EPR分析表明,在[6]环戊烯中,同位素同位素对同位素异构体之间电子转移的平衡常数的影响要大得多(即C 6 H 6 -。 + 13 C 6 D 6 = C 6 H 6 + 13 C 6 D 6- 。)比[8]环戊烯体系(即C 8 H 8 -。 + 13 C 8 D 8 = C 8 H 8 + 13 C 8 D 8- )高。)。这是由于芳香性的影响。
EPR分析表明,在[6]环戊烯中,同位素同位素对同位素异构体之间电子转移的平衡常数的影响要大得多(即C 6 H 6 -。 + 13 C 6 D 6 = C 6 H 6 + 13 C 6 D 6- 。)比[8]环戊烯体系(即C 8 H 8 -。 + 13 C 8 D 8 = C 8 H 8 + 13 C 8 D 8- )高。)。这是由于芳香性的影响。
Contrasting free energies of electron transfer from [6]- and [8]annulenes to their perdeuteriated and per-13C analogs
作者:Cheryl D. Stevenson、Steven J. Peters、Kerry A. Reidy、Richard C. Reiter
DOI:10.1021/jo00032a049
日期:1992.3.1
A very large equilibrium isotope effect (confirmed via physical separation of the isotopes involved) was observed via the EPR analysis of a mixture of benzene and perdeuteriated-per-C-13-benzene competing for a deficient number of electrons in tetrahydrofuran (THF) in the presence of 18-crown-6 (18C6). The K(eq) for the reaction C6H6.-,K+(18C6) + (C6D6)-C-13 = C6H6 + (C6D6)-C-13.-,K+(18C6) is 0.096 +/- 0.008 at -100-degrees-C. An analogous competition for electrons exists between [8]annulene and perdeuteriated-per-C-13-[8]annulene. In contrast to the benzene system the K(eq) for the reaction C8H8.-,Na+ + (C8D8)-C-13 = C8H8 + (C8D8)-C-13.-,Na+ in liquid ammonia is 1.20 +/- 0.04 at -100-degrees-C. Similar contrasting results (but smaller in magnitude) were observed for the benzene and cyclooctatetraene perdeuteriated and per-C-13 systems. The results are interpreted in terms of the divergence of the [6]annulene system from aromatic character upon electron addition and the convergence of the [8]annulene system toward aromatic character upon electron addition.
Contrasting free energies of electron transfer from [6] and [8]annulenes to their erdeuteriated-per-13C analogues
作者:Gerald R Stevenson、Steven J Peters、Kerry A Reidy
DOI:10.1016/s0040-4039(00)97011-4
日期:1990.1
EPR analysis shows that the equilibrium isotopeeffectupon the equilibrium constant for electrontransferbetweenisotopicisomers is much larger in [6]annulene (i.e. C6H6−. + 13C6D6 = C6H6 + 13C6D6−.) than in the [8]annulene systems (i.e. C8H8−. + 13C8D8 = C8H8 + 13C8D8−.). This is due to the effects of aromaticity.
EPR分析表明,在[6]环戊烯中,同位素同位素对同位素异构体之间电子转移的平衡常数的影响要大得多(即C 6 H 6 -。 + 13 C 6 D 6 = C 6 H 6 + 13 C 6 D 6- 。)比[8]环戊烯体系(即C 8 H 8 -。 + 13 C 8 D 8 = C 8 H 8 + 13 C 8 D 8- )高。)。这是由于芳香性的影响。