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InnoVenton and The Downstream Chemicals Technology Station

Synthesis of Bromochloromethane using phase transfer catalysis


Bromochloromethane (BCM) is a colorless, heavy liquid of low viscosity which is used commercially as a solvent or an intermediate during organic synthesis. BCM is an important intermediate in the synthesis of the fungicide 2-(thiocyanomethyl)-thiobenzothiazole (TCMTB) that is used for controlling the growth of fungi and sulphate-reducing bacteria in the leather industry. Previously, fungal attack in the leather industry was prevented by using pentachlorophenol, but its use is no longer acceptable due to the possibility of the formation of chlorinated dibenzodioxine, a poisonous compound. Substituted benzothiazoles such as (TCMTB) have become the norm.

BCM is also used as a halogenating agent during the synthesis of the microbiocide methylene bisthiocyanate (MBT) in the leather industry. Commercially biocidal formulations containing a blend of 10% MBT and 10% TCMTB are available which combines the rapid antimicrobial action of MBT with the fungal properties of TCMTB. Such biocides are suitable for use over a wide range of tannery applications including the soaking and pickling stages.

The overall objective of the project is to optimize the phase transfer catalyzed reaction of dichloromethane with sodium bromide in a batch pressure reactor, with respect to yield/ reactor throughput.

InnoVenton, NMMU MSc student Mr Lancelot Brooks presented the above paper at the Annual Eastern Province SACI / Pharmacare Post-graduate Chemistry Seminar, which took place on 23 October 2009 at the University of Fort Hare, Alice; Lancelot won third price in this category.

MSc student Mr Lancelot Brooks