FLEXIBLE MOLECULES WITH DEFINED SHAPE .8. MODEL STUDIES AND PREDICTIONS FOR THE CONFORMATIONAL BEHAVIOR OF 2,4,6,N-POLYMETHYLATED ALKANE DERIVATIVES

Conformer equilibria of compounds having a single (6-8) or two (15-17) neighbouring dimethylpentane backbone segments have been studied. As in 2,4-dimethylpentane, a bi-conformational situation prevails in each segment. The position of the local conformer equilibria were estimate d from vicinal (3)J(H,H) coupling constants between hydrogen atoms alo ng the backbone. The position of the conformer equilibria were also ca lculated with the MM3 force field in good agreement with the experime ntal findings. A simple estimate of the position of the local conforme r equilibria based on counting the number of the low energy diamond la ttice type conformers available was used to discuss the conformer situ ation in molecules 18 and 19 possessing three adjacent dimethylpentane segments. The results were used to interprete the conformational beha viour of the more complex trimethoxyhexamethylpentadecene 2.