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The high temperature pyrolysis of 1,3‐butadiene II: Pulsed laser flash absorption rate constants, and consideration of possible molecular dissociation pathways
Author(s) -
Kiefer J. H.,
Mitchell K. I.,
Wei H. C.
Publication year - 1988
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.550201004
Subject(s) - chemistry , dissociation (chemistry) , reaction rate constant , flash photolysis , mass spectrometry , radical , analytical chemistry (journal) , photochemistry , laser , kinetics , organic chemistry , physics , chromatography , quantum mechanics , optics
Rate constants for the unimolecular dissociation of 1,3‐butadiene have been measured with the pulsed laser flash absorption technique, following butadiene disappearance at 222 nm. The results are in excellent agreement with previous laser‐schlieren measurements interpreted with a ΔH° 298 = 100 kcal/mol heat of dissociation. A new RRKM calculation agreeing with both sets of rate constants gives log k ∞ (s −1 ) = 17.03 ± 0.3 – 94(kcal/mol)/ RT . These data and product measurements using ARAS, single‐pulse product analysis, and time‐of‐flight mass spectrometry, in shock tubes, all provide independent evidence against any major participation by molecular reactions in the dissociation. The only dissociation channel, or combination of channels, consistent with all the measurements is C‐C scission to two vinyl radicals. However, the extremely slow rate of H‐atom formation seen in ARAS experiments then requires an unacceptably low rate of vinyl dissociation.