Carbamates, or urethanes, are a group of organic compounds sharing a common functional group with the general structure -NH(CO)O-. Carbamates are esters of carbamic acid, NH2COOH, an unstable compound. Since carbamic acid contains a nitrogen attached to a carboxyl group, it is also an amide. Therefore, carbamate esters may have alkyl or aryl groups substituted on the nitrogen, or the amide function. For example, urethane or ethyl carbamate, is unsubstituted, whereas ethyl N–methylcarbamate has a methyl group attached to the nitrogen (see methyl isocyanate for formation of N-methylcarbamates).

Carbamates in biochemistry

A nitrogen-substituted carbamic acid is formed when a carbon dioxide molecule reacts with the amino terminus of a peptide chain or an amino group of an amino acid, adding a COO group to it and releasing a cation (H+ ion) to form a carbamate ion.

"R" stands for the atoms attached to the other end of the nitrogen atom of the amino group. Note that the COO group is a resonance structure, so the single bonds both show a degree of double-bond character, and the charge is delocalised over the two oxygen atoms. This reaction is reversible (with equilibrium constant "K" << 1 in the above reaction), as the N–C bond is highly labile.

ome occurrences of carbamate groups in nature

In hemoglobin, carbamate groups are formed when carbon dioxide molecules bond with the amino termini of the globin chains. This helps to stabilize the protein when it becomes deoxyhemoglobin and increases the likelihood of the release of remaining oxygen molecules bound to the protein.

Ribulose 1,5-bisphosphate carboxylase/oxygenase (the enzyme required to fix a carbon dioxide molecule at the start of the Calvin cycle) also requires the formation of a carbamate to function. At the active site of the enzyme, a Mg2+ ion is bound to a glutamate residue, an aspartate residue and a lysine carbamate, which hold the ion in place. The carbamate is formed when an uncharged lysine side-chain near the ion reacts with a carbon dioxide molecule from the air (not the substrate carbon dioxide molecule), which then renders it charged, and, therefore, able to bind the Mg2+ ion.

Commercial carbamate compounds

A group of insecticides also contains the carbamate functional group, for example, Aldicarb, Carbofuran, Furadan, Fenoxycarb, Carbaryl, Sevin, Ethienocarb, and 2-(1-Methylpropyl)phenyl N-methylcarbamate. These insecticides can cause cholinesterase inhibition poisoning by reversibly inactivating the enzyme acetylcholinesterase. The organophosphate pesticides also inhibit this enzyme, though irreversibly, and cause a more severe form of cholinergic poisoning.

Polyurethanes contain multiple carbamate groups as part of their structure, but urethane is not a component of polyurethanes. These polymers have a wide range of properties and are commercially available as foams, elastomers, and solids.

Urethane or ethyl carbamate is occasionally used as a veterinary medicine.

In addition, some carbamates are used in human pharmacotherapy, for example, the cholinesterase inhibitors neostigmine and rivastigmine, whose chemical structure is based on the natural alkaloid physostigmine. Other examples are meprobamate and its derivatives, a class of anxiolytic drugs widely used in the 60s before the rise of benzodiazepines, and still used nowadays in some cases.

The insect repellent icaridin is a substituted carbamate.

ee also

*Methyl carbamate
*2-(1-Methylpropyl)phenyl methylcarbamate

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  • carbamate — [ karbamat ] n. m. • 1868; de carbam(ide) « urée » et suff. chim. ate ♦ Chim. Sel ou ester (NH2 COOH) du monoacide de l acide carbonique (acide carbamique), monoacide qui n existe pas à l état libre. ● carbamate nom masculin Sel ou ester de l… …   Encyclopédie Universelle

  • carbamate — [kär′bə māt΄; ] also [, kär bam′āt΄] n. a salt or ester of carbamic acid …   English World dictionary

  • Carbamate — Allgemeine Struktur der Carbamate. Dabei sind: R1 und R2 = Aliphatischer oder aromatischer Rest oder H R3 = Aliphatischer oder aromatischer Rest, H, Metall (bei Salzen) Carbamate sind Salze und Ester der Carbamidsäuren (R2N–COOH) …   Deutsch Wikipedia

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  • carbamate — 1. A salt or ester of carbamic acid forming the basis of urethane hypnotics. 2. A group of cholinesterase inhibiting insecticides resembling organophosphates; the most frequent c. is carbaril. SYN: carbamoate, carbaril. c. kinase a… …   Medical dictionary

  • carbamate — karbamatas statusas T sritis chemija formulė H₂NCOO(M,R) atitikmenys: angl. carbamate; urethane rus. карбамат; уретан …   Chemijos terminų aiškinamasis žodynas

  • Carbamate d'éthyle — Carbamate Les carbamates ou uréthanes sont une famille de composés organiques porteur d une fonction R N (C=O)O R . Il s agit en fait des esters substitués de l acide carbamique ou d un amide substitué. Structure générale des carbamates Sommaire …   Wikipédia en Français

  • Carbamate kinase — In enzymology, a carbamate kinase (EC number| is an enzyme that catalyzes the chemical reaction:ATP + NH3 + CO2 ightleftharpoons ADP + carbamoyl phosphateThe 3 substrates of this enzyme are ATP, NH3, and CO2, whereas its two products are… …   Wikipedia

  • carbamate poisoning — poisoning by exposure to excessive amounts of carbamate insecticides; characteristics include salivation, tremors, dyspnea, and occasionally convulsions. See table at carbamate …   Medical dictionary

  • carbamate — noun Date: 1888 a salt or ester of carbamic acid; especially one that is a synthetic organic insecticide …   New Collegiate Dictionary

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