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 was ...

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 transpar ...

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 bond In chemistry, a hydrogen bond (or H-bond) is a primarily electrostatic force of attraction between a hydrogen (H) atom which is covalently bound to a more electronegative "donor" atom or group (Dn), and another electronegative atom bearing a ...

s between the two carboxyl 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 atoms have been replaced by a substituen ...

and

carboxylic acid 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 ...

, 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 am ...

;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 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 hydroxy ...

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 is ...

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

organic Organic may refer to: * Organic, of or relating to an organism, a living entity * Organic, of or relating to an anatomical organ Chemistry * Organic matter, matter that has come from a once-living organism, is capable of decay or is the product ...

groups or hydrogen. Deprotonation of a carbamic acid yields a

carbamate In organic chemistry, a carbamate is a category of organic compounds with the general formula and structure , which are formally derived from carbamic acid (). The term includes organic compounds (e.g., the ester ethyl carbamate), formally o ...

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 ar ...

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 rest ...

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, i ...

to an

ammonium The ammonium cation is a positively-charged polyatomic ion with the chemical formula or . It is formed by the protonation of ammonia (). Ammonium is also a general name for positively charged or protonated substituted amines and quaternary a ...

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

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

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 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 isocyanates, 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 are among the simplest examples and have historically been used in the textile industry, both are now suspected carcinogens.

Benzyl carbamate Benzyl carbamate is the organic compound with the formula C6H5CH2OC(O)NH2. The compound can be viewed as the ester of carbamic acid (O=C(OH)(NH2)) and benzyl alcohol, although it is produced from benzyl chloroformate with ammonia. It is a white ...

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. A ...

carbamate kinase In enzymology, a carbamate kinase () is an enzyme that catalyzes the chemical reaction :ATP + NH3 + CO2 \rightleftharpoons ADP + carbamoyl phosphate The 3 substrates of this enzyme are ATP, NH3, and CO2, whereas its two products are ADP and ...

, involved in several

metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...

pathways of living organisms,

catalyzes Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

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 syn ...

: : 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 (erythrocyte ...

molecule can carry four molecules of carbon dioxide to the

lung The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of t ...

s 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 relaxants, 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 dru ...

and other members of ATC code M03BA. These bind to the

barbiturate Barbiturates are a class of depressant drugs that are chemically derived from barbituric acid. They are effective when used medically as anxiolytics, hypnotics, and anticonvulsants, but have physical and psychological addiction potential as we ...

site of the GABA_A receptor.

Insecticides

Several carbamic acid based

insecticide Insecticides are substances used to kill insects. They include ovicides and larvicides used against insect eggs and larvae, respectively. Insecticides are used in agriculture, medicine, industry and by consumers. Insecticides are claimed to b ...

s 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 cholineste ...

, carbaryl,

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 reaction, substitution, elimination reaction, elimination, and solvation reactions in which water ...

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