Gas Phase Reaction Kinetics of O-Atoms with (CH3)2NNH2, CH3NHNH2 and N2H4, and Branching Ratios of the OH Product
Abstract
The gas phase reaction kinetics of O-atoms with the two alkylated di-amine rocket fuels (CH3)2NNH2 and CH3NHNH2 was studied in a discharge flow-tube apparatus under pseudo first-order conditions in O-atom. Direct vuv cw-resonance fluorescence monitoring of the O-atom temporal profiles in a known excess of the DI-AMINE yielded the following absolute second-order O-atom rate coefficient expressions; k(sub j) = (1.94 + or - 0.34) x 10(exp -11) e(25 + or - 25)/T and k2 = (2.29 + or - 0.40) x 10(exp -11) e(-145 + or - 40)/T cu cm molec(exp -1) s(exp -1), respectively, for reactions with (CH3)2NNH2 and CH3NHNH2 in the temperature range 232-644 K and in He pressure of 2.0 torr. The total yields of OH in the reactions were measured to be (0.12 + or - 0.09) and (0.14 + or - 0.10) at 298 K and in 2.0 torr He pressure. Close to approx. 53% and approx. 59% of the OH produced was estimated to be vibrationally excited. A pulsed-photolysis reactor was used to extend our measurements on the O-atom reaction kinetics with the unsubstituted rocket fuel N2H4 that we had previously studied in the flow-tube apparatus. At 298 K, both the rate coefficient, k3 = (0.59 = or - 0.12) x 10(exp -11) cu cm/ molec s and the total OH yield = (0.35 + or - 0.14) did not show any discernable dependence on He or N2 buffer gas pressures of up to 404 torr. The magnitude of the weak temperature dependence and the lack of pressure effects in the O + N2H4 reaction rate coefficient suggests that simple direct metathesis of H-atom may not be important compared to initial addition of the O-atom to the di-amine, followed by rapid dissociation of the intermediate into a variety of products.
Document Details
- Document Type
- Technical Report
- Publication Date
- Mar 16, 2001
- Accession Number
- ADA410221
Entities
People
- Ghanshyam L Vaghjiani