What is a carbamate group

Carbamates

Carbamates
Carbamate ester - ester of carbamic acid - with the blue labeled carbamate group. The following applies: R1 and R2 are organyl residues (alkyl residues, aryl residues, arylalkyl residues, etc.) or hydrogen atoms. R.3 can be an organyl radical (alkyl radical, aryl radical, arylalkyl radical, etc.).
Carbamate sodium salt - salt of carbamic acid - with the blue labeled carbamate group. The following applies: R1 and R2 are organyl residues (alkyl residues, aryl residues, arylalkyl residues, etc.) or hydrogen atoms. The sodium cation is just one example; other cations can also serve as a counterion to the carbamate anion.

Carbamates are salts and esters of carbamic acids (R2N-COOH). The esters are more common than Urethanes designated. Polyurethanes also belong to the carbamates.

Manufacturing

Carbamates can be prepared from isocyanates and alcohols by an addition reaction, where R1 and R2Organyl groups such as B. Alkyl groups or aryl groups are:[1]


The mostly unstable carbamic acids can be produced from an amine and CO2:

R.2NH + CO2 → R2NCO2H

or by hydrolysis of a chloroformamide:

R.2NC (O) Cl + H2O → R2NCO2H + HCl

properties

Urethanes are mostly solids that crystallize well and are therefore used as identification preparations in chemical analysis.

The toxicity of some carbamates (e.g. Bendiocarb) is the same as that of the phosphoric acid derivatives (phosphoric acid esters) used as pesticides and is based on their neurotoxic effect. Persistence in the environment is 1 to 12 weeks. Carbamates are more stable to hydrolysis than esters.

use

Carbamates have been used primarily as insecticides, fungicides and herbicides in agriculture since the 1950s. The worldwide consumption of carbamates was around 30,000 tons in 1995. Ammonium carbamate is important as an intermediate product in the technical production of urea. Some carbamates were previously used as sleep aids. In organic synthesis, carbamates are used as protective groups for hydroxyl functions because of their stability towards base-catalyzed hydrolysis.

Carbamate-analogous groups of substances with heteroatoms

By replacing one or both oxygen atoms in the molecule, one arrives at the heteroanalogous compounds of the carbamates[2] (R1 to R4 = aliphatic or aromatic radicals or hydrogen).

Individual evidence

  1. ↑ Siegfried Hauptmann: Organic chemistry, VEB German publishing house for basic industry, Leipzig, 1985, p. 325. ISBN 3-342-00280-8.
  2. ↑ Matthys J. Janssen: Thiolo, Thiono, and Dithio Acids and Esters in: The Chemistry of Carboxylic Acids and Their Esters (1969) Chap. 15th