu{195-196 °C}.$ This compound was identified as N,N-dichlorosulfamoylbenzoic acid by direct comparison (ir, mass, m.m.p.) with an authentic sample.

My two main problems are:

  1. I can't precipitate the product out of the solution as mentioned. My mother liquor stays colorless and no precipitation occurs upon acidification.
  2. I can't separate the $\ce{MnO2}$ particles from the solution using normal methods like filter papers/cloth and have to use Hyflo® Super Cel® filter aid each and every time.

I've used chromic acid, chromyl chloride, $\ce{KMnO4},$ $\ce{H2O2}$ all to try and oxidize the compound with no avail. Really need some help with this.

Reference

  1. Saljoughian, M.; Sadeghi, M. T. An improved procedure for the synthesis of p-(dichlorosulfamoyl)benzoic acid (halazone). Monatsh Chem 1986, 117 (4), 553–555. DOI: 10.1007/BF00810903.
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    $\begingroup$ Does your mother liquor have the chlorine odour? $\endgroup$
    – Waylander
    Jun 3 at 6:25
  • 2
    $\begingroup$ @Waylander Yes and it smells bloody awful $\endgroup$ Jun 3 at 9:01
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    $\begingroup$ Have you checked the pH of the ML that you are trying to precipitate from? $\endgroup$
    – Waylander
    Jun 3 at 9:55
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    $\begingroup$ @Waylander Yep. Its about 11.85-12.05. Everything checks out. I did the same reaction but I oxidized para toluene sulfonamide instead of Dichloramine T everything else (amount of reagents etc) being the same and I isolated the oxidized para sulfamoyl benzoic acid with about 70% yield. I just can't seem to oxidize Dichloramine T $\endgroup$ Jun 3 at 14:13
  • $\begingroup$ Can you concentrate down an aliquot and get an NMR of the residue? $\endgroup$
    – Waylander
    Jun 3 at 19:19

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