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Kinetics and mechanism of thermal gas‐phase elimination of α‐substituted carboxylic acids: role of relative basicity of α‐substituents and acidity of incipient proton
Author(s) -
AlAwadi Nouria A.,
Kaul Kamini,
ElDusouqui Osman M. E.
Publication year - 2000
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 - 10.1002/1099-1395(200009)13:9<499::aid-poc269>3.0.co;2-0
Subject(s) - chemistry , arrhenius equation , thiophenol , catalysis , aniline , pyrolysis , kinetics , medicinal chemistry , reaction mechanism , phenol , reaction rate constant , organic chemistry , activation energy , physics , quantum mechanics
2‐Phenoxypropanoic acid together with five of its aryl derivatives, its phenylthio and its N ‐phenylamino analogues were pyrolyzed at 494–566 K. The reactions were homogeneous, polar and free from catalytic and radical pathways, and obeyed a first‐order rate equation. The limits of the Arrhenius log A (s −1 ) and E (kJ mol −1 ) values obtained for these reactions averaged 11.98 ± 1.71 and 158.1 ± 17.4, respectively. Analysis of the pyrolysates showed the elimination products to be carbon monoxide, acetaldehyde and the corresponding phenol, thiophenol or aniline compounds. The pyrolysis of 2‐phenoxy‐ and 2‐( N ‐phenylamino)‐1‐propanol was also investigated over the temperature range 638–792 K. The kinetic results and products analysis lend support to a reaction pathway involving a five‐membered cyclic polar transition state. Copyright © 2000 John Wiley & Sons, Ltd.