to the extended aromatic pi system. The electronic effect of the distal methyl group and the steric hindrance of the coplanar phenyl ring combine to promote bromide attack at the beta carbon. Attack on this pi bond is insensitive to the electronic effect of meta and para substituents on the ring but is very (sterically) sensitive toward all ortho substituents.
在弱酸性溶液中,将HBr添加到1-苯基丙-1-炔中主要产生抗马尔科夫尼科夫产物。在本文中,我们考虑了对此行为的五种可能解释,并得出结论,一致的加成发生在与扩展的芳香族pi系统正交的
乙炔pi键上。远端甲基的电子效应和共平面苯环的位阻共同促进了
溴化物对β碳的攻击。对该π键的攻击对环上的间位和对位取代基的电子效应不敏感,但对所有邻位取代基非常(空间)敏感。