methiodide

In organic chemistry, a methiodide is a chemical derivative produced by the reaction of a compound with methyl iodide. Methiodides are often formed through the methylation of tertiary amines:

: R₃N + CH₃I → (CH₃)R₃N⁺I⁻

Whereas the parent amines are hydrophobic and often oily, methiodides, being salts, are somewhat hydrophilic and exhibit high melting points. Methiodides exhibit altered pharmacological properties as well.

Examples include:

• Cocaine methiodide, a charged cocaine analog which cannot pass the blood brain barrier and enter the brain{{cite journal | title = Potencies of Cocaine Methiodide on Major Cocaine Targets in Mice | vauthors = Hill ER, Tian J, Tilley MR, Zhu MX, Gu HH | journal = PLOS ONE | year = 2009 | volume = 4 | pmid = 19855831 | issue = 10 | pmc = 2762027 | pages = e7578 | doi = 10.1371/journal.pone.0007578 | editor1-last = Manzoni | editor1-first = Olivier Jacques|bibcode = 2009PLoSO...4.7578H | doi-access = free }}
• Bicuculline methiodide, a water-soluble form of bicuculline

Tertiary phosphines and phosphite esters also form methiodides.{{cite journal |author=H. N. Rydon|doi=10.15227/orgsyn.051.0044|title=Alkyl Iodides: Neopentyl Iodide and Iodocyclohexane|journal=Organic Syntheses|year=1971|volume=51|page=44}}