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... torate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. (DNNC) and its DNNC-d 6 deuterium labeled analogue were obtained by isothermal differential scanning calorimetry (IDSC) at 142, 145, and 148 o C. Global rate constants and kinetic deuterium isotope effect (KDIE) data from the exothermic decomposition process suggest that homolytic C-H bond rupture, in one or both types of chemically non-equivalent methylene (-CH 2 ) groups of the DNNC ring structure, constitutes the exothermic rate-controlling step. A DNNC-d 6 energy of activation equal to 115 kJ/mole was determined for this initial autocatalytic exothermic energy release from which a 106 kJ/mol activation energy was calculated for unlabeled DNNC. This exothermic autocatalytic decomposition process follows an extended endothermic induction period for DNNC which shows a higher 128 kJ/mole activation energy during which a catalytic initiating species may form by a ratecontrolling step different from C-H bond rupture. Unclassified b. ABSTRACT Unclassified c. THIS PAGE Unclassified A 11 19b. TELEPHONE NUMBER (include area code) (661) 275-5847 Standard Form 298 (Rev. 8-98) Dedicated to the memory of Raymond N. Rogers (Los Alamos National Laboratory), a pioneer in isothermal DSC kinetic analysis, an outstanding scientist, a research mentor, collaborator, and true friend (dec. March 8, 2005)-SAS. Abstract The solid state thermochemical decomposition kinetics and activation energy of neat 1,3,5,5-tetranitrohexahydropyrimidine (DNNC) and its DNNC-d 6 deuterium labeled analogue were obtained by isothermal differential scanning calorimetry (IDSC) at 142, 145, and 148 • C. Global rate constants and kinetic deuterium isotope effect (KDIE) data from the exothermic decomposition process suggest that homolytic C H bond rupture, in one or both types of chemically non-equivalent methylene ( CH 2 ) groups of the DNNC ring structure, constitutes the exothermic rate-controlling step. A DNNC-d 6 energy of activation equal to 115 kJ/mol was determined for this initial autocatalytic exothermic energy release from which a 106 kJ/mol activation energy was calculated for unlabeled DNNC. This exothermic autocatalytic decomposition process follows an extended endothermic induction period for DNNC which shows a higher 128 kJ/mol activation energy during which a catalytic initiating species may form by a rate-controlling step different from C H bond rupture.