electrophile at one face of the loop formed between the alkyl chain and the aromatic ring, and departure of the leaving group (triton) from the opposite face, i.e. substitution occurs through a ‘hole’. This is the first example of electrophilic substitution at an enclosed site. The fact that steric effects in both reagent and product in hydrogen exchange are almost identical is postulated as a primary reason
已经制备了一系列的1,3-桥联的
萘,其中的烷基桥含有十个,八个或七个亚甲基,而tri位于2-或4-位。已经测量了它们在70°C的无
水三氟乙酸中的降解速率。随着桥的尺寸减小,在4-位交换的部分速率因子增加。1.28×10 7([CH 2 ] 10)2.71×10 7([CH 2 ] 8),2.97×10 7([CH 2 ] 7); cf. 1.15×10 7对于
1,3-二甲基萘,对应的σ +值为–0.812,–0.849,–0.854和–0.807。随着芳环变得更弯曲,这与增加的基态芳族性损失相一致。在2位上,部分速率因子为2.37×10 5([CH 2 ] 10),2.92×10 5([CH 2 ] 8)和1.50×10 5([CH 2 ] 7);cf.
1,3-二甲基萘为2.82×10 5,对应的σ +值为–0.614,–0.625,–0.592和–0.623。此处的结果反映了由于基态芳