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.