Dimethylaniline
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''N'',''N''-Dimethylaniline (DMA) is an
organic chemical compound Some chemical authorities define an organic compound as a chemical compound that contains a Carbon–hydrogen bond, carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. F ...
, a substituted derivative of
aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...
. It is a
tertiary amine In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
, featuring a dimethylamino group attached to a
phenyl In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula , and is often represented by the symbol Ph (archaically φ) or Ø. The phenyl group is closely related to benzene and can be viewed as a benzene ...
group. This oily liquid is colourless when pure, but commercial samples are often yellow. It is an important precursor to dyes such as
crystal violet Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triphenylmethane, triarylmethane dye used as a histological stain and in Gram staining, Gram's method of classifying bacteria. Crystal ...
.


Preparation

DMA was first reported in 1850 by the German chemist A. W. Hofmann, who prepared it by heating aniline and
iodomethane Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one hy ...
: :C6H5NH2 + 2 CH3I → C6H5N(CH3)2 + 2 HI DMA is produced industrially by
alkylation Alkylation is a chemical reaction that entails transfer of an alkyl group. The alkyl group may be transferred as an alkyl carbocation, a free radical, a carbanion, or a carbene (or their equivalents). Alkylating agents are reagents for effecting al ...
of
aniline Aniline (From , meaning ' indigo shrub', and ''-ine'' indicating a derived substance) is an organic compound with the formula . Consisting of a phenyl group () attached to an amino group (), aniline is the simplest aromatic amine. It is an in ...
with
methanol Methanol (also called methyl alcohol and wood spirit, amongst other names) is an organic chemical compound and the simplest aliphatic Alcohol (chemistry), alcohol, with the chemical formula (a methyl group linked to a hydroxyl group, often ab ...
in the presence of an acid catalyst:Kahl, Thomas ''et al.'' (2007) "Aniline" in ''Ullmann's Encyclopedia of Industrial Chemistry''. John Wiley & Sons: New York. :C6H5NH2 + 2 CH3OH → C6H5N(CH3)2 + 2 H2O Similarly, it is also prepared using
dimethyl ether Dimethyl ether (DME; also known as methoxymethane) is the organic compound with the formula CH3OCH3, (sometimes ambiguously simplified to C2H6O as it is an isomer of ethanol). The simplest ether, it is a colorless gas that is a useful precursor ...
as the methylating agent.


Reactions

Dimethylaniline undergoes many of the reactions expected for an aniline, being weakly basic and reactive toward electrophiles. It is nitrated to produce
tetryl 2,4,6-Trinitrophenylmethylnitramine or tetryl ( C7 H5 N5 O8) is an explosive compound used to make detonators and explosive booster charges. Tetryl is a nitramine booster explosive, though its use has been largely superseded by RDX. Tetryl is a ...
, a derivative with four
nitro Nitro may refer to: Chemistry *Nitrogen, a chemical element and a gas except at very low temperatures, with which many compounds are formed: **Nitro compound, an organic compound containing one or more nitro functional groups, -NO2 **Nitro ligand ...
groups which was once used as explosive. In acidic solution, the initial nitration gives 3-nitrodimethylaniline. It reacts with
butyllithium Butyllithium may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis: * ''n''-Butyllithium, abbreviated BuLi or nBuLi * ''sec''-Butyllithium, abbreviated ''sec''-BuLi or sBuLi, has 2 stereoisomers, ...
to give the 2-lithio derivative. Electrophilic methylating agents like
dimethyl sulfate Dimethyl sulfate (DMS) is a chemical compound with formula (CH3O)2SO2. As the diester of methanol and sulfuric acid, its formula is often written as ( CH3)2 SO4 or Me2SO4, where CH3 or Me is methyl. Me2SO4 is mainly used as a methylating agen ...
attack the amine to give the quaternary ammonium salt: :C6H5N(CH3)2 +(CH3O)2SO2 → C6H5N(CH3)3CH3OSO3 Diethylaniline and dimethylaniline are both used as acid-absorbing bases.


Applications

DMA is a key precursor to commercially important
triarylmethane dye Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes. Families Triarylmethane dyes can be grouped into families accordin ...
s such as
malachite green Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is ...
and
crystal violet Crystal violet or gentian violet, also known as methyl violet 10B or hexamethyl pararosaniline chloride, is a triphenylmethane, triarylmethane dye used as a histological stain and in Gram staining, Gram's method of classifying bacteria. Crystal ...
. DMA serves as a promoter in the curing of polyester and vinyl ester resins. DMA is also used as a precursor to other organic compounds. A study of the in vitro metabolism of ''N,N''-dimethylaniline using guinea pig and rabbit preparations and GLC techniques has confirmed ''N''-demethylation and ''N''-oxidation as metabolic pathways, and has also established ring hydroxylation as a metabolic route.


References

{{reflist Anilines Dimethylamino compounds tertiary amines