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Kinetics and mechanism of gas‐phase pyrolysis of ylides. Part 3. 1 Thermal reactivity of α ‐carbonyl‐ and thiocarbonyl‐stabilized methylenetriphenylphosphoranes
Author(s) -
AlBashir Rasha F.,
AlAwadi Nouria A.,
ElDusouqui Osman M. E.
Publication year - 2011
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.1752
Subject(s) - chemistry , arrhenius equation , reactivity (psychology) , flash vacuum pyrolysis , pyrolysis , kinetics , activation energy , gas phase , atmospheric temperature range , reaction rate constant , reaction mechanism , ketone , photochemistry , organic chemistry , thermodynamics , catalysis , medicine , alternative medicine , physics , pathology , quantum mechanics
Fourteen ketone/thione‐stabilized triphenylphosphonium methylides were subjected to conventional gas‐phase and flash vacuum pyrolysis (FVP). The kinetics of the first‐order thermal gas‐phase reactions of all these compounds were investigated over 360–653 K temperature range. The values of the Arrhenius log A and energy of activation of these ylides averaged 11.52 ± 0.34 s −1 and 133.20 ± 3.14 kJ mol −1 , respectively. The products of sealed‐tube (static) and FVP were analyzed and compared. A mechanism is proposed to account for the products of reaction. The rate constants [ k (s −1 )] of the substrates at 500 K were calculated and used to substantiate the proposed mechanism of pyrolysis, and to rationalize the thermal gas‐phase reactivities of the ylides under study. Copyright © 2010 John Wiley & Sons, Ltd.