Kinetics of OH reactions with N2H4, CH3NHNH2 and (CH3)2NNH2 in the gas phase

✍ Scribed by Ghanshyam L. Vaghjiani

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 149 KB
• Volume: 33
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.1029

✦ Synopsis

Abstract

The gas phase reaction kinetics of OH with three di‐amine rocket fuels—N~2~H~4~, CH~3~NHNH~2~, and (CH~3~)~2~NNH~2~—was studied in a discharge flow tube apparatus and a pulsed photolysis reactor under pseudo‐first‐order conditions in [OH]. Direct laser‐induced fluorescence monitoring of the [OH] temporal profiles in a known excess of the [diamine] yielded the following absolute second‐order OH rate coefficient expressions; k~1~ = (2.17 ± 0.39) × 10^−11^ e^(160±30)/T^, k~2~ = (4.59 ± 0.83) × 10^−11^ e^(85±35)/T^ and k~3~ = (3.35 ± 0.60) × 10^−11^ e^(175±25)/T^ cm^3^ molec^−1^ s^−1^, respectively, for reactions with N~2~H~4~, CH~3~NHNH~2~ and (CH~3~)~2~NNH~2~ in the temperature range 232–637 K. All three reactions did not show any discernable pressure dependence on He or N~2~ buffer gas pressure of up to 530 torr. The magnitude of the weak temperature and the lack of pressure effects of the OH + N~2~H~4~ reaction rate coefficient suggest that a simple direct metathesis of H‐atom may not be important compared to addition of the OH to one of the N‐centers of the diamine skeleton, followed by rapid dissociation of the intermediate into products. Our findings on this reaction are qualitatively consistent with a previous ab initio study [3]. However, in the alkylated diamines, direct H‐abstraction from the methyl moiety cannot be completely ruled out. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 354–362, 2001