Semiempirical molecular orbital estimation of the relative stability of bianthryls produced by anthracene pyrolysis

The pyrolysis of pure anthracene at temperatures between 1200 and 1500 K produced all six bianthryl isomers whose relative yields appear to be related to steric factors. To evaluate the hypothesis that thermodynamic factors govern the product distribution of bianthryls in this system, the relative e...

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Bibliographic Details
Published inCombustion and flame Vol. 94; no. 3; pp. 233 - 243
Main Authors Mulholland, J.A., Mukherjee, J., Wornat, M.J., Sarofim, A.F., Rutledge, G.C.
Format Journal Article
LanguageEnglish
Published New York, NY Elsevier Inc 01.08.1993
Elsevier Science
Subjects
02 PETROLEUM
020400 - Petroleum- Processing
ANTHRACENE
Applied sciences
AROMATICS
CALCULATION METHODS
CHEMICAL REACTION KINETICS
CHEMICAL REACTION YIELD
CHEMICAL REACTIONS
CONDENSED AROMATICS
DECOMPOSITION
Energy
ENTHALPY
ENTROPY
Exact sciences and technology
Fuel processing. Carbochemistry and petrochemistry
Fuels
HYDROCARBONS
ISOMERS
KINETICS
MOLECULAR ORBITAL METHOD
ORGANIC COMPOUNDS
PHYSICAL PROPERTIES
PYROLYSIS
REACTION KINETICS
Solid fuel processing (coal, coke, brown coal, peat, wood, etc.)
STABILITY
STEREOCHEMISTRY
THERMOCHEMICAL PROCESSES
THERMODYNAMIC PROPERTIES
THERMODYNAMICS
YIELDS
Molecular orbital
Pyrolysis
Anthracene
Stability
Steric effect
Semiempirical method
Modeling
Radical
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Summary:The pyrolysis of pure anthracene at temperatures between 1200 and 1500 K produced all six bianthryl isomers whose relative yields appear to be related to steric factors. To evaluate the hypothesis that thermodynamic factors govern the product distribution of bianthryls in this system, the relative enthalpies and entropies of biaryl isomers were estimated by molecular orbital modeling, using the semiempirical AM1 (Austin Model 1). Computational analysis of several isomer sets demonstrates that the relative stabilities of a large number of biaryl isomers are determined largely by steric interactions caused by structural features defined as bays, coves, and fjords. These steric factors affect both the degree of biaryl twist in the preferred conformation and the freedom of internal rotation. Molecular orbital modeling supports the hypothesis that a thermodynamic distribution of bianthryl isomers is produced by anthracene pyrolysis.
ISSN:0010-2180
1556-2921
DOI:10.1016/0010-2180(93)90070-J