Detection of Non-Conjugative Interactions in Rigid Cyclic Molecules by Using Carbon-13 N.M.R. Shift Values

Abstract

In previous work, interaction between formally unconjugated unsaturated groups was detected by comparing the ¹³C n.m.r. shift values of the sp² atoms of difunctional compounds with those of the corresponding monofunctional compounds. This procedure has now been used to investigate possible interactive effects in a range of rigid alicyclic systems where steric and conformational factors cannot be involved, namely, the 2,6-disubstituted adamantane (6), 4,8-disubstituted 2-thiaadamantane (7), 2,6-disubstituted noradamantane (8), and 2,5-disubstituted norbornane (9) systems. In each case interaction was detected between the unsaturated groups of the non-conjugated dimethylene, methylene ketone, and diketone derivatives of these ring systems. The nature of this effect is under further investigation.