1-Methylimidazole or ''N''-methylimidazole is an
aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
heterocyclic
A heterocyclic compound or ring structure is a cyclic compound that has atoms of at least two different elements as members of its ring(s). Heterocyclic chemistry is the branch of organic chemistry dealing with the synthesis, properties, and ...
organic compound with the formula CH
3C
3H
3N
2. It is a colourless liquid that is used as a specialty solvent, a base, and as a precursor to some ionic liquids. It is a 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
Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-a ...
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
Imidazole (ImH) is an organic compound with the formula C3N2H4. It is a white or colourless solid that is soluble in water, producing a mildly alkaline solution. In chemistry, it is an aromatic heterocycle, classified as a diazole, and has non-a ...
by
methanol. The second method involves the
Radziszewski reaction from
glyoxal
Glyoxal is an organic compound with the chemical formula OCHCHO. It is the smallest dialdehyde (a compound with two aldehyde groups). It is a crystalline solid, white at low temperatures and yellow near the melting point (15 °C). The liquid ...
,
formaldehyde
Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section ...
, and a mixture of
ammonia
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
and
methylamine.
:(CHO)
2 + CH
2O + CH
3NH
2 + NH
3 → H
2C
2N(NCH
3)CH + 3 H
2O
The compound can be synthesized on a laboratory scale by
methylation of imidazole at the
pyridine
Pyridine is a basic heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom. It is a highly flammable, weakly alkaline, water-miscible liquid with a ...
-like nitrogen and subsequent deprotonation. Similarly, 1-methylimidazole may be synthesized by first deprotonating imidazole to form a sodium salt followed by methylation.
:H
2C
2N(NH)CH + CH
3I →
2C2(NH)(NCH3)CH">2C2(NH)(NCH3)CH
:
2C2(NH)(NCH3)CH">2C2(NH)(NCH3)CH + NaOH → H
2C
2N(NCH
3)CH + H
2O + 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
Alkylation is the transfer of an alkyl group from one molecule to another. 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 effectin ...
and the counteranion, various
ionic liquid
An ionic liquid (IL) is a salt in the liquid state. In some contexts, the term has been restricted to salts whose melting point is below a specific temperature, such as . While ordinary liquids such as water and gasoline are predominantly made of ...
s result, e.g.
1-butyl-3-methylimidazolium hexafluorophosphate ("BMIMPF
6"):
:
![MeIm IL](https://upload.wikimedia.org/wikipedia/commons/f/f7/MeIm_IL.png)
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 3N2H4">eC3N2H4l + C6H5P(OC2H5)2
Like other imidazoles, 2-methylimidazole undergoes alkylation to give PREPARATION OF 1-BUTYL-3-METHYL IMIDAZOLIUM-BASED ROOM TEMPERATURE IONIC LIQUIDS
]
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 2Clsub>2">h(CO)2Clsub>2. The donor properties of 1-methylimidazole have been analyzed by the ECW model yielding EB= 1.16 and CB= 4.92.
See also
* 4-Methylimidazole
References
{{DEFAULTSORT:Methylimidazole, 1-
Imidazoles
Solvents