Configurational effects in 17O NMR chemical shifts of hydroxyl‐substituted, bicyclo [2.2.1]heptenes and ‐heptanes, their methylated derivatives and some related compounds

Abstract

AbstractWell resolved natural abundance 17O NMR spectra of 27 mono‐, di‐, tri‐ and tetrahydroxybicyclo[2.2.1]heptenes and ‐heptanes (norbornenes or norbornanes), their methylated derivatives and some related compounds were measured for 0.5 M or saturated solutions in acetonitrile at 65°C. In addition, the 17O NMR chemical shifts of 14 aliphatic and alicyclic alcohols were also determined for reference purposes. The 17O NMR chemical shifts of all compounds were assigned. Both methyl‐ and hydroxyl‐induced deshielding β‐effects were consistent with those reported in the literature. Similarly, observed shielding γ‐effects were in agreement with the earlier observations and characteristic especially for mutual γ‐gauche and ‐eclipsed orientations of substituents. In addition, clear shielding δ‐effects (up to 10 ppm) were observed in tri‐ or tetrahydroxynorbornanes. These δ‐effects can be related to the attractive van der Waals interactions observed earlier in 13C NMR chemical shifts.