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Carbon‐13 nuclear magnetic resonance spectroscopy. Substituent‐induced chemical shift effects on cyclopropyl carbons of 4‐substituted cyclopropylbenzenes
Author(s) -
Kusuyama Yoshiaki,
DyllickBrenzinger Christina,
Roberts John D.
Publication year - 1980
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270130516
Subject(s) - cyclopropane , substituent , chemical shift , chemistry , ring (chemistry) , benzene , isopropyl , carbon fibers , medicinal chemistry , photochemistry , organic chemistry , materials science , composite number , composite material
Carbon‐13 chemical shifts of the cyclopropyl carbons of eleven 4‐substituted cyclopropylbenzenes have been measured under conditions effectively corresponding to infinite dilution in DCCI 3 . The substituent‐induced chemical shifts (SCS) of both the α and β carbons of the cyclopropane ring were found to be downfield with electron‐attracting groups and upfield for electron‐donating groups. The trends for the β carbons correspond to those observed for the β carbons of 4‐substituted phenylethenes, while the trends of the α carbons are similar to those found for the α carbons of 4‐substituted isopropyl benzenes. The results for the β carbons can be rationalized by postulating a substantial contribution from a hyperconjugative resonance effect involving the σ system of the benzene ring (and its 4‐substituent) and the C‐α—Cβ bonds of the cyclopropane ring. The effects on the α carbons are in accord with a very reasonable smaller inductive polarization of the C‐αC‐β bonds than encountered for the carbons of corresponding ethenyl‐ or ethynylbenzenes.