Elimination, Fragmentation, and Proton Transfer in 1,3-Dithianes and 1,3-Dithiolanes in the Gas Phase

Article abstract of DOI:10.1021/ja00406a014

The gas-phase negative ion-molecule chemistry of 1,3-dithianes and 1,3-dithiolanes differs considerably from the in solution.When treated with anionic bases, 1,3-dithiane undergoes successive elimination reactions giving thiolates, in competition with deprotonation at the 2-carbon, which is the sole solution phase reaction channel.The appearence of the various product ions with changing base strength agrees with their calculated thermochemical onset.The gase-phase acidity of 1,3-dithiane is measurable if the elimination reaction is blocked by gem-dimethyl substitution at the 5 carbon.For 1,3-dithiolane, no deprotonation product is pbserved; even at thermochemical treshold, cycloreversion to RCS2^- and ethylene occurs.This competes with successive elimination to thiolates, as with the six-membered ring.The differences between the gas phase and solution reactivities are rationalized in terms of counterion effects.