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Reactions of pyrene (Ï ) and perylene (Pe) with dimeric dicarbanions of α-methylstyrene (<sup>â </sup>αα<sup>â </sup>) were investigated in tetrahydrofuran at 25°C. The reaction of pyrene proceeds according to the following mechanism: [graphic omitted] followed by fast reaction of [graphic omitted] with <sup>â </sup>α. or Ï . The following values were obtained: K Ï = 120 M, k 1= 1.3.10<sup>â 2</sup> sec<sup>â 1</sup>, k 2 K 1â ¼1.5 à 10<sup>â 5</sup> M sec<sup>â 1</sup>, and k 2/k â 1= 8.5 à 10<sup>â 2</sup> M.The direct endothermic electron-transfer <sup>â </sup>αα<sup>â </sup>+Ï â <sup>â </sup>αα. +Ï <sup>â </sup>. (1â ²) is much slower than the formation of the adduct <sup>â </sup>Î±Î±Ï <sup>â </sup>. Its decomposition supplies <sup>â </sup>αα. more rapidly than reaction (1â ²). The exothermic electron-transfer [graphic omitted] is probably faster than the addition [graphic omitted]. Thus, the kinetics of the stationary state provides k 2/k â 1=(k â 1+kâ ²â 1) and k 2 K 1(K 1=k 1/(k â 1+kâ ²â 1).The reaction of perylene is too fast to be followed by our techniques, but electron-transfer from <sup>â </sup>αα<sup>â </sup> to [graphic omitted] was investigated. The following mechanism was established: [graphic omitted] The product k 2[graphic omitted] is 6.5 à 10<sup>â 2</sup> sec<sup>â 1</sup>. |
