diazomethane

 
Pronunciation: /dʌɪˌazəʊˈmiːθeɪn, -ˌeɪzəʊ-/

noun

[mass noun] Chemistry
  • a poisonous, reactive yellow gas used as a methylating agent in chemical synthesis.
    • Chemical formula: CH2N2

Origin:

late 19th century: from diazo- (indicating the presence of two nitrogen atoms) + methane