Steric trends and kinetic parameters for radical reductions involving alkyldiphenyltin hydrides

Abstract

Absolute rate constants and Arrhenius parameters for hydrogen atom abstraction by primary alkyl radicals from methyldiphenyl-, ethyldiphenyl-, butyldiphenyl-, isopropyldiphenyl-, cyclohexyldiphenyl-and (trimethylsilyl)methyldiphenyltin hydride were determined in tert-butylbenzene through utilization of the '5-hexenyl radical clock' reaction. At 80°C, rate constants (k H ) for all hydrides were found to lie in the range (8.2-11.5) Â 10

(o‐Phenylenediamino)borylstannanes: Efficient Reagents for Borylation of Various Alkyl Radical Precursors

“…We performed radical clock experiments [46][47][48] to evaluatet he reactionr ate for the S H 2s tep. 6-Bromo-1-hexene 2u was reacted with an excess amount of borylstannane 1 (Figure 3).…”

“…These rate constantsf or the borylation of 5hexen-1-yl radical B were found to be slightly larger than that for the reduction with Bu 3 SnH (1.1 10 6 /M•s at 80 8C). [48] In addition, the radical clock experiment wasp erformed at different reactiont emperatures and an Eyring plot gave the activation parameters: DH°(2.68 kcal mol À1 ), DS°(22.0 cal mol À1 •K), and the activation energy DG°(9.23 kcal mol À1 )( Figure S4). The experimental value of DG°almost matched the calculations (11.4 kcal mol À1 in Figure2B).…”

Synthesis, characterization and enantioselective free radical reductions of (1R,2S,5R)-menthyldiphenylgermane and its enantiomer

“…24 Provided that the ÔclockÕ rate constant (k c ) is well established for any given temperature, then the rate equation (Scheme 3) will provide a value for the hydrogen transfer rate constant (k H ). It should be noted that several published Arrhenius parameters exist for the ring-closure of the 5-hexenyl radical.…”

“…24 In addition to this, we also chose to examine the reaction of tributylgermane, a reagent that has been studied previously, albeit not in tert-butylbenzene. We expected our data for Bu 3 GeH to correlate with those reported previously, providing a further test for our methodology.…”

26 Mechanisms of reactions in solution

“…À have been measured 353 in near-and super-critical water 354 Subtle steric effects determine 355 the reactivity order as R varies for H abstraction from SnRPh 2 H. Hydrogen-atom abstraction from SnR 3 H by an arylperoxy radical is faster for R Bu t than for SiMe 3 . 356 Mechanistic studies of peroxonitrite N(O)OO À , 357^366 trioxodinitrate, 367,368 NO 369 and inorganic oxidants generally 370 continue to receive attention because of their relevance to cellular processes 371 À and H respectively, and for homolysis of N(O)OO À .…”