Thermochemistry of organosilicon compounds VII. Permethylcyclosilazanes and 1,1,3,3-tetramethyldisilazane |
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Authors: | M. G. Voronkov V. A. Klyuchnikov L. I. Marenkova |
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Affiliation: | a Institute of Organic Chemistry, Siberian Division, Russian Academy of Sciences, 664033, Irkutsk, Russia b Kemerovo State Medical Institute, 650027, Kemerovo, Russia |
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Abstract: | The enthalpy of formation (ΔHf0), enthalpy of evaporation (ΔHv0) and enthalpy of atomization (ΔHa) of permethylcyclosilazanes (Me2SiNH)n (n = 3, 4) and 1,1,3,3-tetramethyldisilazane (Me2SiH)2NH have been determined. The enthalpies of formation of these compounds were compared with those calculated by the Benson-Buss-Franklin and Tatevskii additive schemes. In higher permethylcyclosilazanes the energy of the endocyclic Si---N bond is 306 ± 2 kJ mol−1 (73 kcal mol−1), that is 12 ± 2 kJ mol−1 (3 kcal mol−1) lower than the energy of the acyclic Si---N bond. The strain energy of the cyclotrisilazane ring is estimated to be 10.5 kJ mol−1 (2.5 kcal mol−1), whereas the energy of the ring Si---N bond is 295 kJ mol−1 (70.5 kcal mol−1). The thermochemical data for permethylcyclosilazanes were compared with the corresponding values for permethylcyclosiloxanes calculated from the results of previously reported studies. |
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Keywords: | Silicon Thermochemistry Bond energy Enthalpy of formation Permethylcyclosilazanes Permethylcyclosiloxanes |
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