Geo Dijkstra

The use of metastable ion characteristics for the determination of ion structures of some isomeric cannabinoids

The mechanism of formation of the prominent C15H19O2 ion at m/e 231 in the mass spectra of Δ1(6)-tetrahydrocannabinol and five isomeric cannabinoids has been investigated. Except via a well-documented two step process, involving an RDA mechanism, a sizeable percentage of these ions is formed by a novel one-step route from the molecular ion. This was deduced from the spectra of deuterium-labelled compounds and measurements of the kinetic energy release of metastable ions. The latter value for the one step process varies from 25–44 meV for the six compounds investigated, attributed to two interdependent effects, different transition state geometries and common transition states differing in the time elapsing before their formation.

Electron-impact induced fragmentation of some hetero- cyclic-tin compounds

The electron impact induced fragmentation of a series of heterocyclic tin compounds: 10,10-dimethyl- and 10,10-diethylphenoxastannim, the corresponding dimethyl- and diethyltin twelve membered ring heterocycles. 10-10- dimethylphenothiastannin, 10,10-dimethylphenothiastannin 5,5-dioxide, 5,5-dimethyl -5,10-dihydrodibenzo [b,e]stannin and 10,10′ -spirobiphenoxastannin, has been investigated. For the twelve membered ring compounds the results strongly support the structures given by Meinema and Noltes [2]. Primary fragmentation occurs by loss of an alkyl group, in accordance with the preferred tervalency of the tin ion. Further fragmentation pathways were established in each case by defocused metastable measurements and exact mass measurements. Loss of Sn-containing fragments is more common than in Sn- tetraalkyls because of charge stabilisation on the aromatic system. Large differences were observed in molecular ion intensities of the various compounds investigated. Their intensities could be correlated with ionization potentials of the aromatic substituent. A theory attributing this to charge residence in put forward.