Pyrolysis of α-carbonyl-substituted cycloalkyl phenyl sulphoxides

• Published in: Journal of analytical and applied pyrolysis 1987, Vol.12 (3), p.257-263
• Main Authors: Tsukurimichi, Eiichi, Yoshimura, Toshiaki, Takahashi, Ritsuko, Wakisaka, Yuhko
• Format: Article
• Language: English
• Subjects: 2-oxo-3-methylcyclohexyl phenyl sulphoxide; 2-oxocyclohexyl phenyl sulphoxide; Chemistry; Ethyl phenyl sulphoxide; Exact sciences and technology; Kinetics and mechanisms; kinetics, reaction; Organic chemistry; pyrolysis; reaction mechanism; Reactivity and mechanisms
• ISSN: 0165-2370; 1873-250X
• DOI: 10.1016/0165-2370(87)85005-2

The effect on the pyrolysis of the carbonyl group substituted at the α-position in the S-cycloalkyl ring in cycloalkyl phenyl sulphoxides was investigated by using 2-oxocyclohexyl phenyl sulphoxide ( 1) and 2-oxo-3-methylcyclohexyl phenyl sulphoxide ( 2). The rates of reaction were correlated with a first-order kinetic equation ( r = 0.999). A very large rate enhancement in the pyrolysis of ( 1) and ( 2) was observed in comparison with that of ethyl phenyl sulphoxide ( 3), namely, the relative rates of ( 1) and ( 2) were about 2100 and 1600 times larger than that of ( 3), respectively. The activation energies calculated for ( 1) and ( 2) were 108 and 109 kJ/mol, respectively, and their activation entropies were both ca. −11 J K −1 mol −1. A solvent effect on the pyrolysis was not observed, as in the pyrolysis of other sulphoxides. From the results, it was concluded thatthe rate enhancement on substituting a carbonyl group was due to mainly the conjugative effect of the carbonyl group with the double bond developed in the transition state during the pyrolysis.