Overview

Chloroacetic acid, commonly called monochloroacetic acid (often abbreviated MCA), is an organochlorine derivative of acetic acid in which one hydrogen on the methyl group has been replaced by a chlorine atom. Its molecular formula is C2H3ClO2 and it is a colorless crystalline solid under normal conditions. The substitution of an electron-withdrawing chlorine atom increases the acidity relative to acetic acid and makes the molecule a useful reactive intermediate in organic synthesis.

Chemical characteristics

As a carboxylic acid, chloroacetic acid donates a proton from its –COOH group and is significantly stronger than acetic acid because the chloro substituent stabilizes the conjugate base. It is soluble in water and many polar organic solvents and is commonly encountered as the pure acid or as its salts (for example sodium chloroacetate). Key identifiers include its formula C2H3ClO2 and the structural motif Cl–CH2–COOH.

Production and major uses

Industrially, chloroacetic acid is produced by chlorination of acetic acid followed by purification, or by related halogenation routes. It is an important intermediate in the manufacture of a wide range of products. Notable applications include:

  • Production of carboxymethyl cellulose and other cellulose derivatives via the corresponding chloroacetates.
  • Synthesis of dyes, pigments and specialty chemicals where the chloroacetyl fragment is introduced into molecules; see examples in dye chemistry.
  • Preparation of agrochemicals, pharmaceuticals and surfactants; many active ingredients are built from chloroacetate precursors.
  • Chemical cauterization agents: related acids have been used for topical removal of warts and other lesions in controlled medical settings; consult medical guidance on safe use (wart treatments).

Health, hazards and historical notes

Chloroacetic acid is corrosive and can cause severe chemical burns on contact with skin or eyes; it is also systemically toxic if absorbed, inhaled or ingested. Appropriate personal protective equipment and ventilation are required when handling it in industrial or laboratory settings. The compound's strong corrosive action accounts for historical and military interest in various halogenated acetic derivatives; it is therefore handled as a hazardous substance and regulated in many jurisdictions. For acute exposure risks to skin see safety guidance (skin hazard).

Chloroacetic acid is one member of a family that includes dichloroacetic and trichloroacetic acids. Increasing the number of chlorine atoms generally raises acidity and alters biological and chemical behavior: for example, trichloroacetic acid is a much stronger acid and is used under controlled conditions for certain medical procedures. The parent molecule, acetic acid, lacks the halogen and is far less acidic; the substituent chlorine atom (chlorine) attached in place of a hydrogen (hydrogen atom) is responsible for the majority of chloroacetic acid's distinctive reactivity.

Because of its widespread industrial role and hazardous nature, chloroacetic acid appears in safety data-sheets, regulatory lists and material handling standards. Consult authoritative chemical safety resources for exposure limits, storage recommendations and emergency response procedures (historical and regulatory context).