On the Substituent-induced Chemical Shifts of the Side Chain Carbons in the para-Substituted Propylbenzenes, 2-Methylpropylbenzenes, and 2, 2-Dimethylpropylbenzenes

標記の化合物の炭素-1 3核磁気共鳴スペクトルを測定し、側鎖炭素の化学シフト(SCS)を決定した。A, Bの2-位の炭素は置換基電子効果の解釈では逆の方向性を示し、Aにおいて顕著であった。他方Cの2-位の炭素は正の方向性を示した。A, BにおけるC_2の置換基効果は2位の炭素-水素結合の分極により生じたものである。

The substituent-induced chemical shifts (SCS) for the side chain carbons in a number of the para substituted propylbenzenes (A), 2-methylpropylbenzenes (B), and 2, 2-dimethylpropylbenzenes (C) were determined. The SCS of C_2 (β-position to the ring) of A showed clearly an inverse trend in the sense of the substituent electronic effect as good as SCS (^<13>CH_3) of p-substituted ethylbenzenes. SCS (C_2) of B for electron attracting groups by resonance exhibited also an inverse trend while the magnitudes were very small. SCS (C_2) of C showed a normal trend. It was confirmed that the most important factor for the inversed SCS for SCS (C_2) for the ethylbenzenes, A, and B was the polarization of the C_2-H bond induced by the substituted phenyl moiety.