PROTON AND C-13 NMR-STUDY OF PARTIALLY ORIENTED 1,4-DIOXANE - DETERMINATION OF THE R(ALPHA) STRUCTURE AND OF BOND CONTRIBUTIONS TO THE ORIENTATION

The proton and carbon-13 NMR spectra of 1,4-dioxane partially oriented in a nematic solvent were analysed, and the measured dipolar coupling constants, corrected for harmonic vibrations and for correlated defor mation, were used to obtain information about the r(alpha) structure o f the molecule. It is concluded that the 1,4-dioxane molecule oscillat es between two equivalent chair conformers, which can be described by a puckering amplitude of 0.55 angstrom. This study also indicates that each methylene group is bent away from the bisector of the ring angle towards the heteroatom. Finally, the molecular orientation of this mo lecule in N-(p-ethoxybenzylidene)-p'-n-butylaniline can be described b y three bond interaction parameters: X(cc), X(v), X(CH) (or X(CO)), co rresponding to the CC bonds, the virtual C2C6 and C3C5 bonds and the C H (or CO) bonds.