Sciencemadness Discussion Board

S-Isopropylisothiouronium bromide

myr - 6-8-2018 at 06:55

I would like to present my preliminary findings, and ask for further advice.

S-Isopropylisothiouronium bromide was prepared by the reaction of isopropyl bromide (crude, distilled from 70& isopropanol, sulfuric acid and NaBr) and thiourea in 95% denatured ethanol (purchased from Duda Diesel) and thiourea

To a roundbotom flask with magnetic stirring was added 25mL denatured ethanol, 4g thiourea (~53mmol) and 6.6g isopropyl bromide (crude) (approx. equimolar). The flask was held at reflux using a liebig condensor for 4h, at which point everything had dissolved. Leaving to cool overnight, the solution crystallized to deposit white needles. When the flask warmed (due to daytime temperatures outside) a substantial portion redissolved. The round-bottom was placed in a freezer, which caused the crystallization of fine white needles- which are drying on the filter ATM.

Adding a small portion to aq. KOH was a strong positive for the presence of the isothiouronium salt, and rather distressing.

I would like to chlorinate this salt to give the isopropylsulfonyl chloride for the preparation of various alkylating agents. Does anyone have any experience with this kind of reaction?

Reference (a similar salt is prepared as an intermediate):

"In a round-bottomed flask, 1 mole of 2-butyl bromide or 2-butyl chloride (or 1/2 mole of 2-dibutyl sulfate) is added to 1.1 mole of thiourea and 50 ml of 95% alcohol, and the mixture is refluxed for 6 hours. On cooling, the 2-butylthiouronium salt crystallizes out. It is filtered off and is hydrolysed to the butyl thiol without further purification by treating 1 mole of the butyl thiouronium salt (in the case of a thiouronium sulfate only 1/2 mole) in a two-necked flask with 300 ml of 5 N caustic sodium carbonate and the mixture is refluxed in a slow current of nitrogen for 2 hours. The cooled reaction mixture is acidified with 2 N hydrochloric acid; the butyl thiol layer is separated off and dried with the anhydrous magnesium sulfate and the product is fractionated through a Vigreux column b.p. 85°C, nD=1338. The yield of 2-butanethiol is 60%."

Organicum. Practical Handbook of Organic Chemistry, by Heinz Becker, Werner Berger and Günter Domschke, Addison-Wesley Pub. Co, 217-218, (1973)

JacobM - 15-1-2022 at 05:58

This is definitely an interesting piece of work here.

AvBaeyer - 15-1-2022 at 19:39

At the risk of sounding snarky, you should learn how to search such things on google (eg "sulfonyl chlorides from isothiouronium salt"). One old and general method of converting isothiouronium salts to sulfonyl chlorides is with chlorine (eg Another is with N-chlorosuccinimide ( Given the latter reference, TCCA or NaDCCA should also work. There might well be references for these reagents in this type of reaction if you search.

I am not picking on you only but there are far too many questions asked here that could be easily answered by learning how to effectively use google and google scholar. Chemistry is an extremely well documented and indexed science that can readily be interrogated by anyone with commonly available resources.

My apologies in advance to anyone who is herewith offended.


myr - 29-1-2022 at 05:14

I was able to purchase tosyl chloride, so there was no need for any chlorination.

It was about 5 years ago, but my intended goal in asking if anyone had any experience in the reaction was for advice on what pitfalls they encountered etc, or even as just an invitation to further discussion.

crow6283 - 29-1-2022 at 09:04

@myr I said S-Isopropylisothiouronium bromide THREE times fast before it all went to pieces have you attempted this, and if so could you share your results ??