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Self‐inhibition or the lack of it in the pyrolyses of neopentane and n ‐hexane
Author(s) -
Marshall Roger M.
Publication year - 1987
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.550190707
Subject(s) - neopentane , chemistry , olefin fiber , hexane , allylic rearrangement , pyrolysis , photochemistry , decomposition , reactivity (psychology) , disproportionation , hydrogenolysis , hydrogen atom abstraction , organic chemistry , medicinal chemistry , hydrogen , catalysis , molecule , medicine , alternative medicine , pathology
Published data show that in its early stages (up to 3% decomposition), the pyrolysis of n ‐hexane in the ranges 723–823 K and 10–100 Torr is not inhibited by the olefin products, in contrast with neopentane pyrolysis which is very strongly inhibited in similar conditions. Detailed consideration of the chain mechanisms for the two pyrolyses shows that the reactivity of the chain terminating radical towards hydrogen abstraction from an allylic CH bond in product olefin is the factor which determines whether or not observable self‐inhibition occurs. Thus, n ‐hexane pyrolysis, whose chain decomposition is terminated by recombination and disproportionation of ethyl, is not significantly self‐inhibited, whereas that of neopentane which is terminated by recombination of methyl is very strongly inhibited because methyl is 14× more reactive than ethyl. The implications for other alkanes are briefly discussed.