An intermolecular methyl transfer during field desorption mass spectrometry. Identification of the [M + 14] peak in choline chloride

Choline chloride, bromide and iodide all contain a peak at m / e 118 [M + 14] in their field desorption mass spectra. Comparison with choline(methyl‐d 9 ) chloride demonstrates that this peak arises from an intermolecular transfer of a methyl group. Partial exchange of hydroxyl hydrogen on choline chloride does not displace the m / e 118 peak, suggesting that this hydrogen is lost during methyl transfer. The structure of the [M + 14] species should then correspond to choline methyl ether.