Carbamic acid, which might also be called aminoformic acid or aminocarboxylic acid, is the

chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...

with the formula . It can be obtained by the reaction of

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

and

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

at very low temperatures, which also yields an equal amount of

ammonium carbamate Ammonium carbamate is a chemical compound with the formula consisting of ammonium cation and carbamate anion . It is a white solid that is extremely soluble in water, less so in alcohol. Ammonium carbamate can be formed by the reaction of ammo ...

. The compound is stable only up to about 250 K (−23 °C); at higher temperatures it decomposes into those two gases. The solid apparently consists of

dimer Dimer may refer to: * Dimer (chemistry), a chemical structure formed from two similar sub-units ** Protein dimer, a protein quaternary structure ** d-dimer * Dimer model, an item in statistical mechanics, based on ''domino tiling'' * Julius Dimer ...

s, with the two molecules connected by hydrogen bonds between the two

carboxyl In organic chemistry, a carboxylic acid is an organic acid that contains a carboxyl group () attached to an R-group. The general formula of a carboxylic acid is or , with R referring to the alkyl, alkenyl, aryl, or other group. Carboxylic ...

groups –COOH.J. B. Bossa, P. Theulé, F. Duvernay, F. Borget and T. Chiavassa (2008): "Carbamic acid and carbamate formation in NH₃:CO₂ ices – UV irradiation versus thermal processes". ''Astronomy and Astrophysics'', volume 492, issue 3, pages 719-724. Carbamic acid could be seen as both an

amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen Hydrogen is the chemical element wi ...

and carboxylic acid, and therefore an

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha a ...

;R. K. Khanna and M. H. Moore (1999): "Carbamic acid: molecular structure and IR spectra". ''Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy'', volume 55, issue 5, pages 961-967. however, the attachment of the carboxyl group –COOH directly to the nitrogen atom (without any intermediate carbon chain) makes it behave very differently from the amino acids with intermediate carbon chain. (

Glycine Glycine (symbol Gly or G; ) is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid ( carbamic acid is unstable), with the chemical formula NH2‐ CH2‐ COOH. Glycine is one of the proteinog ...

is generally considered to be the simplest amino acid.) The

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

group –OH attached to the carbon also excludes it from the

amide In organic chemistry, an amide, also known as an organic amide or a carboxamide, is a compound with the general formula , where R, R', and R″ represent organic groups or hydrogen atoms. The amide group is called a peptide bond when it i ...

class. The term "carbamic acid" is also used generically for any compounds of the form RR′NCOOH, where R and R′ are organic

group A group is a number of persons or things that are located, gathered, or classed together. Groups of people * Cultural group, a group whose members share the same cultural identity * Ethnic group, a group whose members share the same ethnic ide ...

s or hydrogen. Deprotonation of a carbamic acid yields a carbamate anion , the salts of which can be relatively stable. Carbamate is also a term used for

ester In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...

s of carbamic acids, such as

methyl carbamate Methyl carbamate (also called methylurethane, or urethylane) is an organic compound and the simplest ester of carbamic acid (H2NCO2H). It is a colourless solid. Methyl carbamate is prepared by the reaction of methanol and urea: :CO(NH2)2 + CH3O ...

. The carbamoyl

functional group In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the re ...

RR′N–C(=O)– (often denoted by Cbm) is the carbamic acid molecule minus the OH part of the carboxyl.

Structure

Carbamic acid is a planar molecule. The group of carbamic acid, unlike that of most amines, cannot be

protonated In chemistry, protonation (or hydronation) is the adding of a proton (or hydron, or hydrogen cation), (H+) to an atom, molecule, or ion, forming a conjugate acid. (The complementary process, when a proton is removed from a Brønsted–Lowry acid, ...

to an ammonium group . The

zwitterionic In chemistry, a zwitterion ( ; ), also called an inner salt or dipolar ion, is a molecule that contains an equal number of positively- and negatively-charged functional groups. : With amino acids, for example, in solution a chemical equilibrium wil ...

form is very unstable and promptly decomposes into ammonia and carbon dioxide,Y.-J. Chen, M. Nuevo, J.-M. Hsieh, T.-S. Yih, W.-H. Sun, W.-H. Ip, H.-S. Fung, S.-Y. Chiang, Y.-Y. Lee, J.-M. Chen and C.-Y. R. Wu (2007): "Carbamic acid produced by the UV/EUV irradiation of interstellar ice analogs". ''Astronomy and Astrophysics'', volume 464, issue 1, pages 253-257. yet there is a report of its detection in ices irradiated with high-energy protons.

Derivatives

Carbamic acid is formally the parent compound of several important families of organic compounds: File:Carbamic-acid-group-2D-L.png, carbamic acids File:Carbamate-anion-generic-2D.png, carbamate anions File:Carbamate-group-2D.png, carbamate esters File:Carbamoyl-chloride-generic-2D.png,

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 orga ...

Carbamic acids

Many substituted carbamic acids (RHNCOOH or RR′NCOOH), can be readily synthesized by bubbling carbon dioxide through solutions of the corresponding amine ( or RR′NH, respectively) in an appropriate solvent, such as

DMSO Dimethyl sulfoxide (DMSO) is an organosulfur compound with the formula ( CH3)2. This colorless liquid is the sulfoxide most widely used commercially. It is an important polar aprotic solvent that dissolves both polar and nonpolar compounds ...

or supercritical carbon dioxide.Z. J. Dijkstra, A. R. Doornbos, H. Weyten, J. M. Ernsting, C. J. Elsevier, and J. T. F. Keurentjes (2007): "Formation of carbamic acid in organic solvents and in supercritical carbon dioxide". ''Journal of Supercritical Fluids'', volume 41, issue 1, pages 109-114. These carbamic acids are generally unstable at room temperature, reverting to the parent amine and carbon dioxide.

Carbamate esters

Unlike carbamic acids, carbamate esters are generally stable at room temperature. They are prepared by reaction of

s with alcohols, the addition of alcohols to

isocyanate In organic chemistry, isocyanate is the functional group with the formula . Organic compounds that contain an isocyanate group are referred to as isocyanates. An organic compound with two isocyanate groups is known as a diisocyanate. Diisocyan ...

s, and the reaction of carbonate esters with ammonia.

Methyl carbamate Methyl carbamate (also called methylurethane, or urethylane) is an organic compound and the simplest ester of carbamic acid (H2NCO2H). It is a colourless solid. Methyl carbamate is prepared by the reaction of methanol and urea: :CO(NH2)2 + CH3O ...

and

ethyl carbamate Ethyl carbamate (also called urethane) is an organic compound with the formula CH3CH2OC(O)NH2. It is an ester of carbamic acid and a white solid. Despite its name, it is not a component of polyurethanes. Because it is a carcinogen, it is rarely us ...

are among the simplest examples and have historically been used in the textile industry, both are now suspected carcinogens. Benzyl carbamate is also known.

Occurrence in nature

The

enzyme Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products ...

carbamate kinase, involved in several metabolic pathways of living organisms, catalyzes the formation of

carbamoyl phosphate Carbamoyl phosphate is an anion of biochemical significance. In land-dwelling animals, it is an intermediary metabolite in nitrogen disposal through the urea cycle and the synthesis of pyrimidines. Its enzymatic counterpart, carbamoyl phosphate sy ...

: : One

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyt ...

molecule can carry four molecules of carbon dioxide to the lungs as carbamate groups formed by reaction of with four terminal amine groups of the deoxy form. The resulting compound is called carbaminohaemoglobin.

Uses

Industrial

Carbamic acid is an intermediate in the industrial production of urea, which involves the reaction of carbon dioxide and ammonia. : :

Medical

Some carbamate esters have use as

muscle relaxant A muscle relaxant is a drug that affects skeletal muscle function and decreases the muscle tone. It may be used to alleviate symptoms such as muscle spasms, pain, and hyperreflexia. The term "muscle relaxant" is used to refer to two major therap ...

s, including

Emylcamate Emylcamate (marketed as Striatran by Merck) is an anxiolytic and muscle relaxant. It was patented in the US in 1961 (US Patent 2,972,564) and advertised for the treatment of anxiety and tension. It was claimed to be superior to meprobamate Me ...

Phenprobamate Phenprobamate (Gamaquil, Isotonil) is a centrally acting skeletal muscle relaxant, with additional sedative and anticonvulsant effects. Overdose is similar to barbiturates. Its mechanism of action is probably similar to meprobamate. Phenproba ...

Styramate Styramate is a muscle relaxant and anticonvulsant drug. At therapeutic doses, it does not produce significant sedative effects. See also * Carisbamate Carisbamate (YKP 509, proposed trade name Comfyde) is an experimental anticonvulsant drug ...

and other members of ATC code M03BA. These bind to the barbiturate site of the GABA_A receptor.

Insecticides

Several carbamic acid based insecticides have been developed; for example

aldicarb Aldicarb is a carbamate insecticide which is the active substance in the pesticide Temik. It is effective against thrips, aphids, spider mites, lygus, fleahoppers, and leafminers, but is primarily used as a nematicide. Aldicarb is a cholinester ...

carbaryl Carbaryl (1-naphthyl methylcarbamate) is a chemical in the carbamate family used chiefly as an insecticide. It is a white crystalline solid previously sold under the brand name Sevin, which was a trademark of the Bayer Company. The Sevin trademark ...

carbofuran Carbofuran is a carbamate pesticide, widely used around the world to control insects on a wide variety of field crops, including potatoes, corn and soybeans. It is a systemic insecticide, which means that the plant absorbs it through the r ...

Chemical synthesis

An amine functional group can be

protected Protection is any measure taken to guard a thing against damage caused by outside forces. Protection can be provided to physical objects, including organisms, to systems, and to intangible things like civil and political rights. Although th ...

from unwanted reactions by being formed as carbamate ester

residue Residue may refer to: Chemistry and biology * An amino acid, within a peptide chain * Crop residue, materials left after agricultural processes * Pesticide residue, refers to the pesticides that may remain on or in food after they are applied ...

–NHC(=O)–OR.

Hydrolysis Hydrolysis (; ) is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile. Biological hydrolys ...

of the

ester bond In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...

then produces a carbamic acid –NHC(=O)OH, which then loses carbon dioxide yielding the desired amine.

References

{{DEFAULTSORT:Carbamic Acid Carbamates