ELECTRON-IMPACT STUDIES .125. NEGATIVE-ION MASS-SPECTRA OF THIOBENZAMIDES - DUAL MECHANISMS FOR LOSS OF NO FROM ORTHO-NITROTHIOBENZAMIDES

Molecular anions of thiobenzamides ArC(S)N(R1R2) (R = alkyl) fragment by the cleavages M-∓ → (M - R1 ∓)- and M-∓ → (M - R2 ∓)-, with loss of the larger alkyl predominating. o-Nitrothiobenzamides o-NO2C6H4C(S)N(R1R2 ) eliminate R1R2N∓ from their molecular anions following cyclisation between the two functional groups. The observation of composite metastable peaks for loss of NO∓ from the molecular anions of the o-compounds shows that two mechanisms are operating. It is proposed that the process having the larger T value corresponds to the normal loss of NO∓ from -NO2 -∓, whereas that having the smaller value arises from loss of NO∓ from an -NOS-∓ group formed by rearrangement. © 1979.