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Maximally inhibited elimination of kinetics of (2‐bromoethyl)benzene and 1‐bromo‐3‐phenylpropane in the gas phase. Anchimeric assistance of the phenyl group
Author(s) -
Chuchani Gabriel,
Martin Ignacio
Publication year - 1990
Publication title -
journal of physical organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.325
H-Index - 66
eISSN - 1099-1395
pISSN - 0894-3230
DOI - 10.1002/poc.610030203
Subject(s) - chemistry , arrhenius equation , benzene , cyclohexene , kinetics , torr , medicinal chemistry , reaction rate constant , propene , atmospheric temperature range , stereochemistry , photochemistry , thermodynamics , activation energy , organic chemistry , catalysis , physics , quantum mechanics
The gas‐phase elimination kinetics of (2‐bromoethyl)benzene and 1‐bromo‐3‐phenylpropane were studied in a static system and seasoned vessels over the temperature range 390–450 °C and the pressure range 32–104 Torr. The reactions, under maximum inhibition of 4‐fold pressure of the free‐radical suppressor cyclohexene and/or propene, are homogeneous, unimolecular and obey a first‐order rate law. The rate coefficients are given by the following Arrhenius equations: for (2‐bromoethyl)benzene, log k 1 (s −1 ) = (13·04 ± 0·10) − (210·8 ± 1·3) kJ mol −1 (2·303 RT ) −1 , and for 1‐bromo‐3‐phenylpropane, log k 1 (s −1 ) = (14·09 ± 0·27) − (227·7 ± 3·6) kJ mol −1 (2·303 RT ) −1 . The phenyl group of (2‐bromoethyl)benzene appears to provide anchimeric assistance in the HBr elimination of this compound. However, neighbouring C 6 H 5 participation at the 3‐position in 1‐bromo‐3‐phenylpropane for a C‐4 conformation is apparently absent. The mechanisms of these reactions are discussed.