G. Cevasco, F. Sancassan, S. Thea
Dec 12, 2002
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Journal
Arkivoc
Abstract
Temperature-dependent 1 H- NMR experiments on the cyclic tetramers 1a, 1b, and 1c, obtained through reaction of the appropriate 3,5-disubstituted 4-hydroxybenzenesulfonyl chlorides and aliphatic tertiary amines in aprotic solvents, indicate that these cyclic compounds retain conformational flexibility. Free energies for the intra-annular rotation of the substituted benzene rings have been determined from the rate constants at the coalescence temperature. The influence of the nature of the ring substituents on the conformational barrier has been evaluated.