Freshwater ostracods (Crustacea: Ostracoda) of the plateaus of the northern Western Ghats, India

Abstract

The role of tropylium ion (Tr+) versus benzylium ion (Bz+) formation by H loss from toluene radical cation (TOL+) was studied by time-resolved photoionization mass spectrometry, by ab initio calculations and by RRKM-QET. Tr+ is not formed at its thermochemical threshold owing to the presence of a reverse activation energy for the reaction leading from the cycloheptatrien radical cation (CHT+) to Tr+ + H. The critical energies required to form Bz+ and Tr+ from TOL+ are very close, being 2.18 and 2.11 eV, respectively. The computational results are in excellent agreement with experiments regarding appearance energies, heats of formation and Tr+/Bz+ abundance ratios as a function of energy. ?? 1993.