72282-90-7Relevant academic research and scientific papers
Kinetics of Cyclopropyl Radical Reactions. 3. Study of Some 1-Substituted Cyclopropyl Radicals by EPR Spectroscopy. The Inversion Barrier for 1-Methylcyclopropyl
Deycard, S.,Hughes, L.,Lusztyk, J.,Ingold, K. U.
, p. 4954 - 4960 (2007/10/02)
The 1-methyl-, 1-ethoxy-, and 1-chlorocyclopropyl radicals have been observed by low-temperature EPR spectroscopy in "frozen" configurations in which the ring hydrogens that are syn and anti to the unpaired elecron's orbital have different hyperfine splittings.The aH(syn)/aH(anti) ratios are 1.5 (CH3), 1.8 (EtO), and 1.9 (Cl), all considerably lower than the ratio of ca. 3.3 found by Kawamura et al. for methyl-substituted 1-fluorocyclopropyl radicals.The out-of-plane angles of the 1-substituent have been calculated from measured a13Cα values to be 22.5 deg (cyclopropyl), 22.9 deg (CH3), 29.1 deg (EtO), and 5.8 deg (MeSi).These angles are considerably smaller than those that have been calculated for some of these radicals by ab initio and other methods.Variable-temperature EPR spectroscopy on 1-methylcyclopropyl yields the following Arrhenius equation for its inversion: log (kinv/s-1) = (13.1 +/- 0.3) - (3.1 +/- 0.2)/2.3RT kcal/mol.For 1-ethoxycyclopropyl the rate constant for rotation about the .C-OEt bond can be represented by log (krot/s-1) = (12.5 +/- 0.2) - (5.8 +/- 0.2)/2.3RT.The barrier to inversion of this radical is >/= 9 kcal/mol.The 1-chlorocyclopropyl radical could only be observed at very low temperatures.
Evidence Suggesting the Occurrence of Cycloaddition Products in the Ion/Molecule Reactions of Suitably Substituted Allyl Cations and Olefins
Tilborg, M. W. E. M. van,Doorn, R. van,Nibbering, N. M. M.
, p. 152 - 156 (2007/10/02)
The ion/molecule reactions of allyl cations and 2-methoxyallyl cations with vinyl methyl ether, 1-chloro-2-ethoxyethene and 1,2-dimethoxyethene are discussed in terms of cycloaddition reactions.Deuterium labelling of the cations has been used for the study of the reaction mechanisms.The appearance of various product ions in these ion/molecule reactions lead to the suggestion that in reactions of allyl cations with alkenes non-cyclic + product ions are formed preferentially, but that in reactions of 2-methoxyallyl cations with alkenes a significant part of the product ions are methoxycyclopentadienyl cations.These observations are ascribed to the stabilizing effect of the methoxy group with regard to the positive charge in the product ions.
