Mass spectrometry of aralkyl compounds with a functional group—XII: Unorthodox elimination of hydrogen cyanide from hydrogen randomized molecular ions of benzylcyanide and of o-, m- and p-cyanobenzylcyanides,revealed by D-, 13C- acid 15N-labelling

Specific D-labelling in the side-chain and in the phenyl ring, ¹³C-labelling in the benzylic position and in the cyano group and ¹⁵N-labelling in the cyano group of benzylcyanide show, that the molecular ion, decomposing in the second field free region, i.e. having a low internal energy, loses hydrogen cyanide with participation of both side-chain carbon atoms (22% benzylic carbon and 78% cyano carbon) after a complete randomization of all hydrogens. This sharply contrasts with the loss of hydrogen cyanide from the hydrogen randomized molecular ion, decomposing in the ion source, where the original cyano group is involved exclusively. The molecular ions of (o, m, p)-cyanobenzylcyanides, decomposing in the ion source as well as in the second field free region, also lose hydrogen cyanide, involving to some extent (6 to 15%) a carbon atom, different from that of the side-chain cyano group, after an extensive randomization of hydrogens as shown by specific D-labelling in several positions and by ¹³C- and ¹⁵N-labelling in the side-chain cyano group. Furthermore, the molecule of hydrogen cyanide, eliminated in the ion source and in the second field free region, appears to contain predominantly the side-chain cyano group (±70%), thus suggesting that few or none of the molecular ions have rearranged to a seven membered ring.