4249-09-6Relevant academic research and scientific papers
Chemistry of gem-Dihalocyclopropanes. XXI. An Example of Competition between 1,3-Insertion and the Vinylcyclopropylidene/Cyclopentenylidene Rearrangement
Brun, Roger,Grace, David S. B.,Holm, Kjetil H.,Skatteboel, Lars
, p. 21 - 25 (2007/10/02)
gem-Dibromotrimethylvinylcyclopropane was treated with ethereal methyllithium at four temperatures ranging from -78 deg C to +20 deg C.At -40 deg C or higher, 1,5,5-trimethylcyclopentadiene was formed as the main product along with three isomeric bicyclobutanes; the ratio was practically independent of temperature.The compounds are believed to originate from the same intermediate cyclopropylidene by a carbene-carbene rearrangement and 1,3-insertion reactions, respectively.At -78 deg C a substantial amount of dimers was formed as well, indicating an unusual stabilization of the intermediate α-bromo lithium derivative.No allene was detected in any of the reactions.Possible factors that govern the product distribution are discussed.
Electronic Effects of Polar Substituents in the Gas Phase Unimolecular Elimination of 4-Substituted Isobornyl Acetates
Chuchani, Gabriel,Hernandez A, Jose A.,Morris, David G.,Shepherd, Alistair G.
, p. 917 - 922 (2007/10/02)
The rates of gas-phase elimination of a series of 4-substituted isobornyl acetates have been measured in the presence of propene between 209-370 deg C and within a pressure range 37-153 Torr; a static system with seasoned vessels was used.The reaction are unimolecular, homogeneous, and obey a first-order rate law; electron-withdrawing substituents at C(4) cause a diminution in the elimination rate, such that ρ1 -0.69 in a Hammett treatment.The temperature dependence of the rate coefficients is illustrated for the Arrhenius equation for isobornyl acetate: logk/s-1=(12.82+/-0.13)-(189.2+/-1.5)kJmol-1/2.303RT.The results are consistent with a cyclic transition state in which C(2)-O cleavage is more advanced than that of C(3)-H.The major primary product of elimination of isobornyl acetate is bornylene, which partially isomerises to camphene and tricyclene under the reaction conditions.Bornylene also undergoes a retro-Diels-Alder reaction to yield the trimethylcyclopentadiene and ethylene.
