Carbamoyl chloride

A carbamoyl chloride is the functional group with the formula R₂NC(O)Cl. The parent carbamoyl chloride, H₂NCOCl is unstable, but many N-substituted analogues are known. Most examples are moisture sensitive, colourless, and soluble in nonpolar organic solvents. An example is dimethylcarbamoyl chloride (m.p. −90 °C and b.p. 93 °C). Carbamoyl chlorides are used to prepare a number of pesticides, e.g. carbofuran and aldicarb.^[1]

Production and examples

Carbamoyl chlorides are prepared by the reaction of an amine with phosgene:

2 R₂NH + COCl₂ → R₂NCOCl + [R₂NH₂]Cl

They also arise by the addition of hydrogen chloride to isocyanates:

RNCO + HCl → RNHCOCl

In this way, carbamonyl chlorides can be prepared with N-H functionality.

Reactions

In a reaction that is typically avoided, hydrolysis of carbamoyl chlorides gives carbamic acids:

R₂NCOCl + H₂O → R₂NC(O)OH + HCl

Owing to the influence of the amino group, these compounds are less hydrolytically sensitive than the usual acid chlorides. A related but more useful reaction if the analogous reaction with alcohols:^[2]

R₂NCOCl + R'OH + C₅H₅N → R₂NC(O)OR' + C₅H₅NHCl

References

1. ↑ Peter Jäger, Costin N. Rentzea and Heinz Kieczka "Carbamates and Carbamoyl Chlorides" in Ullmann's Encyclopedia of Industrial Chemistry, 2012, Wiley-VCH, Weinheim. doi:10.1002/14356007.a05_051
2. ↑ Carol Dallaire, Isabelle Kolber, and Marc Gingras "Nickel-Catalyzed Coupling of Aryl O-Carbamates with Grignard Reagents: 2,7-Dimethylnaphthalene" Org. Synth. 2002, 78, 42. (use of diethylcarbamoyl chloride as protecting and leaving group).