کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
5375548 | 1504307 | 2008 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Kinetics of the R + HBr â RH + Br (CH3CHBr, CHBr2 or CDBr2) equilibrium. Thermochemistry of the CH3CHBr and CHBr2 radicals
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
چکیده انگلیسی
The kinetics of the reaction of the CH3CHBr, CHBr2 or CDBr2 radicals, R, with HBr have been investigated in a temperature-controlled tubular reactor coupled to a photoionization mass spectrometer. The CH3CHBr (or CHBr2 or CDBr2) radical was produced homogeneously in the reactor by a pulsed 248 nm exciplex laser photolysis of CH3CHBr2 (or CHBr3 or CDBr3). The decay of R was monitored as a function of HBr concentration under pseudo-first-order conditions to determine the rate constants as a function of temperature. The reactions were studied separately from 253 to 344 K (CH3CHBr + HBr) and from 288 to 477 K (CHBr2 + HBr) and in these temperature ranges the rate constants determined were fitted to an Arrhenius expression (error limits stated are 1Ï + Student's t values, units in cm3 moleculeâ1 sâ1, no error limits for the third reaction): k(CH3CHBr + HBr) = (1.7 ± 1.2) Ã 10â13 exp[+ (5.1 ± 1.9) kJ molâ1/RT], k(CHBr2 + HBr) = (2.5 ± 1.2) Ã 10â13 exp[â(4.04 ± 1.14) kJ molâ1/RT] and k(CDBr2 + HBr) = 1.6 Ã 10â13 exp(â2.1 kJ molâ1/RT). The energy barriers of the reverse reactions were taken from the literature. The enthalpy of formation values of the CH3CHBr and CHBr2 radicals and an experimental entropy value at 298 K for the CH3CHBr radical were obtained using a second-law method. The result for the entropy value for the CH3CHBr radical is 305 ± 9 J Kâ1 molâ1. The results for the enthalpy of formation values at 298 K are (in kJ molâ1): 133.4 ± 3.4 (CH3CHBr) and 199.1 ± 2.7 (CHBr2), and for α-C-H bond dissociation energies of analogous compounds are (in kJ molâ1): 415.0 ± 2.7 (CH3CH2Br) and 412.6 ± 2.7 (CH2Br2), respectively.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Chemical Physics - Volume 351, Issues 1â3, 3 July 2008, Pages 141-146
Journal: Chemical Physics - Volume 351, Issues 1â3, 3 July 2008, Pages 141-146
نویسندگان
Jorma A. Seetula, Arkke J. Eskola,