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High temperature collisional energy transfer in highly vibrationally excited molecules. III: Isotope effects in tert ‐butyl bromide systems
Author(s) -
Brown Trevor C.,
King Keith D.,
Gilbert Robert G.
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.550200705
Subject(s) - chemistry , excited state , kinetic isotope effect , bromide , isotope , analytical chemistry (journal) , molecule , kinetic energy , thermal decomposition , inert gas , vinyl bromide , atomic physics , deuterium , inorganic chemistry , medicinal chemistry , organic chemistry , physics , quantum mechanics
Abstract Changes in the magnitude of 〈Δ E down 〉, the average downward collisional energy transferred between a highly vibrationally excited reactant molecule and an inert bath gas, upon perdeuteration of the substrate are reported for tert ‐butyl bromide dilute in Ar, Kr, N 2 , and CO 2 . The technique of pressure‐dependent very low‐pressure pyrolysis (VLPP) was used to obtain the absolute values of 〈Δ E down 〉, which are for C 4 H 9 Br, 230 (Ar), 285 (Kr), 270 (N 2 ), and 365 (CO 2 ) while for C 4 D 9 Br, 200 (Ar), 250 (Kr), 220 (N 2 ), and 335 (CO 2 ), all in cm −1 at ca. 720 K. The estimated uncertainties in these values are ca. ± 10%. These observed 〈Δ E down 〉, values and trends found with results from this series of isotope studies, are compared with current theoretical models. Extrapolated high‐pressure temperature‐dependent rate coefficients (s −1 ) for the thermal decomposition of reactant are 10 13.8±0.3 exp(−175 ± 8 kJ mol −1 /RT) for C 4 H 9 Br and 10 14.3±0.3 exp(−183 ± 8 kJ mol −1 /RT) for C 4 D 9 Br. These results are in accord with other studies and the expected isotope effect.