| Popis: |
The results of a combined infrared and nuclear magnetic resonance study of the meso (RS) and dl (RR) stereoisomers of 1,2,5,6-tetrachlorohexane and one meso (SRSR) form of 2,3,6,7-tetrachlorooctane are discussed with respect to the conformations of these molecules in solution, liquid and crystalline states. The predominant rotational isomer in the liquid in each case has an extended zig-zag conformation of the carbon skeletal chain; the vicinal chlorine atoms are mainly trans to each other, although other isomers occur with gauche vicinal chlorine atoms. In the crystalline phase only the extended form with trans vicinal chlorine atoms is found, except for meso -tetrachlorohexane where internal rotation of the CH 2 Cl groups leads to an extended conformation with gauche vicinal chlorine atoms. On the basis of the present results, it seems most likely that extended conformations will also be preferred in the other three stereoisomers of 2,3,6,7-tetrachlorooctane. |
