Kinetic Studies of the Reactions of Alkyl and Silyl Hydrides Page: 3
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Yuan, Jessie, Kinetic Studies of the Reactions of Alkvl and Silvl Hydrides. Doctor
of Philosophy (Chemistry), August, 1996, 125 pp., 25 tables, 20 illustrations, references,
134 titles.
The Kinetics of the reactions involving alkyl and silyl hydrides were studied by the
flash photolysis / resonance fluorescence technique.
The reactions of alkyl radicals (R = C2H5, i-C3H7, t-C4H9) with HBr have been
studied at room temperature and the rate constants obtained (units are in cm s ) are: k3
3.3
= (7.01 ± 0.15) x 10"12, k32 = (1.25 ± 0.06) x 10"11, k31 = (2.67 ± 0.13) x 10"n These
results, combined with previously determined reverse rate constants and other kinetic
information, yield bond dissociation enthalpies (units in kJ mol"1) at 298 K : primary C-H
in C2H5-H (423 .6 ± 2), secondary C-H in i-C3H7-H (409.9 ± 2), tertiary C-H in t-C^-H (
405.1 ± 2). These rate constants and bond energies are in good agreement with previous
results. Temperature-dependent rate constants for n-C3H7 + HBr, Si(CH3)3 + HBr, and Br
+ Si2H6 were obtained in the following temperature ranges and the Arrhenius expression
for each reaction (A / (cm3 s"1), Ea / (kJ mol"1)) are: k34 = (6.19 ± 1.12) x 10"13 exp (7.14
± 0.58 / RT), 296 -520 K; k3.6 = (8.1 ± 2.0) x 10'12 exp (5.12 ± 0.72 /RT), 289 - 515 K;
k38 = (1.35 ± 0.12) x 10"10 exp (-3.05 ± 0.3 / RT), 295 - 556 K. The bond energies (kJ
mol"1) derived for primary C-H in n-C3H7-H, tertiary Si-H in Si(CH3)3-H, and primary Si-H
in Si2H5-H are: 425.3 ± 3, 397.8 ± 2, and 371.9 ± 5, respectively. These bond strength
determinations confirm that the methyl group decreases the C-H bond strength in alkanes,
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Yuan, Jessie (Jessie Win-Jae). Kinetic Studies of the Reactions of Alkyl and Silyl Hydrides, dissertation, August 1996; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc277864/m1/3/: accessed July 18, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .