Polar Substituent Effects in the Solvolysis of Acyclic Tertiary Chlorides Polar Effects VI

The influence of twenty substituents R on the solvolysis rates and products of tertiary chlorides R - CH₂CH₂C(CH₃)₂Cl (7) has been studied. H, CH₃, (CH₃)₂NCH₂, ClCH₂, Cl, CN and NO₂ exert an inductive effect only, as the good correlation of the rates with the corresponding inductive substituent constants σ shows. Bulkier alkyl groups, i.e. isopropyl and t-butyl, lower the rate due to a Baker-Nathan effect, while the n-electron donors CH₃S, CH₃O, HO and (CH₃)₂N and the σ-electron donors (CH₃)₃Sn and HOCH₂ cause rate increases based on σ constants. These accelerations are attributed to C,C-hyperconjugative and inductomeric effects which arise in the transition state for ionization. A comparison of the reactivity of the acyclic chlorides 7 and the corresponding 1-R-substituted 3-bromoadamantanes 1a shows that polar substituent effects are more strongly transmitted in the rigid bicyclic compounds 1a than in the flexible acyclic compounds 7.