Among the raw materials and chemical intermediates it is possible to distinguish compounds with a very specific and narrow range of applications. However, some of them have much broader application capabilities. That is why they are used in many different industries. Chloroacetic acid, which is worth looking at a little closer, belongs to the second group.
Monochloroacetic acid (MCAA) is one of the most important intermediates in the chemical industry. Chloroacetic acid is used in numerous organic synthesis processes due to its high reactivity. These include, among other things, manufacturing of plant protection products, fertilizers, plastics, detergents, paints and lacquers, cosmetics and personal hygiene products. Chloroacetic acid is also present in various processes in pulp and paper, pharmaceutical, food and mining industries.
The primary use of MCAA is the manufacture of carboxymethylcellulose (CMC). Up to 30% of the world’s production of monochloroacetic acid is used in that process. This cellulose derivative is used in the manufacture of wallpaper adhesives, detergents, soaps and as emulsion paint thickener. In the production of ceramics it acts as a thickener, plasticizer and binding agent, also improving the smoothness of the enamel. In the food industry carboxymethylcellulose is hidden under the symbol E466. In food production, it is used as a thickener, emulsifier and stabilizer.
Another industry that uses monochloroacetic acid is the agrochemicals industry. It acts as an intermediate in the production of active substances in this industry. They are the main constituents of plant protection products, which are essential for the cultivation of plants such as herbicides or insecticides. With the use of MCAA, the following substances are produced:
– 2,4-D acid (i.e. 2,4-dichlorophenoxyacetic acid),
– thiophosphoric acid esters (e.g. dimethoate),
– chloroacetyl chloride (CAC),
– trichloroacetyl chloride (TCAC),
– 2,4,5-trichlorophenoxyacetic acid (2,4,5-T),
– 2-methyl-4-phenoxyacetic acid (MCPA),
– phosphonates (e.g. glyphosate – the main ingredient of the popular herbicide Roundup).
MCCA also plays a part in the cosmetic and personal hygiene industry as it is used in the production of betaines, that is, amphoteric surfactants having foaming properties, used in hair shampoos. Thioglycolic acid (TGA or mercaptoacetic acid), which is a part of permanent hair styling formulations, is also produced using MCCA.
The specificity of the monochloroacetic acid production means that the end product could contain, as contaminant, some amount of DCAA (dichloroacetic acid). The implementation of an additional purification step allows ultra pure MCCA to be obtained. Thanks to this, it can be used in synthesis processes where exceptionally high quality substrates are required. The result of this is that one of the unique applications of chloroacetic acid is the production of pharmaceuticals, including ibuprofen, diclofenac sodium salt, synthetic caffeine, vitamin B6, glycine and malonates. Moreover, the MCAA derivative, chloroacetyl chloride, is a precursor of adrenaline, also called the stress hormone. Adrenaline is used as a stimulant for cardiac arrest. It is also an antiallergy drug used in anaphylactic shock. MCAA alone may be included in wart removal formulations.
However, the list of possible applications of chloroacetic acid does not end there. In the chemical industry, this compound is an intermediate in the synthesis of indigo dyes and in the processing of polyvinyl chloride as a stabilizer. With the use of MCAA acid, many other chemicals are also produced – coumarin, malonic acid, cyanoacetic acid or EDTA, a known cationic complexing agent.