Dipole moments of methylgermanium fluorides

Successive halogen substitution in methylgermanium fluorides and chlorides leads to different observed trends in the dipole moments of the various compounds. These trends may be explained in terms of hybridisation and polarisability effects. If π bonding exists it is small in the fluorine compounds but possibly somewhat larger in the chlorine compounds.     

Dipole moments of organophosphorus compounds

Russian Chemical Bulletin -     

Dipole moments of sterically hindered p-hydroxystyrylpyridines

On the basis of measurements of dipole moments and a comparison of the results obtained with those calculated by a vectorial additive scheme, the structure of a series of sterically hindered p-hydroxystyrylpyridines have been determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1528–1531, November, 1973.     

Dipole moments of symmetrical molecular systems

It is shown that quantization of nuclear motion causes the intrinsic dipole moment of a molecular system to depart from the classical representation, e.g., it is different from zero for symmetrical molecules. A formula is derived for the mean dipole moment ¯p as a function of temperature with allowance for the internal motion of the nuclei, which is functionally related to the dipole moment. Calculations are performed for ammonia with allowance for the inversion splitting, which is due to tunneling between two equivalent equilibrium configurations having their dipole moments in opposite directions. The temperature coefficient of ¯p may be positive or negative, in accordance with the relation between the tunneling frequency and the temperature; the formula usually employed is valid only in the limiting case of low frequencies and high temperatures. A deduction is given for the criterion for instability of the maximally symmetrical configuration with respect to odd nuclear displacements (dipole distortions); this is based on a simple model system having an inversion center, a totally symmetric ground state, and a triply degenerate odd excited state of the T_1u type. The experimental consequences of the results are discussed, as well as the concept of symmetry for a molecular system in which the maximally symmetrical configuration is unstable.