Decarbonylation is commonly observed in the 70 eV electron impact mass spectra of a series of S-alkyl thioformates, H-C(=O)SR 1-7. Using a combination of collisional activation (CA) and neutralization-reionization (NR) mass spectra, it is shown that the spectra of the so-formed [M-CO](.+) ions differ from the isomeric alkane thiol ions (RSH.+), if R greater than CH3. These fragment ions are therefore distonic radical cations, and given the fact that the alpha-distonic (CH2)-C-.-S+H2 ions are not present under our experimental conditions, it is proposed that they actually are beta-distonic ions. Strong evidence for the distonic nature of the fragment ions derived from 2-7(.+) has been obtained owing to the use of a new hybrid tandem mass spectrometer presenting a sector-quadrupole-sector configuration. In the case of ethyl derivatives (R = C2H5), both the distonic (CH2CH2S+H2)-C-. (2b) and conventional CH3CH2SH.+ (2a) ions are observed. The nonclassical structure 2b reacts indeed with nitric oxide (NO.) giving the production of H2S+-NO ions (m/z 64), characterized by high-energy collisional activation. Distonic ions 2b have also been otherwise prepared in an ion-molecule reaction involving the transfer of ionized ethene from (CH2CH2O+)-C-.=CH2 to neutral hydrogen sulfide, H2S. Upon CA, the resulting ions 2b show the same behavior as the product of decarbonylation of the S-ethyl thioformate molecular ions. Upon neutralization-reionization, the distonic isomers of the alkane thiol ions give rise to intense peaks corresponding to H2S.+ and ionized olefins. Portions of the potential energy surface related to the rearrangement and dissociation processes in the [C2H6S](.+) system have also been constructed using ab initio molecular orbital calculations Theoretical results provide further support for at the QCISD(T)/6-311++G(d,p)//UMP2/6-31G(d,p) level, the observation of beta-distonic ions.