Monochloroacetic acid (MCA) is a chlorinated carboxylic acid with the chemical formula CH2ClCOOH. As an organic compound, it contains both a carboxyl group as well as a chloromethyl substituent. This unique structure gives MCA a variety of applications both industrially and commercially.
Chemical Properties of MCA
MCA is a colorless, hygroscopic crystalline solid at room temperature. Upon heating, it melts at 189°C and boils at 270°C. In terms of solubility, Monochloroacetic Acid is highly soluble in water, alcohols, ethers and other polar organic solvents but is insoluble in nonpolar solvents like toluene and hexane.
As a weak acid, MCA readily ionizes in aqueous solution to yield the monochloroacetate anion (CH2ClCOO−) and a proton (H+). Its pKa value is 2.86, indicating it is slightly weaker acid than other monosubstituted carboxylic acids like acetic acid and monobromoacetic acid. This property makes it an effective acid scavenger.
The chloromethyl group of MCA participates readily in nucleophilic substitution reactions. Common nucleophiles like hydroxide, ammonia and amines will displace the chloride ion. Additionally, the carboxylic acid group can undergo esterification reactions with alcohols. These reaction pathways are discussed further below.
Herbicide Applications
One of the largest uses of MCA is in the production of the herbicide glyphosate, which is the active ingredient in the widely popular Roundup formulation. Glyphosate is synthesized by reacting MCA with the amino acid glycine. Upon spraying, glyphosate disrupts the shikimate pathway present in plants but not animals, thus selectively killing weeds without harming crops.
Other halogen-substituted monocarboxylic acids such as 2,4-D and dicamba are prepared similarly and employed as selective herbicides. The versatility of MCA’s reactivity has made it a fundamental building block in the agrochemical industry. Herbicides remain a major economic driver for MCA production.
Drug Intermediates
Pharmaceutical companies also utilize MCA as a starting material to synthesize active pharmaceutical ingredients and drug metabolites. Due to its facile substitution, it can be used to introduce chloromethyl groups which are present in many natural products and synthetic drugs.
Some examples include the anti-cancer drugs cyclophosphamide and chlorambucil. Other applications involve synthesizing drug candidates that aim to treat diabetes, arthritis, epilepsy and psychiatric conditions. As drug discovery relies more on medicinal chemistry approaches, the need for versatile building blocks like MCA is increasing.
Surfactants and Emulsifiers
Alkyl monoesters and salts of Monochloroacetic Acid function as anionic surfactants and emulsifiers. Industrially, sodium monochloroacetate is commonly used. It readily forms stable oil-in-water emulsions due to the hydrophilic carboxylate and hydrophobic alkyl chain.
Personal care products take advantage of these amphiphilic properties. Sodium monochloroacetate acts as a cleansing agent in soaps, shampoos and other cleansers. It helps solubilize oils and suspend particulate impurities to rinse them away effectively.
As an emulsifier, it enables the production of lotions, creams and ointments by maintaining a stable dispersion of oil and water phases. Increasing demand for personal care items correlates to growing consumption of MCA-derived surfactants. They remain useful soluble dispersing agents.
Cellulose Derivatives
Cellulose is a polymer of glucose found in the cell walls of plants. It is the most abundant organic material on Earth. While raw cellulose has limited chemical reactivity, reaction with MCA yields water-soluble cellulose derivatives with new industrial applications.
One such product is sodium carboxymethyl cellulose (CMC). When cellulose reacts with MCA in the presence of alkali such as sodium hydroxide, the resulting CMC product has carboxymethyl functional groups (-CH2COONa) randomly attached along the cellulose backbone.
Properties of CMC include thickening, suspending, binding and emulsion stabilizing. Uses range from thickeners in foods, sauces, and ceramics to binders in paper manufacturing, pharmaceutical tablets and cosmetics. CMC production accounts for a significant demand of MCA. Its ability to derivatize natural polymers widens applicability.
Additional Applications
Aside from major markets above, MCA finds various more niche usages. It is sometimes used to control bacterial and fungal infections agriculturally when mixed into fertilizers, compost or soil as a biocide.
Industrially, it enters into the manufacture of other chlorinated hydrocarbons, resins, flocculants, and more. Lastly, analytical chemists take advantage of its acidity and chlorine functionality in organic synthesis as a building block, protecting group or diagnostic reagent like in haloform tests.
Monochloroacetic acid stands out as a commodity chemical with broad commercial importance due to its versatile reactivity pattern. Whether through nucleophilic substitution of its chloride or further transformations of added functional groups, MCA serves as a fundamental building block across agrochemical, pharmaceutical, personal care and other manufacturing
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1. Source: Coherent Market Insights, Public sources, Desk research
2. We have leveraged AI tools to mine information and compile it