The gas phase reactivity of the methoxymethyl cation, an ambident electrophile, towards 21 neutral nucleophiles has been probed using the flowing afterglow technique. The classes of compounds studied includes alcohol, ethers, thiols, thioethers, aliphatic ketones, acids, esters and amides as well as the following aromatics: benzene, pyridine and aniline. Three general types of reaction channels were observed: addition followed by elimination of methanol with concomitant [M + CH] + ion formation S N 2 methylation resulting in [M + CH 3 ] + ion formation and adduct ([M + CH 3 OCH 2 ] + ) formation. Formamide and N,N-dimethylformamide both yield additional products arising from cleavage of the amide bond by CH 3 OCH + 2 . In addition, ab initio techniques (at the MP2(fc)/6-31G * level) have been used to investigate the [M + CH] + and [M + CH 3 ] + ion formation channels for the reactions of CH 3 OCH + 2 with NH 3 , H 2 O and H 2 S. These ab initio results suggest that the reactivity order should be: NH 3 > H 2 S > H 2 O, in line with the experimental observations.