98775-15-6Relevant academic research and scientific papers
Dynamics of Internal Rotation in 2-(Cycloalkenyl)ethyl Radicals
Walton, John C.
, p. 1809 - 1814 (2007/10/02)
2-(Cycloalkenyl)ethyl radicals having C4 to C7 rings were observed by e.s.r. spectroscopy.The barriers to rotation about the -Cβ bonds were determined from the temperature variation of the β-hydrogen hyperfine splitting and shown to decrease with increasing ring size.In all cases, the preferred conformation about the Cβ-Cγ bond was found to be the one in which the -Cβ bond makes an angle of 90 deg with the plane of the ring.Exchange broadening due to restricted rotation about the Cβ-Cγ bond was observed and the rotation barriers were determined for the radicals with C6 and C7 rings.The radicals were studied using the semi-empirical MINDO/3 and MNDO methods and the corresponding hydrocarbons were investigated by the MM2 force field approach.The variation in the rotational barrier heights were attributed to steric effects.
Hydrogen Abstraction from Spiroalkanes
Roberts, Charles,Walton, John C.
, p. 841 - 846 (2007/10/02)
Hydrogen abstraction from spirohexane by t-butoxyl radicals gave spirohex-2-yl radicals; their rearrangement to cyclobutenylethyl radicals was followed by kinetic e.s.r. spectroscopy.Hydrogen abstraction at the methylene groups adjacent to the cyclopropyl rings in higher spiroalkanes gave spiroalk-2-yl radicals, which rearranged to cycloalkenylethyl radicals too rapidly for detection, together with secondary radicals from abstraction at the other methylene groups in the larger ring.From the measured concentrations of the cycloalkenylethyl and secondary radicals the rate of hydrogen abstraction at the cpm sites relative to the rate of hydrogen abstraction at the secondary sites was determined; significant activation of the cpm hydrogens was found.This activation was attributed to a pseudo-allyl type of effect, i.e., to delocalisation of the unpaired electron into the Walsh orbitals of the cyclopropane ring of the spiroalk-2-yl radicals; semi-empirical SCF-MO calculations supported this explanation.Photobromination of spirohexane occured mainly by SH2 attack of bromine atoms at the cyclopropane methylene carbons with fission of either C-C bond.
