In organic chemistry, a methiodide is a chemical derivative produced by the reaction of a compound with
methyl iodide
Iodomethane, also called methyl iodide, and commonly abbreviated "MeI", is the chemical compound with the formula CH3I. It is a dense, colorless, volatile liquid. In terms of chemical structure, it is related to methane by replacement of one h ...
. Methiodides are often formed through the
methylation
Methylation, in the chemistry, chemical sciences, is the addition of a methyl group on a substrate (chemistry), substrate, or the substitution of an atom (or group) by a methyl group. Methylation is a form of alkylation, with a methyl group replac ...
of
tertiary amine
In chemistry, amines (, ) are organic compounds that contain carbon-nitrogen bonds. Amines are formed when one or more hydrogen atoms in ammonia are replaced by alkyl or aryl groups. The nitrogen atom in an amine possesses a lone pair of elec ...
s:
: R
3N + CH
3I → (CH
3)R
3N
+I
−
Whereas the parent amines are hydrophobic and often oily, methiodides, being salts, are somewhat hydrophilic and exhibit high
melting point
The melting point (or, rarely, liquefaction point) of a substance is the temperature at which it changes state of matter, state from solid to liquid. At the melting point the solid and liquid phase (matter), phase exist in Thermodynamic equilib ...
s. Methiodides exhibit altered pharmacological properties as well.
Examples include:
* Cocaine methiodide, a charged
cocaine
Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...
analog which cannot pass the
blood brain barrier and enter the brain
* Bicuculline methiodide, a water-soluble form of
bicuculline
Tertiary phosphines and
phosphite esters also form methiodides.
References
Quaternary ammonium compounds
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