5171-86-8Relevant academic research and scientific papers
Enthalpies of Formation of Hexaethylethane, Octamethylhexane, and Tri-tert-butylmethane. Extremely Strained Hydrocarbons
Verevkin, Sergey P.,N?lke, Margot,Beckhaus, Hans-Dieter,Rüchardt, Christoph
, p. 4683 - 4686 (1997)
3,3,4,4-Tetraethylhexane (1) and 2,2,3,3,4,4,5,5-octamethylhexane (2) were synthesized from 3-ethylpentane and 2,2,3-trimethylbutane, respectively, by UV-irradiation with mercury in the gas phase. The enthalpies of combustion ΔHc° of 1, 2, and tri-tert-butylmethane (3) when measured calorimetrically were ΔHc° = -9467.2 ± 2.3, -9491.4 ± 2.3, and -8825.0 ± 4.3 kJ·mol-1, respectively. The enthalpies of vaporization of 1 and 2 and the enthalpy of sublimation of 3 were derived from the temperature dependence of their vapor pressures. The latter were determined by a flow method. The resulting standard enthalpies of formation were ΔHf° (g) = -265.5 ± 2.6, -248.3 ± 2.4, and -235.2 ± 4.3 kJ·mol-1 for 1, 2, and 3, respectively. They correspond to strain enthalpies (Hs) of 118.1, 177.2, and 156.1 kJ·mol-1, respectively, These values provide valuable test cases for semiempirical and empirical calculations.
Thermolabile Hydrocarbons, XIV. Thermal Stability, Strain Enthalpy, and Structure of sym. Hexaalkyl-substituted Ethanes
Winiker, Robert,Beckhaus, Hans-Dieter,Ruechardt, Christoph
, p. 3456 - 3476 (2007/10/02)
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.
