Process for preparation of 5-mercaptotetrazolyl-1-acetic acid

The process for the production of an alkaline solution of 5-mercaptotetrazolyl-1-acetic acid which consists of the consecutive steps of

• (a) heating at a temperature between 50.degree. C. and 100.degree. C. a solution in chloroform or carbon tetrachloride of tetrazolyl-1-acetic acid with enough added acetic acid to bring the tetrazolyl-1-acetic acid into solution and twice as many moles of bromine as of tetrazolyl-1-acetic acid to produce 5-bromotetrazolyl-1-acetic acid,
• (b) precipitating said 5-bromotetrazolyl-1-acetic acid as a solid by addition of a nonsolvent therefor which is a liquid alkane or a mixture of liquid alkanes,
• (c) recovering said solid 5-bromotetrazolyl-1-acetic acid and heating it to reflux in a lower aliphatic alcohol in the presence of an amount of thiourea which is equimolar to the 5-bromotetrazolyl-1-acetic acid and then
• (d) mixing with the resulting mixture dilute, aqueous sodium hydroxide or potassium hydroxide with stirring at room temperature to produce an alkaline solution of 5-mercaptotetrazolyl-1-acetic acid.