1-Methylimidazole
| 1-Methylimidazole | |
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1-Methylimidazole |
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Other names
N-Methylimidazole |
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| Identifiers | |
| CAS number | 616-47-7  |
| ChemSpider | 1348 |
| ChEBI | CHEBI:113454 |
| ChEMBL | CHEMBL543 |
| Jmol-3D images | Image 1 Image 2 |
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| Properties | |
| Molecular formula | C4H6N2 |
| Molar mass | 82.10 g/mol |
| Density | 1.03 g/cm³ |
| Melting point |
-6°C |
| Boiling point |
198 °C |
| Hazards | |
| MSDS | Oxford MSDS |
| EU classification | Harmful (Xn); Corrosive (C) |
 (verify) (what is:  / ?)Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
1-Methylimidazole or N-Methylimidazole is an aromatic heterocyclic organic compound with the formula CH3C3H3N2. It is a colourless liquid that is used as a specialty solvent, a base, and as a precursor to some ionic liquids. It is fundamental nitrogen heterocycle and as such mimics for various nucleoside bases as well as histidine and histamine,
Basicity
With the N-methyl group, this particular derivative of imidazole cannot tautomerize. It is slightly more basic than imidazole, as indicated by the pKa's of the conjugate acids of 7.0 and 7.4.[1] Methylation also provides a significantly lower melting point, which makes 1-methylimidazole a useful solvent.
Synthesis
1-Methylimidazole is prepared mainly by two routes industrially. The main one is acid-catalysed methylation of imidazole by methanol. The second method involves the Radziszewski reaction from glyoxal, formaldehyde, and a mixture of ammonia and methylamine.[2][3]
- (CHO)2 + CH2O + CH3NH2 + NH3 → H2C2N(NCH3)CH + 3 H2O
The compound can be synthesized on a laboratory scale by methylation of imidazole at the pyridine-like nitrogen and subsequent deprotonation.[4] Similarly, 1-methylimidazole may be synthesized by first deprotonating imidazole to form a sodium salt followed by methylation.[5][6]
- H2C2N(NH)CH + CH3I → [H2C2(NH)(NCH3)CH]I
- H2C2(NH)(NCH3)CH + NaOH → H2C2N(NCH3)CH + H2O + NaI
Applications
In the research laboratory, 1-methylimidazole and related derivatives have been used as mimic aspects of diverse imidazole-based biomolecules.
1-Methylimidazole is also the precursor for the synthesis of the methylimidazole monomer of pyrrole-imidazole polyamides. These polymers can selectively bind specific sequences of double-stranded DNA by intercalating in a sequence dependent manner.[7]
Ionic liquid precursor
1-Methylimidazole alkylates to form dialkyl imidazolium salts. Depending on the alkylating agent and the counteranion, various ionic liquids result, e.g. 1-butyl-3-methylimidazolium hexafluorophosphate ("BMIMPF6"):[8][9]
BASF has used 1-methylimidazole as a means to remove acid during their industrial-scale production of diethoxyphenylphosphine. In this biphasic acid scavenging using ionic liquids (BASIL) process, 1-methylimidazole reacts with HCl to produce 1-methylimidazolium chloride, a salt that is easily separated and deprotonated to regenerate 1-methylimidazole.[8]
- 2 MeC3N2H3 + C6H5PCl2 + 2 C2H5OH → 2 [MeC3N2H4]Cl + C6H5P(OC2H5)2
References
- ^ Albert, A., Heterocyclic Chemistry, 2nd ed.; 1968 Athlone Press, ISBN 0-485-11092-X
- ^ Ebel, K., Koehler, H., Gamer, A. O., & Jäckh, R. “Imidazole and Derivatives.” In Ullmann’s Encyclopedia of Industrial Chemistry; 2002 Wiley-VCH, doi:10.1002/14356007.a13_661
- ^ Bronislas Radziszewski (1882). "Ueber die Constitution des Lophins und verwandter Verbindungen". Berichte der deutschen chemischen Gesellschaft 15 (2): 1493–1496. doi:10.1002/cber.18820150207.
- ^ Gilchrist, T. L., Heterocyclic Chemistry, 2nd ed.; 1992 Longman Scientific & Technical, ISBN 0-582-06420-1
- ^ Grimmett, M. R., Imidazole and Benzimidazole Synthesis; 1997 Academic Press, ISBN 0-12-303190-7
- ^ Gupta, R. R., Kumar, M., Gupta, V., Heterocyclic Chemistry II: Five Membered Heterocycles; 1999 Springer, ISBN 3-540-65252-3
- ^ Baird, E.E. & Dervan, P.B. J. Am. Chem. Soc. 118 (26), 6141-6146, 1996.
- ^ a b Meindersma, W., Maase, M., and De Haan, A. B. “Ionic Liquids.” In Ullmann’s Encyclopedia of Industrial Chemistry; 2007 Wiley-VCH, doi:10.1002/14356007.l14_l01
- ^ Dupont, J., Consorti, C., Suarez, P., de Souza, R. (2004), "Preparation of 1-Butyl-3-methyl imidazolium-based Room Temperature Ionic Liquids", Org. Synth.; Coll. Vol. 10: 184
