- Photochemical Hydroxymethylation of Alicyclic and Aliphatic Alkenes Induced by a EuIII/EuII Photoredox System in Methanol
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The photoirradiation of a methanol solution of EuCl3 and alkenes such as cyclohexene, cyclooctene, cyclododecene, and tetramethylene afforded (hydroxymethyl)alkane.The dihydro dimer of alkene,hydrogen, and ethylene glycol are also formed.Reactions proceed via a radical mechanism induced by hydrogen atoms and hydroxymethyl radicals, which are produced by a photoredoc reaction of EuIII/EuII in methanol.
- Ishida, Akito,Yamashita, Shinya,Toki, Susumu,Takamuku, Setsuo
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p. 1195 - 1200
(2007/10/02)
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- Thermolabile Hydrocarbons, XIV. Thermal Stability, Strain Enthalpy, and Structure of sym. Hexaalkyl-substituted Ethanes
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Activation parameters were determined for the thermolysis reaction of thirteen sym. hexaalkyl-substituted ethanes (Cq-Cq-series).From product analyses it was concluded that the central Cq-Cq-bond is cleaved in the rate determining step by homolysis.A reasonable relationship between the free enthalpy of activation ΔG* (300 deg C) of the reactions and steric substituent constants φfwas observed.Much better correlations were found between ΔG* (300 deg C) and strain enthalpies HS of the hydrocarbons as obtained from molecular mechanics calculations.From the slope of these correlations it is deduced that 40percent residual strain is still present at transition state of these C-C-cleavage reactions.The structural data calculated using Allinger's MM2 force field are distinguished by long central Cq-Cq-bonds (up to 164.1 pm), by large angle deformations on α-C-atoms of side chains and by deviations from the ideal torsional angle Θ = 180 deg along the central bond.The central Cq-Cq-bond length increases in a linear manner with increasing strain enthalpy HS.
- Winiker, Robert,Beckhaus, Hans-Dieter,Ruechardt, Christoph
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p. 3456 - 3476
(2007/10/02)
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