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The unimolecular dissociation of 3,4‐dihydro‐2H‐pyran over a wide temperature range
Author(s) -
Besseris G. J.,
Kiefer J. H.,
Zhang Q.,
Walker J. A.,
Tsang W.
Publication year - 1995
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/kin.550270708
Subject(s) - chemistry , arrhenius equation , dissociation (chemistry) , shock tube , atmospheric temperature range , reaction rate constant , thermodynamics , thermal decomposition , krypton , torr , difluoromethane , ethylene , shock wave , analytical chemistry (journal) , argon , kinetics , activation energy , organic chemistry , refrigerant , physics , quantum mechanics , gas compressor , catalysis
The thermal decomposition of 3,4‐dihydro‐2H‐pyran (DHP, C 5 H 8 O) has been investigated by two methods: in shock waves with the laser‐schlieren technique using mixtures of 5 and 10% DHP in krypton over 900–1500 K, 110–560 torr; in a flow tube having a reaction pressure 0.5 torr above atmospheric using the decomposition of allylethyl ether as an internal standard, and covering 663–773 K. The retro‐Diels‐Alder dissociation to the stable acrolein and ethylene is the dominant channel for all conditions. Precise rate constants (rms deviation of 10%) were obtained for this process over the indicated temperature ranges. Unimolecular falloff is evident in the shock‐tube results, and RRKM calculations also predict a slight falloff at the lower temperatures. These RRKM calculations use a routine vibration model transition state and agree closely with the high‐temperature data when 〈Δ E 〉 down is a fixed 400 cm −1 . Arrhenius expressions for k ∞ derived from the two measurements are in close accord and also consistent with most previous studies of this reaction. © 1995 John Wiley & Sons, Inc.