Chloroformate

 ( Functional Groups ) 

Chloroformates are a class of with the formula ROC(O)Cl. They are formally of chloroformic acid. Most are colorless, volatile liquids that degrade in moist air. A simple example is methyl chloroformate, which is commercially available.

Chloroformates are used as in organic chemistry. For example, benzyl chloroformate is used to introduce the Cbz (carboxybenzyl) protecting group and fluorenylmethyloxycarbonyl chloride is used to introduce the FMOC protecting group. Chloroformates are popular in the field of chromatography as derivatization agents. They convert polar compounds into less polar more volatile derivatives. In this way, chloroformates enable relatively simple transformation of large array of metabolites (aminoacids, amines, carboxylic acids, phenols) for analysis by gas chromatography / mass spectrometry.

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Reactions The reactivity of chloroformates and are similar. Representative reactions are:

• Reaction with to form :

ROC(O)Cl + H₂NR' → ROC(O)-N(H)R' + HCl

• Reaction with alcohols to form :

ROC(O)Cl + HOR' → ROC(O)-OR' + HCl

• Reaction with to form :

Typically these reactions would be conducted in the presence of a base which serves to absorb the HCl.

Alkyl chloroformate esters degrate to give the alkyl chloride, with retention of configuration:

The reaction is proposed to proceed via a substitution nucleophilic internal mechanism.

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