Premium
Pairwise effects of chlorine substituents on the 13 C NMR chemical shifts of dichlorobicyclo[2.2.1]heptanes (norbornanes)
Author(s) -
Laihia Katri,
Paasivirta Jaakko,
Pikkarainen Heikki,
AhoPulliainen Sirkku
Publication year - 1984
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.1270220213
Subject(s) - geminal , chemical shift , substituent , chemistry , additive function , vicinal , chlorine , stereochemistry , nmr spectra database , computational chemistry , spectral line , medicinal chemistry , organic chemistry , mathematics , mathematical analysis , physics , astronomy
The 13 C NMR spectra of nine dichlorinated bicyclo[2.2.1]heptanes (norbornanes) have been measured and assigned. The pairwise effects of chlorine substituents which cause deviations from the additivity of single‐substituent effects were investigated and are discussed. The largest effect found is the high‐field shift of carbons bearing vicinal cis substituents. In the case of geminal substitution deviations from additivity were found to be to low field and large in the γ, smaller in the β and negligible in the α chemical shifts. The observed deviations for 1,3‐disubstituted cases vary from −3.2 to +1.1 ppm at different carbons, allowing no simple explanation. Replacement of α‐hydrogen in a diaxial 1,3‐arrangement by CH 3 , OH or CI causes the single substituent effect, namely the γ a effect, to change considerably.