Monochloroacetic Acid: Applications and Production Methods
Author : Sneha Biswal | Published On : 26 Mar 2024
Chemical Properties of Monochloroacetic Acid
Monochloroacetic acid (MCAA) is a haloacetic acid with the chemical formula CH2ClCO2H. As its name suggests, it contains one chlorine atom bonded to the methyl carbon. Some key chemical properties of MCAA include:
- It is a clear, colorless liquid at room temperature with a pungent, acidic odor.
- Monochloroacetic Acid is soluble in water, alcohols, ethers, and other polar organic solvents. It has a density of 1.44 g/cm3.
- Its melting point is 53°C and boiling point is 205°C.
- MCAA is a strong acid, with a pKa of 2.86. It ionizes completely in water to produce hydronium and chloroacetate ions.
- Being a haloacetic acid, MCAA can alkylate biomolecules through nucleophilic substitution reactions. This property underlies many of its industrial applications.
Uses and Applications of Monochloroacetic Acid
By far the largest use of MCAA is in the production of glyphosate, the active ingredient in herbicides like Roundup. During the manufacturing process, MCAA alkylates glyphosate to improve its herbicidal activity. Worldwide demand for glyphosate herbicides has made MCAA a multimillion ton commodity chemical.
Other major applications of MCAA include:
- Production of carboxymethyl cellulose (CMC), a thickening and stabilizing agent used in foods, cosmetics, detergents etc. MCAA carboxymethylates cellulose fibers.
- Synthesis of cyromazine, an insecticide/acaricide used in agriculture and veterinary medicine.
- Production of thioglycolic acid, a building block chemical and hair permanent wave agent.
- Chelating agent in laundry detergents and cleaning products due to its ability to bind calcium, magnesium and iron ions.
- Intermediate in the manufacture of dyes, pharmaceuticals, other agrochemicals and surfactants.
Production Methods for Monochloroacetic Acid
There are three main commercial methods used for producing MCAA on an industrial scale:
1. Chlorination of Acetic Acid: Acetic acid is treated with chlorine gas in the presence of a catalyst like mercuric acetate or aluminum chloride. This substitution reaction yields MCAA in over 80% purity.
2. Hydrolysis of Dichloroethane: Dichloroethane produced from ethylene is reacted with base (NaOH) in a hydrolysis reaction to yield MCAA. This process gives higher yields compared to direct chlorination.
3. Oxidative Carbonylation: Trichloroethylene or tetrachloroethylene undergoes oxidative carbonylation in the presence of air/oxygen, carbon monoxide and a copper catalyst. This newer method produces MCAA at high conversions and selectivity.
Global Production and Market Trends
The global production capacity for MCAA currently stands around 2 million tons annually. China dominates manufacturing with over 60% share, followed by the USA, Europe and other Asian countries.
Demand has risen steadily at 4-5% per year tracking glyphosate herbicide sales, which in turn correlates with growth in genetically modified crops. North America and Western Europe are the largest and highest value consuming regions presently.
Due toMCAA’s wide industrial utility, stable market chains have been established ensuring continuity of supply. Growing agricultural output in developing nations is projected to further lift global MCAA consumption over the coming decade.
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