The spin delocalization substituent parameter σ(?)——6.The spin-delocalizing abilities of the thiomethyl,cyclopropyl and t-butyl groups.Synthesis of three substituted trifluorostyrenes  

作　　者：JIANG,Xi-Kui JI,Guo-Zhen SHI,Yi-Qun Shanghai Institute of Organic Chemistry,Academia Sinica,Shanghai 200032 

出　　处：《Chinese Journal of Chemistry》1991年第2期162-166,共0页中国化学（英文版）

基　　金：This work was financially supported by the National Natural Science Foundation of China.

摘　　要：Three substituted α,β,β-trifluorostyrenes(TFS's),i.e.,p-thiomethyltrifluorostyrene(4), p-cyclopropyltrifluorostyrene(5)and p-t-butyltrifluorostyrene(6),have been synthesized.The rate constants(k_2)of the thermal cyclodimerization of these compounds have been measured in the tem- perature range 120—160℃.The polar parameters σ_(mb) of these TFS's calculated from ^(19)F NMR chemi- cal shifts are:for p-thiomethyl,-0.18;p-cyclopropyl,-0.31 and p-t-butyl,-0.22.The spin delo- calization substituent parameters σ'_T(140°)of p-thiomethyl,cyclopropyl and t-butyl groups are 0.59, 0.27 and 0.30 respectively.Thus all of these groups act as electron-donating groups which can also effectively stabilize a spin.Three substituted α,β,β-trifluorostyrenes(TFS's),i.e.,p-thiomethyltrifluorostyrene(4), p-cyclopropyltrifluorostyrene(5)and p-t-butyltrifluorostyrene(6),have been synthesized.The rate constants(k_2)of the thermal cyclodimerization of these compounds have been measured in the tem- perature range 120—160℃.The polar parameters σ_(mb) of these TFS's calculated from ^(19)F NMR chemi- cal shifts are:for p-thiomethyl,-0.18;p-cyclopropyl,-0.31 and p-t-butyl,-0.22.The spin delo- calization substituent parameters σ'_T(140°)of p-thiomethyl,cyclopropyl and t-butyl groups are 0.59, 0.27 and 0.30 respectively.Thus all of these groups act as electron-donating groups which can also effectively stabilize a spin.

关 键 词：TFS The spin delocalization substituent parameter The spin-delocalizing abilities of the thiomethyl cyclopropyl and t-butyl groups.Synthesis of three substituted trifluorostyrenes 

分 类 号：O6[理学—化学]