# Troubleshooting synthesis of halazone from dichloramine-T

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.

### 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.
• Does your mother liquor have the chlorine odour? Jun 3 at 6:25
• @Waylander Yes and it smells bloody awful Jun 3 at 9:01
• Have you checked the pH of the ML that you are trying to precipitate from? Jun 3 at 9:55
• @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 Jun 3 at 14:13
• Can you concentrate down an aliquot and get an NMR of the residue? Jun 3 at 19:19