Amino acid metabolism intermediates
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chemistry Chemistry is the science, scientific study of the properties and behavior of matter. It is a natural science that covers the Chemical element, elements that make up matter to the chemical compound, compounds made of atoms, molecules and ions ...
, amines (, ) are compounds and functional groups that contain a
basic BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming languages designed for ease of use. The original version was created by John G. Kemeny and Thomas E. Kurtz at Dartmouth College ...
nitrogen atom with a
lone pair In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
. Amines are formally
derivatives The derivative of a function is the rate of change of the function's output relative to its input value. Derivative may also refer to: In mathematics and economics * Brzozowski derivative in the theory of formal languages * Formal derivative, an ...
of ammonia (), wherein one or more hydrogen atoms have been replaced by a
substituent A substituent is one or a group of atoms that replaces (one or more) atoms, thereby becoming a moiety in the resultant (new) molecule. (In organic chemistry and biochemistry, the terms ''substituent'' and ''functional group'', as well as ''side ...
such as an alkyl or aryl group (these may respectively be called alkylamines and arylamines; amines in which both types of substituent are attached to one nitrogen atom may be called alkylarylamines). Important amines include amino acids, biogenic amines, trimethylamine, and aniline; Inorganic derivatives of ammonia are also called amines, such as
monochloramine Monochloramine, often called chloramine, is the chemical compound with the formula NH2Cl. Together with dichloramine (NHCl2) and nitrogen trichloride (NCl3), it is one of the three chloramines of ammonia. It is a colorless liquid at its melting p ...
(). The substituent is called an amino group. Compounds with a nitrogen atom attached to a carbonyl group, thus having the structure , are called amides and have different chemical properties from amines.


Classification of amines

Amines can be classified according to the nature and number of substituents on nitrogen. Aliphatic amines contain only H and alkyl substituents. Aromatic amines have the nitrogen atom connected to an aromatic ring. Amines, alkyl and aryl alike, are organized into three subcategories (see table) based on the number of carbon atoms adjacent to the nitrogen(how many hydrogen atoms of the ammonia molecule are replaced by hydrocarbon groups): *Primary (1°) amines—Primary amines arise when one of three hydrogen atoms in ammonia is replaced by an alkyl or aromatic group. Important primary alkyl amines include,
methylamine Methylamine is an organic compound with a formula of . This colorless gas is a derivative of ammonia, but with one hydrogen atom being replaced by a methyl group. It is the simplest primary amine. Methylamine is sold as a solution in methanol, ...
, most amino acids, and the buffering agent tris, while primary aromatic amines include aniline. *Secondary (2°) amines—Secondary amines have two organic substituents (alkyl, aryl or both) bound to the nitrogen together with one hydrogen. Important representatives include dimethylamine, while an example of an aromatic amine would be diphenylamine. *Tertiary (3°) amines—In tertiary amines, nitrogen has three organic substituents. Examples include trimethylamine, which has a distinctively fishy smell, and EDTA. A fourth subcategory is determined by the connectivity of the substituents attached to the nitrogen: *Cyclic amines— Cyclic amines are either secondary or tertiary amines. Examples of cyclic amines include the 3-membered ring
aziridine Aziridine is an organic compound consisting of the three-membered heterocycle . It is a colorless, toxic, volatile liquid that is of significant practical interest. Aziridine was discovered in 1888 by the chemist Siegmund Gabriel. Its derivati ...
and the six-membered ring piperidine. ''N''-methylpiperidine and ''N''-phenylpiperidine are examples of cyclic tertiary amines. It is also possible to have four organic substituents on the nitrogen. These species are not amines but are
quaternary ammonium cation In chemistry, quaternary ammonium cations, also known as quats, are positively charged polyatomic ions of the structure , R being an alkyl group or an aryl group. Unlike the ammonium ion () and the primary, secondary, or tertiary ammonium cations ...
s and have a charged nitrogen center. Quaternary ammonium salts exist with many kinds of anions.


Naming conventions

Amines are named in several ways. Typically, the compound is given the prefix "amino-" or the suffix "-amine". The prefix "''N''-" shows substitution on the nitrogen atom. An organic compound with multiple amino groups is called a diamine, triamine, tetraamine and so forth. Systematic names for some common amines:


Physical properties

Hydrogen bonding significantly influences the properties of primary and secondary amines. For example,
methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
and
ethyl Ethyl may refer to: Arts and entertainment * Cold Ethyl, a Swedish rock band *Ethyl Sinclair, a character in the ''Dinosaurs'' television show Science and technology * Ethyl group, an organic chemistry moiety * Ethyl alcohol (or ethanol) * E ...
amines are gases under standard conditions, whereas the corresponding
methyl In organic chemistry, a methyl group is an alkyl derived from methane, containing one carbon atom bonded to three hydrogen atoms, having chemical formula . In formulas, the group is often abbreviated as Me. This hydrocarbon group occurs in many ...
and
ethyl Ethyl may refer to: Arts and entertainment * Cold Ethyl, a Swedish rock band *Ethyl Sinclair, a character in the ''Dinosaurs'' television show Science and technology * Ethyl group, an organic chemistry moiety * Ethyl alcohol (or ethanol) * E ...
alcohols are liquids. Amines possess a characteristic ammonia smell, liquid amines have a distinctive "fishy" and foul smell. The nitrogen atom features a
lone electron pair In chemistry, a lone pair refers to a pair of valence electrons that are not shared with another atom in a covalent bondIUPAC ''Gold Book'' definition''lone (electron) pair''/ref> and is sometimes called an unshared pair or non-bonding pair. Lone ...
that can bind H+ to form an
ammonium ion 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 ...
R3NH+. The lone electron pair is represented in this article by a two dots above or next to the N. The water solubility of simple amines is enhanced by hydrogen bonding involving these lone electron pairs. Typically salts of ammonium compounds exhibit the following order of solubility in water: primary ammonium () > secondary ammonium () > tertiary ammonium (R3NH+). Small aliphatic amines display significant solubility in many solvents, whereas those with large substituents are lipophilic. Aromatic amines, such as aniline, have their lone pair electrons conjugated into the benzene ring, thus their tendency to engage in hydrogen bonding is diminished. Their boiling points are high and their solubility in water is low.


Spectroscopic identification

Typically the presence of an amine functional group is deduced by a combination of techniques, including mass spectrometry as well as NMR and IR spectroscopies. 1H NMR signals for amines disappear upon treatment of the sample with D2O. In their
infrared spectrum Infrared (IR), sometimes called infrared light, is electromagnetic radiation (EMR) with wavelengths longer than those of visible light. It is therefore invisible to the human eye. IR is generally understood to encompass wavelengths from around ...
primary amines exhibit two N-H bands, whereas secondary amines exhibit only one.


Structure


Alkyl amines

Alkyl amines characteristically feature tetrahedral nitrogen centers. C-N-C and C-N-H angles approach the idealized angle of 109°. C-N distances are slightly shorter than C-C distances. The
energy barrier In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (''E''a) of a reaction is measured in joules per mole (J/mol), kilojoules p ...
for the
nitrogen inversion In chemistry, pyramidal inversion (also umbrella inversion) is a fluxional process in compounds with a pyramidal molecule, such as ammonia (NH3) "turns inside out". It is a rapid oscillation of the atom and substituents, the molecule or ion passin ...
of the stereocenter is about 7  kcal/mol for a trialkylamine. The interconversion has been compared to the inversion of an open umbrella into a strong wind. Amines of the type NHRR' and NRR′R″ are chiral: the nitrogen center bears four substituents counting the lone pair. Because of the low barrier to inversion, amines of the type NHRR' cannot be obtained in optical purity. For chiral tertiary amines, NRR′R″ can only be resolved when the R, R', and R″ groups are constrained in cyclic structures such as N-substituted
aziridine Aziridine is an organic compound consisting of the three-membered heterocycle . It is a colorless, toxic, volatile liquid that is of significant practical interest. Aziridine was discovered in 1888 by the chemist Siegmund Gabriel. Its derivati ...
s ( quaternary ammonium salts are resolvable).


Aromatic amines

In aromatic amines ("anilines"), nitrogen is often nearly planar owing to conjugation of the lone pair with the aryl substituent. The C-N distance is correspondingly shorter. In aniline, the C-N distance is the same as the C-C distances.


Basicity

Like ammonia, amines are bases. Compared to alkali metal hydroxides, amines are weaker (see table for examples of conjugate acid ''K''a values). The basicity of amines depends on: # The electronic properties of the substituents (alkyl groups enhance the basicity, aryl groups diminish it). # The degree of solvation of the protonated amine, which includes steric hindrance by the groups on nitrogen.


Electronic effects

Owing to inductive effects, the basicity of an amine might be expected to increase with the number of alkyl groups on the amine. Correlations are complicated owing to the effects of solvation which are opposite the trends for inductive effects. Solvation effects also dominate the basicity of aromatic amines (anilines). For anilines, the lone pair of electrons on nitrogen delocalizes into the ring, resulting in decreased basicity. Substituents on the aromatic ring, and their positions relative to the amino group, also affect basicity as seen in the table.


Solvation effects

Solvation significantly affects the basicity of amines. N-H groups strongly interact with water, especially in ammonium ions. Consequently, the basicity of ammonia is enhanced by 1011 by solvation. The intrinsic basicity of amines, i.e. the situation where solvation is unimportant, has been evaluated in the gas phase. In the gas phase, amines exhibit the basicities predicted from the electron-releasing effects of the organic substituents. Thus tertiary amines are more basic than secondary amines, which are more basic than primary amines, and finally ammonia is least basic. The order of pKb's (basicities in water) does not follow this order. Similarly aniline is more basic than ammonia in the gas phase, but ten thousand times less so in aqueous solution. In aprotic polar solvents such as DMSO, DMF, and
acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...
the energy of solvation is not as high as in protic polar solvents like water and methanol. For this reason, the basicity of amines in these aprotic solvents is almost solely governed by the electronic effects.


Synthesis


From alcohols

Industrially significant alkyl amines are prepared from ammonia by alkylation with alcohols: :ROH + NH3 -> RNH2 + H2O


From alkyl and aryl halides

Unlike the reaction of amines with alcohols the reaction of amines and ammonia with alkyl halides is used for synthesis in the laboratory: :RX + 2 R'NH2 -> RR'NH + R'NH2 In such reactions, which are more useful for alkyl iodides and bromides, the degree of alkylation is difficult to control such that one obtains mixtures of primary, secondary, and tertiary amines, as well as quaternary ammonium salts. Selectivity can be improved via the Delépine reaction, although this is rarely employed on an industrial scale. Selectivity is also assured in the
Gabriel synthesis The Gabriel synthesis is a chemical reaction that transforms primary alkyl halides into primary amines. Traditionally, the reaction uses potassium phthalimide. The reaction is named after the German chemist Siegmund Gabriel. The Gabriel reaction ...
, which involves organohalide reacting with
potassium phthalimide Potassium phthalimide is a chemical compound of formula C8H4KNO2. It is the potassium salt of phthalimide, and usually presents as fluffy, very pale yellow crystals. It can be prepared by adding a hot solution of phthalimide in ethanol to a soluti ...
. Aryl halides are much less reactive toward amines and for that reason are more controllable. A popular way to prepare aryl amines is the Buchwald-Hartwig reaction.


From alkenes

Disubstituted alkenes react with HCN in the presence of strong acids to give formamides, which can be decarbonylated. This method, the
Ritter reaction The Ritter reaction is a chemical reaction that transforms a nitrile into an ''N''-alkyl amide using various electrophilic alkylating reagents. The original reaction formed the alkylating agent using an alkene in the presence of a strong acid. M ...
, is used industrially to produce tertiary amines such a tert-octylamine. Hydroamination of alkenes is also widely practiced. The reaction is catalyzed by zeolite-based solid acids.


Reductive routes

Via the process of hydrogenation, unsaturated N-containing functional groups are reduced to amines using hydrogen in the presence of a nickel catalyst. Suitable groups include
nitrile In organic chemistry, a nitrile is any organic compound that has a functional group. The prefix ''cyano-'' is used interchangeably with the term ''nitrile'' in industrial literature. Nitriles are found in many useful compounds, including met ...
s,
azide In chemistry, azide is a linear, polyatomic anion with the formula and structure . It is the conjugate base of hydrazoic acid . Organic azides are organic compounds with the formula , containing the azide functional group. The dominant applic ...
s, imines including oximes, amides, and nitro. In the case of nitriles, reactions are sensitive to acidic or alkaline conditions, which can cause hydrolysis of the group. is more commonly employed for the reduction of these same groups on the laboratory scale. Many amines are produced from aldehydes and ketones via reductive amination, which can either proceed catalytically or stoichiometrically. Aniline () and its derivatives are prepared by reduction of the nitroaromatics. In industry, hydrogen is the preferred reductant, whereas, in the laboratory, tin and iron are often employed.


Specialized methods

Many methods exist for the preparation of amines, many of these methods being rather specialized.


Reactions


Alkylation, acylation, and sulfonation, etc.

Aside from their basicity, the dominant reactivity of amines is their
nucleophilicity In chemistry, a nucleophile is a chemical species that forms bonds by donating an electron pair. All molecules and ions with a free pair of electrons or at least one pi bond can act as nucleophiles. Because nucleophiles donate electrons, they are ...
. Most primary amines are good ligands for metal ions to give coordination complexes. Amines are alkylated by alkyl halides.
Acyl chloride In organic chemistry, an acyl chloride (or acid chloride) is an organic compound with the functional group . Their formula is usually written , where R is a side chain. They are reactive derivatives of carboxylic acids (). A specific example o ...
s and acid anhydrides react with primary and secondary amines to form amides (the "
Schotten–Baumann reaction The Schotten–Baumann reaction is a method to synthesize amides from amines and acid chlorides: Schotten–Baumann reaction also refers to the conversion of acid chloride to esters. The reaction was first described in 1883 by German chemists ...
"). Similarly, with sulfonyl chlorides, one obtains
sulfonamide In organic chemistry, the sulfonamide functional group (also spelled sulphonamide) is an organosulfur group with the structure . It consists of a sulfonyl group () connected to an amine group (). Relatively speaking this group is unreactive. ...
s. This transformation, known as the Hinsberg reaction, is a chemical test for the presence of amines. Because amines are basic, they neutralize
acid In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
s to form the corresponding ammonium salts . When formed from carboxylic acids and primary and secondary amines, these salts thermally dehydrate to form the corresponding amides. : \ \underbrace\ce _ \ce Amines undergo sulfamation upon treatment with
sulfur trioxide Sulfur trioxide (alternative spelling sulphur trioxide, also known as ''nisso sulfan'') is the chemical compound with the formula SO3. It has been described as "unquestionably the most important economically" sulfur oxide. It is prepared on an ind ...
or sources thereof: :R2NH + SO3 -> R2NSO3H


Acid-base reactions

Alkyl amines protonate near pH=7 to give alkylammonium derivative.


Diazotization

Amines reacts with nitrous acid to give diazonium salts. The alkyl diazonium salts are of little importance because they are too unstable. The most important members are derivatives of aromatic amines such as aniline ("phenylamine") (A = aryl or naphthyl): :ANH2 + HNO2 + HX -> AN2+ + X- + 2 H2O Anilines and naphthylamines form more stable diazonium salts, which can be isolated in the crystalline form. Diazonium salts undergo a variety of useful transformations involving replacement of the group with anions. For example, cuprous cyanide gives the corresponding nitriles: :AN2+ + Y- -> AY + N2 Aryldiazonium couple with electron-rich aromatic compounds such as a phenol to form azo compounds. Such reactions are widely applied to the production of dyes.


Conversion to Imines

Imine formation In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...
is an important reaction. Primary amines react with
ketone In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s and aldehydes to form imines. In the case of formaldehyde (R'  H), these products typically exist as cyclic trimers. : RNH2 + R'_2C=O -> R'_2C=NR + H2O Reduction of these imines gives secondary amines: :R'_2C=NR + H2 -> R'_2CH-NHR Similarly, secondary amines react with ketones and aldehydes to form enamines: : R2NH + R'(R''CH2)C=O -> R''CH=C(NR2)R' + H2O


Overview

An overview of the reactions of amines is given below:


Biological activity

Amines are ubiquitous in biology. The breakdown of amino acids releases amines, famously in the case of decaying fish which smell of trimethylamine. Many
neurotransmitter A neurotransmitter is a signaling molecule secreted by a neuron to affect another cell across a synapse. The cell receiving the signal, any main body part or target cell, may be another neuron, but could also be a gland or muscle cell. Neuro ...
s are amines, including
epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands and ...
, norepinephrine,
dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...
,
serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...
, and histamine. Protonated amino groups () are the most common positively charged moieties in proteins, specifically in the amino acid
lysine Lysine (symbol Lys or K) is an α-amino acid that is a precursor to many proteins. It contains an α-amino group (which is in the protonated form under biological conditions), an α-carboxylic acid group (which is in the deprotonated −C ...
. The anionic polymer DNA is typically bound to various amine-rich proteins. Additionally, the terminal charged primary ammonium on lysine forms salt bridges with carboxylate groups of other amino acids in
polypeptide Peptides (, ) are short chains of amino acids linked by peptide bonds. Long chains of amino acids are called proteins. Chains of fewer than twenty amino acids are called oligopeptides, and include dipeptides, tripeptides, and tetrapeptides. A p ...
s, which is one of the primary influences on the three-dimensional structures of proteins.


Application of amines


Dyes

Primary aromatic amines are used as a starting material for the manufacture of
azo dye Azo dyes are organic compounds bearing the functional group R−N=N−R′, in which R and R′ are usually aryl and substituted aryl groups. They are a commercially important family of azo compounds, i.e. compounds containing the C-N=N ...
s. It reacts with nitrous acid to form diazonium salt, which can undergo coupling reaction to form an azo compound. As azo-compounds are highly coloured, they are widely used in dyeing industries, such as: * Methyl orange * Direct brown 138 * Sunset yellow FCF * Ponceau


Drugs

Approximately 42% of drugs and drug candidates contain amine functional groups: * Chlorpheniramine is an antihistamine that helps to relieve allergic disorders due to cold, hay fever, itchy skin, insect bites and stings. * Chlorpromazine is a tranquilizer that sedates without inducing sleep. It is used to relieve anxiety, excitement, restlessness or even mental disorder. * Ephedrine and phenylephrine, as amine hydrochlorides, are used as decongestants. *
Amphetamine Amphetamine (contracted from alpha- methylphenethylamine) is a strong central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, and obesity. It is also commonly used ...
,
methamphetamine Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug and less commonly as a second-line treatment for attention deficit hyperactivity disorder and obesity. Methamph ...
, and methcathinone are psychostimulant amines that are listed as controlled substances by the US
DEA The Drug Enforcement Administration (DEA; ) is a United States federal law enforcement agency under the U.S. Department of Justice tasked with combating drug trafficking and distribution within the U.S. It is the lead agency for domestic enf ...
. * Thioridazine , an antipsychotic drug, is an amide which is believed to exhibit its antipsychotic effects, in part, due to its effects on other amides. * Amitriptyline,
imipramine Imipramine, sold under the brand name Tofranil, among others, is a tricyclic antidepressant (TCA) mainly used in the treatment of depression. It is also effective in treating anxiety and panic disorder. The drug is also used to treat bedwetting. ...
, lofepramine and
clomipramine Clomipramine, sold under the brand name Anafranil among others, is a tricyclic antidepressant (TCA). It is used for the treatment of obsessive–compulsive disorder, panic disorder, major depressive disorder, and chronic pain. It may increase th ...
are
tricyclic antidepressant Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and we ...
s and tertiary amines. *
Nortriptyline Nortriptyline, sold under the brand name Pamelor, among others, is a medication used to treat depression. This medicine is used for: neuropathic pain, attention deficit hyperactivity disorder (ADHD), smoking cessation and anxiety. As with many a ...
, desipramine, and amoxapine are
tricyclic antidepressants Tricyclic antidepressants (TCAs) are a class of medications that are used primarily as antidepressants, which is important for the management of depression. They are second-line drugs next to SSRIs. TCAs were discovered in the early 1950s and wer ...
and secondary amines. (The tricyclics are grouped by the nature of the final amino group on the side chain.) *
Substituted tryptamine Substituted tryptamines, or serotonin analogues, are organic compounds which may be thought of as being derived from tryptamine itself. The molecular structures of all tryptamines contain an indole ring, joined to an amino group, amino (NH2) group ...
s and
phenethylamine Phenethylamine (PEA) is an organic compound, natural monoamine alkaloid, and trace amine, which acts as a central nervous system stimulant in humans. In the brain, phenethylamine regulates monoamine neurotransmission by binding to trace amin ...
s are key basic structures for a large variety of
psychedelic drug Psychedelics are a subclass of hallucinogenic drugs whose primary effect is to trigger non-ordinary states of consciousness (known as psychedelic experiences or "trips").Pollan, Michael (2018). ''How to Change Your Mind: What the New Science o ...
s. *
Opiate An opiate, in classical pharmacology, is a substance derived from opium. In more modern usage, the term ''opioid'' is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain (including antagonis ...
analgesic An analgesic drug, also called simply an analgesic (American English), analgaesic (British English), pain reliever, or painkiller, is any member of the group of drugs used to achieve relief from pain (that is, analgesia or pain management). It ...
s such as morphine,
codeine Codeine is an opiate and prodrug of morphine mainly used to treat pain, coughing, and diarrhea. It is also commonly used as a recreational drug. It is found naturally in the sap of the opium poppy, ''Papaver somniferum''. It is typically use ...
, and
heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a potent opioid mainly used as a recreational drug for its euphoric effects. Medical grade diamorphine is used as a pure hydrochloride salt. Various white and brow ...
are tertiary amines.


Gas treatment

Aqueous monoethanolamine (MEA), diglycolamine (DGA), diethanolamine (DEA), diisopropanolamine (DIPA) and methyldiethanolamine (MDEA) are widely used industrially for removing carbon dioxide (CO2) and
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs. The unde ...
(H2S) from natural gas and refinery process streams. They may also be used to remove CO2 from combustion gases and flue gases and may have potential for abatement of
greenhouse gas A greenhouse gas (GHG or GhG) is a gas that Absorption (electromagnetic radiation), absorbs and Emission (electromagnetic radiation), emits radiant energy within the thermal infrared range, causing the greenhouse effect. The primary greenhouse ...
es. Related processes are known as
sweetening Sweetness is a basic taste most commonly perceived when eating foods rich in sugars. Sweet tastes are generally regarded as pleasurable. In addition to sugars like sucrose, many other chemical compounds are sweet, including aldehydes, keton ...
.


Epoxy resin curing agents

Amines are often used as epoxy resin curing agents. These include
dimethylethylamine ''N'',''N''-Dimethylethylamine (DMEA), sometimes referred to as dimethylethylamine, is an organic compound with formula (CH3)2NC2H5. It is an industrial chemical that is mainly used in foundries as a catalyst for epoxy resins and polyurethane as ...
,
cyclohexylamine Cyclohexylamine is an organic compound, belonging to the aliphatic amine class. It is a colorless liquid, although, like many amines, samples are often colored due to contaminants. It has a fishy odor and is miscible with water. Like other amines, ...
, and a variety of diamines such as 4,4 -diaminodicyclohexylmethane. Multifunctional amines such as tetraethylenepentamine and triethylenetetramine are also widely used in this capacity. The reaction proceeds by the lone pair of electrons on the amine nitrogen attacking the outermost carbon on the oxirane ring of the epoxy resin. This relieves ring strain on the epoxide and is the driving force of the reaction.


Safety

Low molecular weight simple amines, such as
ethylamine Ethylamine, also known as ethanamine, is an organic compound with the formula CH3CH2NH2. This colourless gas has a strong ammonia-like odor. It condenses just below room temperature to a liquid miscible with virtually all solvents. It is a nucleo ...
, are only weakly toxic with between 100 and 1000 mg/kg. They are skin irritants, especially as some are easily absorbed through the skin. Amines are a broad class of compounds, and more complex members of the class can be extremely bioactive, for example
strychnine Strychnine (, , US chiefly ) is a highly toxic, colorless, bitter, crystalline alkaloid used as a pesticide, particularly for killing small vertebrates such as birds and rodents. Strychnine, when inhaled, swallowed, or absorbed through the eye ...
and
heroin Heroin, also known as diacetylmorphine and diamorphine among other names, is a potent opioid mainly used as a recreational drug for its euphoric effects. Medical grade diamorphine is used as a pure hydrochloride salt. Various white and brow ...
.


See also

* Acid-base extraction *
Amine value 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 substituent such a ...
* Amine gas treating * Ammine * Biogenic amine *
Ligand isomerism In coordination chemistry, ligand isomerism is a type of structural isomerism in coordination complexes which arises from the presence of ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a c ...
* Official naming rules for amines as determined by the International Union of Pure and Applied Chemistry ( IUPAC)


References


Further reading

* *


External links


Synthesis of amines

Factsheet, amines in food
{{Authority control Functional groups