High-temperature collisional energy transfer in highly vibrationally excited molecules II: Isotope effects in isopropyl bromide systems

✍ Scribed by Trevor C. Brown; Keith D. King; Robert G. Gilbert

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 881 KB
• Volume: 19
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.550190906

✦ Synopsis

Values for (AEduwn), the average downward energy transferred from the reactant to the bath gas upon collision, have been obtained for highly vibrationally excited undeuterated and per-deuterated isopropyl bromide with the bath gases Ne, Xe, C,H,, and C,D,, a t ca. 870 K. The technique of pressure-dependent very low-pressure pyrolysis IVLPP) was used to obtain the data. For C3H,Br, the (AEdorn) values (cm-') are 490 (Ne), 540 (XeJ, 820 iC,H,), and 740 (C,D,), and for C3DiBr, 440 (Ne), 570 iXe), 730 iC2H,), and 810 (C,D,). The uncertainties in these values are ca. +10%. The (AEdoan) values for the inert bath gases Ne and Xe show excellent agreement with the theoretical predictions of the semi-empirical biased random walk model for monatomic/substrate collisional energy exchange [J. Chem. Phys., 80,5501 (198411. The relative effects of deuteration of the reactant molecule on (AEdown) also compare favorably with the predictions of this theoretical model. Extrapolated high-pressure rate coefficients (s -') for the thermal decomposition of reactant are 10'36r03 exp(-200 2 8 kJ mol-'/RT) for C3H,Br and 10''y."~ exp(-207 ? 8 k J mol-'/RT) for C3D7Br, which are consistent with previous studies and the expected isotope effect.