C6H5-CH2-CH2-CH2-CH3；C6H5-CH(CH3)-CH2-CH3；C6H5-C(CH3)3四个同分异构体.
符合条件2的共有9种[（邻、间、对）甲基正丙基苯；（邻、间、对）甲基异丙基苯；（邻、间、对）乙基乙基苯]