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Free‐radical reactions of cyclic ethers and sulfides with bromotrichloromethane
Author(s) -
Hallen Richard T.,
Gleicher Gerald Jay,
Mahiou Belaid,
Clapp Gary E.
Publication year - 1989
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.610020502
Subject(s) - chemistry , reactivity (psychology) , heteroatom , ring strain , tetrahydrofuran , hydrogen atom abstraction , ring (chemistry) , medicinal chemistry , hydrogen atom , sulfur , thermal decomposition , stereochemistry , photochemistry , hydrogen , organic chemistry , medicine , alkyl , solvent , alternative medicine , pathology
The relative rates of hydrogen atom abstraction from a series of twelve saturated cyclic ethers and sulfides were determined at 70°C. The abstracting radical could be generated from bromotrichloromethane both photolytically or by the thermal decomposition of AIBN. The reaction rates did not show a dependence upon method of radical generation. Reaction occurred only at the position adjacent to the heteroatom. The reactivity of the cyclic ethers was in the order C 4 H 8 O > C 6 H 12 O > C 3 H 6 O > C 5 H 10 O. This trend would indicate appreciable influence by ring strain, however, the slightly greater reactivity of tetrahydrofuran relative to oxepane suggests a contribution by stereoelectronic factors as well. The reactivity of the cyclic sulfides, which reacted faster than the corresponding ethers, was in the order C 4 H 8 S > C 5 H 10 S > C 6 H 12 S. This would imply little influence of ring strain. The major structural effect would be that of variable electron donating ability of the sulfur atom. The rate of reaction of thietane was also determined. It was found to preferentially undergo S H 2 attack at the sulfur atom followed by ring opening rather than hydrogen abstraction. The reactivities of both series of compounds were decreased by the inductive effect of a second heteroatom beta to the reaciton site.