Thermochemistry of organosilicon compounds VII. Permethylcyclosilazanes and 1,1,3,3-tetramethyldisilazane

The enthalpy of formation (ΔH_f⁰), enthalpy of evaporation (ΔH_v⁰) and enthalpy of atomization (ΔH_a) 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.     

Specific features of vulcanization of unsaturated rubbers with polymeric <Emphasis Type="Italic">p</Emphasis>-dinitrosobenzene

Conditions of vulcanization of unsaturated rubbers were studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1722–1724.Original Russian Text Copyright ¢ 2004 by Zaikov, Klyuchnikov, Makarov, Deberdeev.     

Synthesis of 1,3,5-trinitrosobenzene

Russian Chemical Bulletin -