allowance is made for the retarding effect of the five-membered ring. β-Scission of TBP alkoxyphosphoranyl radicals thus involves equatorial site selectivity. Previous results for phosphoranyl radicals (A) and (B)(X = Me3SiO) are reinterpreted in terms of equatorial site selectivity rather than the apical site selectivity originally proposed. The apicophilicity of Me3SiO is almost certainly lower than
速率常数为β-断裂环状和无环的三角双锥(
TBP)phosphoranyl基团[图形省略] P(OBU吨)X(A)和(ETO)2 P(OBU吨)X(B)[X =
环氧乙烷或(Me 3 Si)2 N]得到叔丁基自由基已经通过动力学ESR光谱法测量。
磷烷基自由基以异构体的平衡混合物形式存在,其异构体在顶端和赤道位点的占有率不同,并且相互转化的速度比进行β分裂的快得多。基团为其中访问卜吨O组对赤道部位的限制相对缓慢地进行β分裂。显示在烃溶液中在233 K下形成叔丁基自由基的β断裂的相对速率大约与其中Bu t O基团位于赤道位点的异构体的平衡摩尔分数成正比。五元环的阻滞作用。因此,
TBP烷氧基
磷烷基的β断裂涉及赤道位点选择性。
磷烷基(A)和(B)(X = Me 3 SiO)的先前结果是根据赤道位选择性而不是最初提出的顶位选择性来重新解释的。ME的apicophilicity 3的SiO被比的卜几乎肯定