Thermal decomposition of 3,6-dihydro-2H-pyran

Abstract

The thermal decomposition of the title compound has been studied in the gas phase in the temperature range 329–374 °C. The reaction yields formaldehyde and buta-1,3-diene quantitatively by a process that is homogeneous, kinetically strictly first order, and probably unimolecular. The measured rate constants yield the Arrhenius equation: log k/s^–1= 14.31 ± 0.14 –(208.1 ± 1.7)kJ mol^–1/RTIn10 The results of the present study are compared with those for some 3,4-dihydro-2H-pyrans and also cis-2,6-di-methyl-3,6-dihydro-2H-pyran. It is concluded that the decomposition is concerted and that the activated complexes, which are similar for these molecules, have some polar character.