Photolysis of n-pentylazomethane vapor. Reactions of the n-pentyl radical

Abstract

occur t o the 3(~,7r*) state with resulting cis-trans isomerization. It is therefore not surprising that the intersystem crossing rate constant for AIP is greater than the corresponding constants for DBO and DBH, being in excess of 1O' O sec-I.' For bicyclic azo compounds, the lower intersystem rate constants may be understood in terms of a crossing to a (n,p*) rather than a (T,T*) manifold3* and less marked differences between the equilibrium geometries of the states, resulting in less favorable Franck-Condon factors. 35 In this previous work we have used sensitization extensively as a source of triplet molecules. lr7 In Table I the interaction rate constante (kir) of a variety of substrates, including azo compounds, with several triplet (38) M. A. El-Sayed, Accounrs Chem. Res., 1, 8 (1968).Abstract: The vapor-phase photolysis of n-pentylazomethane was studied in the temperature range 24-162 ' . The product rate data fit well the proposed reaction scheme involving methyl and n-pentyl radicals. Evidence for the generation of photochemically activated n-pentyl radicals was found. The implications of this evidence to previous work on the photolysis of azoalkanes are discussed. When the concentration of photochemically activated radicals was minimized, the thermal rate constants for the isomerization andH-atom abstraction reactionsof the n-pentyl radical were determined: n-C5H11 + sec-C5H11 (17), k17 = 3.3 X lo8 exp(-l5.1 X 103/RT) sec-'; n-C5H11 + n- (20), kzo = 4.2 X 10" exp(-7.8 X lO3/RT) mol-' cm3 sec-I. The disproportionation to combination ratio at 25 O for n-pentyl radicals was estimated to be 0.14, and A(Me, n-Pe) = 0.033. C~H I~N~C H~here is almost no quantitative information in the W (10) (a) R.

Risk factors for coronary heart disease in women with systemic lupus erythematosus: The Toronto Risk Factor Study

“…The rate coefficients for the 1,4 H‐migration reactions in the 1‐pentyl radical are in excellent agreement with the experimental results of Tsang et al., Yamauchi et al., and Miyoshi et al., but only in good agreement with the results of Watkins 70–73. Similarly, the computational methods also are in excellent agreement with the 4‐methylpent‐1‐yl radical 1,4 H‐migration reaction values of McGivern et al., but they differ from the theoretical values of Bankiewicz et al 74.…”

Evaluation of density functional theory in the bond rupture of octane

“…The isomerization via 1,4-hydrogen-atom transfer is better documented in C6 and C7 alkyl radicals than for the pentyl group. 26 The C-H bond ␣ to the radical center in the pentyl radical is shorter bẙ 0.04 A than the other higher radicals and exceeds the propyl bond by 0.08 A. In short, as seen in Table I, it is more like the ethyl ␣-C-H bond.…”

The Impact of Resonance Stabilization on the Intramolecular Hydrogen‐Atom Shift Reactions of Hydrocarbon Radicals

“…These isomerization reactions play an important role in hydrocarbon combustion and pyrolysis, as they may modify the initial alkyl radical isomer population that is formed by H‐atom abstraction reactions from the parent hydrocarbon, which thereby affects both the rate and the product distribution. Due to their importance, these reactions have been the subject of many prior experimental6–15 and theoretical studies 16–21. Recently, we conducted a systematic investigation of these reactions and formulated a series of high‐pressure rate estimation rules 22.…”