Dimethylaniline

Preparation

DMA was first reported in 1850 by the German chemist A. W. Hofmann, who prepared it by heating aniline and iodomethane:In 1850, August Hofmann announced his synthesis of methylaniline:

• Hofmann, A. W. (1850) "Researches regarding the molecular constitution of the volatile organic bases," Philosophical Transactions of the Royal Society of London, 140 : 93–131 ; see especially pp. 113-114. However, in 1877, the Swiss chemist Alfred Kern (1850–1893) contended that Hofmann's reaction produced only dimethylaniline, not methylaniline:
• Kern, A. (1877) "Ueber die Darstellung von Monomethylanilin" (On the preparation of monomethylaniline), Berichte der deutschen chemischen Gesellschaft, 10 : 195–199. Hofmann found that acetic anhydride reacted only with methylaniline, not with dimethylaniline, and was thus able to show that his reaction produced both the mono- and di-methylated forms of aniline:
• Hofmann, A. W. (1877) "Versuche über die Einwirkung des Chlor-, Brom- und Jodmethyls auf Anilin" (Experiments on the reaction of methyl chloride, bromide and iodide with aniline), Berichte der deutschen chemischen Gesellschaft, 10 : 591–601. :C6H5NH2 + 2 CH3I → C6H5N(CH3)2 + 2 HI DMA is produced industrially by alkylation of aniline with methanol in the presence of an acid catalyst: :C6H5NH2 + 2 CH3OH → C6H5N(CH3)2 + 2 H2O Similarly, it is also prepared using dimethyl ether 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, a derivative with four nitro groups which was once used as explosive. In acidic solution, the initial nitration gives 3-nitrodimethylaniline. It reacts with butyllithium to give the 2-lithio derivative. Electrophilic methylating agents like dimethyl sulfate 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 dyes such as malachite green and crystal violet. 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

References

1. {{PGCH. 0223
2. {{IDLH. 121697. N,N-Dimethylaniline
3. Watts, Henry, ''A Dictionary of Chemistry and the Allied Branches of Other Sciences'', Part 2, (London, England: Longmans, Green, and Co., 1881), Methylanilines, [https://books.google.com/books?id=NfMfAQAAMAAJ&pg=PA1306 p. 1306]
4. Kahl, Thomas ''et al.'' (2007) "Aniline" in ''Ullmann's Encyclopedia of Industrial Chemistry''. John Wiley & Sons: New York. {{doi. 10.1002/14356007.a02_303
5. (1939). "P-Thiocyanatodimethylaniline". Organic Syntheses.
6. Howard M. Fitch. (1947). "m-Nitrodimethylaniline". Organic Syntheses.
7. Jacques, J. and Marquet, A.. (1973). "Selective α-Bromination of an Aralkyl Ketone with Phenyltrimethylammonium Tribromide: 2-Bromoacetyl-6-methoxynaphthalene and 2,2-Dibromoacetyl-6-Methoxynaphthalene".
8. Gessner, Thomas and Mayer, Udo (2002) "Triarylmethane and Diarylmethane Dyes" in ''Ullmann's Encyclopedia of Industrial Chemistry''. Wiley-VCH, Weinheim.{{doi. 10.1002/14356007.a27_179
9. [https://www.compositesaustralia.com.au/for-industry/health-and-safety/dma/ General Info on DMA (N,N-Dimethylaniline)], Composites Australia
10. (1981). "The in vitro metabolism of N,N-dimethylaniline by guinea pig and rabbit tissue preparations". European Journal of Drug Metabolism and Pharmacokinetics.