Kinetics of reversible recombination of aromatic C-centered radicals
The kinetics of the reversible recombination of the 2‐phenyl‐ (I), 2‐p‐methoxyphenyl‐(II), and 2‐p‐nitrophenyl‐3‐oxo‐2,3‐dihydrobenzothiophene‐2‐yl (III) radicals have been investigated. Recombination rate constants of R(I–III) have been determined in different solvents (2k1 ∼ 109 M−1 s−1). The rate...
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Veröffentlicht in: | International journal of chemical kinetics 1985-07, Vol.17 (7), p.735-747 |
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Sprache: | eng |
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Zusammenfassung: | The kinetics of the reversible recombination of the 2‐phenyl‐ (I), 2‐p‐methoxyphenyl‐(II), and 2‐p‐nitrophenyl‐3‐oxo‐2,3‐dihydrobenzothiophene‐2‐yl (III) radicals
have been investigated. Recombination rate constants of R(I–III) have been determined in different solvents (2k1 ∼ 109 M−1 s−1). The rate of reaction (I) with R(I–III) decreases with increasing solvent viscosity η. In the toluene‐vaseline oil mixture (2 ≲ η ≲ 120 cP) the recombination of R(I–III) is molecular mobility limited. The thermodynamic parameters of reaction (I) have been determined: ΔH0 = 20–30 kcal/mol. Activation volumes ΔV 1≠ for recombination of R(II) have been measured. In n‐propanol ΔV 1≠ is equal to the viscous flow activation volume of the solvent ΔV d≠. In toluene and chloroform ΔV 1≠ < ΔV d≠. For the last two solvents the activation volumes of the cage reaction have been estimated ΔV 1≠(r) = −(2–3) cm3/mol. Visible‐range absorption spectra and ESR spectra have been recorded for R(I–III). The role of cage effect in the reactivity anisotropy averaging of R(I–III) is discussed. The potential of the high‐pressure tests for deriving information about the elementary act of a fast bimolecular reaction is considered. |
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ISSN: | 0538-8066 1097-4601 |
DOI: | 10.1002/kin.550170704 |