The thermal unimolecular decomposition of 2-methoxy-3,4-dihydro-2H-pyran

Abstract

The thermal decomposition of 2-methoxy-3,4-dihydro-2H-pyran has been studied in the gas phase from 296 to 353 °C. Methyl vinyl ether and acraldehyde are formed quantitatively by a process which is homogeneous, of the first order, and almost certainly unimolecular. The rate constants fit the Arrhenius equation (i). Comparison of the, log k/s^–1= 14·42 ± 0·04 – 203,100 ± 450 J mol^–1/2·303RT(i) results obtained here with those for the thermal decomposition of 3,4-dihydro-2H-pyran and 6-methyl-3,4-dihydro-2H-pyran suggest that all these reactions are concerted.