1-Methylimidazole

1-Methylimidazole
IUPAC name 1-Methylimidazole
Other names N-Methylimidazole
Identifiers
CAS number	616-47-7 Y
ChemSpider	1348 Y
ChEBI	CHEBI:113454 Y
ChEMBL	CHEMBL543 Y
Jmol-3D images	Image 1 Image 2
SMILES n1ccn(c1)C Cn1ccnc1
InChI InChI=1S/C4H6N2/c1-6-3-2-5-4-6/h2-4H,1H3 Y Key: MCTWTZJPVLRJOU-UHFFFAOYSA-N Y InChI=1/C4H6N2/c1-6-3-2-5-4-6/h2-4H,1H3 Key: MCTWTZJPVLRJOU-UHFFFAOYAU
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)
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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]

H₂C_{2N(NH)CH + CH3I → [H2C2(NH)(NCH3)CH]I}

H₂C_{2(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

See also

• 4-Methylimidazole

References