Duca José S., Gallego Mariana H., Pierini Adriana B., Rossi Roberto A.
INFIQC, Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, 5000 Córdoba, Argentina.
J Org Chem. 1999 Apr 16;64(8):2626-2629. doi: 10.1021/jo980657r.
The nucleophilic substitution reaction of the chlorides RMe(2)CCH(2)Cl (R = Me, 4; Ph, 5a; PhCH(2), 5b) and their relative reactivities toward diphenyl phosphide ions were studied under irradiation in liquid ammonia. The relative reactivities determined were k(5a)()/k(4)() congruent with 9 and k(5b)()/k(4)() congruent with 0.85. These reactions are proposed to occur through the S(RN)1 mechanism. The higher reactivity of 5a is explained on the basis of its higher electron affinity due to the phenyl substitution and the efficient intramolecular electron transfer from this group to the C-Cl sigma bond (intra-ET catalysis). Although 5b also has a phenyl ring, its lower reactivity is ascribed to a decrease in the rate of the intra-ET by elongation of the bridge in one methylene unit. The relative reactivity of 5a versus 5b (k(5a)()/k(5b)() congruent with 6.4) is proposed to indicate the ratio of the intra-ET rates of the radical anions of both compounds. AM1 calculations performed on the system are in agreement with the experimental results.
研究了氯化物RMe(2)CCH(2)Cl（R = 甲基，4；苯基，5a；苯甲基，5b）的亲核取代反应及其在液氨中光照下对二苯基磷离子的相对反应活性。测定的相对反应活性为k(5a)()/k(4)()约等于9，k(5b)()/k(4)()约等于0.85。这些反应被认为是通过S(RN)1机理发生的。5a的较高反应活性是基于苯基取代导致的较高电子亲和性以及该基团向C-Cl σ键的有效分子内电子转移（分子内电子转移催化）来解释的。尽管5b也有一个苯环，但其较低的反应活性归因于通过在一个亚甲基单元中延长桥链而导致的分子内电子转移速率降低。5a与5b的相对反应活性（k(5a)()/k(5b)()约等于6.4）被认为表明了两种化合物的自由基阴离子的分子内电子转移速率之比。对该体系进行的AM1计算与实验结果一致。
