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Reactivity of Tris(trimethylsilyl)silane Toward Diarylaminyl Radicals

Reactivity of Tris(trimethylsilyl)silane Toward Diarylaminyl Radicals

V T Varlamov, E T Denisov, C Chatgilialoglu

J Org Chem. 2001 Sep 21;66(19):6317-22.

PMID: 11559181

Abstract:

Absolute rate constants for the reaction of tri-tert-butylphenoxyl radical (ArO*) with (TMS)(3)SiH were measured spectrophotometrically in the temperature range 321-383 K. Rate constants for the hydrogen abstraction from (TMS)(3)SiH by diarylaminyl radicals of type (4-X-C(6)H(4))(2)N* were determined by using a method in which the corresponding amines catalyze the reaction of ArO* with (TMS)(3)SiH. At 364.2 K, rate constants are in the range of 2-50 M(-)(1) s(-)(1) for X = H, CH(3), CH(3)O, and Br, whereas the corresponding value for ArO* is 3 orders of magnitude lower. A common feature of these reactions is the low preexponential factor [log(A/M(-1)s(-1)) of 4.4 and 5.2 for ArO* and Ph(2)N*, respectively], which reflects high steric demand in the transition state. A semiempirical approach based on intersecting parabolas suggests that the observed reactivity is mainly related to the enthalpy of the reaction and allowed to estimate activation energies for the reaction of (4-X-C(6)H(4))(2)N* and ArO* radicals with a variety of silicon hydrides.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP1873774	Tris(trimethylsilyl)silane		1873-77-4	Price

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