Chloroacetaldehyde is an

organic compound In chemistry, organic compounds are generally any chemical compounds that contain carbon-hydrogen or carbon-carbon bonds. Due to carbon's ability to catenate (form chains with other carbon atoms), millions of organic compounds are known. T ...

with the formula ClCH₂CHO. Like some related compounds, it is highly electrophilic reagent and a potentially dangerous

alkylating agent Alkylation is the transfer of an alkyl group from one molecule to another. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effectin ...

. The compound is not normally encountered in the anhydrous form, but rather as the

hemiacetal A hemiacetal or a hemiketal has the general formula R1R2C(OH)OR, where R1 or R2 is hydrogen or an organic substituent. They generally result from the addition of an alcohol to an aldehyde or a ketone, although the latter are sometimes called hemi ...

(ClCH₂CH(OH))₂O. Chloroacetaldehyde is a useful intermediate in the synthesis of 2-aminothiazole including the pharmaceuticals altizide, polythiazide, brotizolam and ciclotizolam. Another use is to facilitate bark removal from tree trunks. Chloroacetaldehyde is a metabolite of the antineoplastic

ifosfamide Ifosfamide (IFO), sold under the brand name Ifex among others, is a chemotherapy medication used to treat a number of types of cancer. This includes testicular cancer, soft tissue sarcoma, osteosarcoma, bladder cancer, small cell lung cancer, ...

and believed to be responsible for some of the toxicity observed with ifosfamide.

Synthesis and reactions

Hydrated chloroacetaldehyde is produced by the

chlorination Chlorination may refer to: * Chlorination reaction In chemistry, halogenation is a chemical reaction that entails the introduction of one or more halogens into a compound. Halide-containing compounds are pervasive, making this type of transform ...

of aqueous

vinyl chloride Vinyl chloride is an organochloride with the formula H2C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC ...

: :ClCH=CH₂ + Cl₂ + H₂O → ClCH₂CHO + 2 HCl It can also be prepared from

vinyl acetate Vinyl acetate is an organic compound with the formula CH3CO2CH=CH2. This colorless liquid is the precursor to polyvinyl acetate and ethene-vinyl acetate copolymers, important industrial polymers. Production The worldwide production capacity of v ...

or by careful chlorination of acetaldehyde. The related bromoacetaldehyde is prepared via bromination of

. It also rapidly forms an acetals in the presence of alcohols. Being bifunctional, chloroacetaldehyde is a versatile precursor to many heterocyclic compounds. It condenses with

thiourea Thiourea () is an organosulfur compound with the formula and the structure . It is structurally similar to urea (), except that the oxygen atom is replaced by a sulfur atom (as implied by the ''thio-'' prefix); however, the properties of urea a ...

derivatives to give aminothiazoles. This reaction was important as a precursor to sulfathiazole, one of the first sulfa drugs.

Anhydrous

Water free chloroacetaldehyde is prepared from the hydrate by

azeotropic distillation In chemistry, azeotropic distillation is any of a range of techniques used to break an azeotrope in distillation. In chemical engineering, ''azeotropic distillation'' usually refers to the specific technique of adding another component to gener ...

with chloroform,

toluene Toluene (), also known as toluol (), is a substituted aromatic hydrocarbon. It is a colorless, water-insoluble liquid with the smell associated with paint thinners. It is a mono-substituted benzene derivative, consisting of a methyl group (CH3) a ...

or carbon tetrachloride. Anhydrous chloroacetaldehyde reversibly converts to polyacetals. Less reactive chloroacetaldehyde derivatives might be used instead to obtain chloroacetaldehyde or bypass its intermediate formation completely: e.g. chloroacetaldehyde dimethyl acetal (2-chloro-1,1-dimethoxyethane) hydrolyzes in acidic conditions to give chloroacetaldehyde, which may then quickly react with the other reagents instead of polymerizing.

Hemihydrate

Hemihydrate is formed as below. It has a melting point of 43–50 °C, boiling point of 85.5 °C. Chloroacetaldehyde reaction01

Environmental aspects

Chloroacetaldehyde is a metabolite in the degradation of

1,2-dichloroethane The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon. It is a colourless liquid with a chloroform-like odour. The most common use of 1,2-dichloroethane is in the production of vin ...

, which initially converts to chloroethanol. This metabolic pathway is topical because 1,2-dichloroethane is produced on a large as a precursor to

Safety

Chloroacetaldehyde is corrosive to

mucous membrane A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It i ...

s. It irritates eyes, skin and respiratory tract. Based on data collected from human studies in 1962, exposures to 45 ppm of chloroacetaldehyde were found to be disagreeable and caused conjunctival irritation to the subjects. The

Occupational Safety and Health Administration The Occupational Safety and Health Administration'' (OSHA ) is a large regulatory agency of the United States Department of Labor that originally had federal visitorial powers to inspect and examine workplaces. Congress established the agenc ...

established a

permissible exposure limit The permissible exposure limit (PEL or OSHA PEL) is a legal limit in the United States for exposure of an employee to a chemical substance or physical agent such as high level noise. Permissible exposure limits are established by the Occupational ...

at a ceiling of 1 ppm (3 mg/m³) for exposures to chloroacetaldehyde.CDC - NIOSH Pocket Guide to Chemical Hazards
/ref>

References

{{reflist Aldehydes Organochlorides