15840-64-9Relevant articles and documents
Acid-Catalyzed Olefin-Alcohol Interconversion in the 1-Methylcyclooctyl System. Strain-Relief Acceleration of the Hydration of 1-Methyl-trans-cyclooctene
Chiang, Y.,Chwang, W. K.,Kresge, A. J.,Powell, M. F.,Szilagyi, S.
, p. 5218 - 5224 (1984)
Rates of reaction with aqueous perchloric acid at 25 deg C have been measured for 1-methyl-cis-cyclooctene, 1-methyl-trans-cyclooctene, and their exo isomer, methylenecyclooctane.The only products formed to any significant extent in each of these reactions are 1-methylcyclooctanol and the cis-cycloalkene, but both the trans- and exo-olefins give these products in initially noneequilibrium proportions: / = 1.27 +/- 0.05 at equilibrium, 15.1 +/- 0.9 from the trans-olefin and 0.44 +/- 0.05 from the exo-olefin.This is taken as evidence for the existence of two conformationally different 1-methylcyclooctyl carbocationic intermediates in these reactions, an unstable crown (or twist) cation formed by protonation of the trans-olefin and a (conformationally) stable boat-chair cation formed from the other two olefins and the alcohol.The barrier for interconversion of these two cations is estimated at ΔG(excit.) = 5.3 +/- 0.6 kcal mol-1.The barrier for hydration of either cation to the alcohol is also estimated, by two different methods, at ΔG(excit.) = 3.6 +/- 0.6 kcal mol-1 or 4.3 +/- 0.3 kcal mol-1.The smallness of these barriers suggests that the reaction of tertiary aliphatic carbocations with water in aqueous solution is an essentially unactivated process.These estimates plus the rate and equilibrium constants measured here allow nearly complete free energy characterization of the 1-methylcyclooctyl system.The rates of reaction of the cis- and exo-olefin with the hydronium ion are normal, but strain relief accelerates the rate of the trans-cycloalkene by a factor of 18500.
Electrophilic Cleavage of Cyclopropanes. Acetolysis of Bicyclic and Tricyclic Cyclopropanes
Wiberg, Kenneth B.,Kass, Steven R.,Meijere, Armin de,Bishop, K. C.
, p. 1003 - 1007 (2007/10/02)
The acetolysis of a series of bicycloalkanes and propellanes has been studied.The effect of ring strain, caused by changing ring size or introducing a trans-ring fusion, on the rate and products of the reaction has been examined.No correlation was found between rates of acetolysis and strain energy relief, but with the exception of propellane, there is a rough correlation with ionization potentials.The degree of polarization of the C-C bonds in the presence of a proton correlates very well with reactivity and is a controlling factor for the acetolysis rates.The importance of the energies of unoccupied orbitals with the appropriate symmetry in controlling electron polarization is shown by the large difference in rate of reaction between - and propellanes.
