1-Methylimidazole

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. 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.{{cite journal | trans-title = By the Constitution of the Lophins and related compounds

:(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. Similarly, 1-methylimidazole may be synthesized by first deprotonating imidazole to form a sodium salt followed by methylation. :H2C2N(NH)CH + CH3I → [H2C2(NH)(NCH3)CH]I :[H2C2(NH)(NCH3)CH]I + 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.

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"):

:[[File:MeIm IL.png|500px]]

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 hydrochloride, which spontaneously separates as a separate liquid phase under the reaction conditions.

:2 MeC3N2H3 + C6H5PCl2 + 2 C2H5OH → 2 [MeC3N2H4]Cl + C6H5P(OC2H5)2

Donor properties

1-methylimidazole (NMIz) as a ligand forms octahedral ions M(NMIz)62+with M = Fe, Co, Ni, and a square-planar ion Cu(NMIz)42+. 1-methylimidazole forms adducts with Lewis acids such as molybdenum perfluorobutyrate and [Rh(CO)2Cl]2. The donor properties of 1-methylimidazole have been analyzed by the ECW model yielding EB= 1.16 and CB= 4.92.

References

References

1. Albert, A., Heterocyclic Chemistry, 2nd ed.; 1968 Athlone Press, {{ISBN. 0-485-11092-X
2. Ebel, K.. (2002). "Imidazole and Derivatives".
3. Gilchrist, T. L., Heterocyclic Chemistry, 2nd ed.; 1992 Longman Scientific & Technical, {{ISBN. 0-582-06420-1
4. Grimmett, M. R., Imidazole and Benzimidazole Synthesis; 1997 Academic Press, {{ISBN. 0-12-303190-7
5. Gupta, R. R., Kumar, M., Gupta, V., Heterocyclic Chemistry II: Five Membered Heterocycles; 1999 Springer, {{ISBN. 3-540-65252-3
6. (1996). "Solid Phase Synthesis of Polyamides Containing Imidazole and Pyrrole Amino Acids". Journal of the American Chemical Society.
7. (2007). "Ullmann's Encyclopedia of Industrial Chemistry". Wiley-VCH.
8. Dupont, J.. (2002). "Preparation of 1-Butyl-3-methyl imidazolium-based Room Temperature Ionic Liquids".
9. (11 November 2015). "Solvents and sustainable chemistry". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences.
10. (1969). "Pyrazoles and imidazoles as ligands. II. Coordination compounds of N-methyl imidazole with metal perchlorates and tetrafluoroborates". Inorganica Chimica Acta.