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The Pyrolysis of 3‐Picoline: Ab Initio Quantum Chemical and Experimental (Shock Tube) Kinetic Studies
Author(s) -
Jones Jeffrey,
Bacskay George B.,
Mackie John C.
Publication year - 1996
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199600034
Subject(s) - chemistry , ab initio , picoline , cyanoacetylene , shock tube , acetylene , radical , kinetic energy , benzene , pyridine , pyrolysis , reaction rate constant , computational chemistry , kinetics , thermodynamics , organic chemistry , shock wave , molecule , physics , quantum mechanics
The pyrolysis of 3‐picoline dilute in argon was investigated using a single‐pulse shock tube over the temperature range of 1400–1650 K and total pressures of 12–13 atm. The principal products observed were HCN, acetylene, benzene, cyanoacetylene, methane, and pyridine. Assuming that 3‐picoline decomposes according to first‐order kinetics, the rate constant for its overall disappearance was determined to be k dis = 10 16.9 (±0.8) exp[–99 (±6) kcal mol −1 /RT ] s −1 . The principal initial decomposition routes were found to be via the formation of the 3‐picolyl and m ‐pyridyl radicals whose subsequent ring‐opening led to the observed products. A 68‐step kinetic model was developed that successfully fits the experimental data. The dominant reactions, i.e., the formation of picolyl and pyridyl radicals and their subsequent chain‐opening reactions, were studied using ab initio quantum chemical techniques. The ab initio data were also incorporated into the kinetic model in the form of energies and A‐factors for reactions for which no kinetic or thermochemical data were previously available. Optimization of the kinetic model yields a value of 64 ± (3) kcal mol −1 for the heat of formation of 3‐picolyl, a value lower than that for 2‐picolyl, suggesting that the decomposition of 3‐picoline more closely resembles that of toluene, rather than its isomer 2‐picoline.