Thermal decomposition of 2,2-bis(difluoroamino) propane studied by FTIR spectrometry and quantum chemical calculations:: the primary dissociation kinetics and the mechanism for decomposition of the (CH3)2CNF2 radical

The kinetics of the thermal decomposition of 2,2-bis(difluoroamino) propane (BDFP) has been studied by pyrolysis/FTIR spectrometry at temperatures between 528 and 553 K using toluene as radical scavenger. The disappearance of BDFP was found to follow the first-order kinetics with the rate constant, k(1) = 10(16.0+/-0.7) exp [ - (24200 +/- 840) / T] s(-1), which agrees closely with the expression obtained by Fokin et al. [Dokl. Akad. Nauk. 332 (1993) 7351, k(1) = 10(15.60) exp(-23600/T) s(-1). The measured large A-factor supports the earlier conclusion that the primary fragmentation process corresponds to the breaking of one of the two NF2 groups. The measured activation energy is also consistent with the predicted first C-N bond dissociation energy, 44-48 kcal/mol, by the hybrid density-functional theory and that evaluated by variational RRKM calculations fitting the observed rate constant, 47.9 kcal/mol. The 2-difluoroamino propyl radical, (CH3)(2)CNF2, was predicted to be thermally unstable, producing readily F atoms and HF molecules via the (CH3)(2)CFNF intermediate. The quantum-chemically predicted mechanisms for the fragmentation of (CH3)(2)C(NF2)(2) and (CH3)(2)CNF2 agree with the product distribution reported by Ross and coworkers [J. Am. Chem. Soc. 94 (1972) 87761. (C) 2002 Elsevier Science B.V. All rights reserved.