A dipole moment study of organo-chalcogen compoun

Long-range coupling constants for α-13C nuclei in phenyl-X-R (X = O,S,Se,Te) derivatives. Internal rotational information

“…Photoelectron spectra (28) and electric dipole moments (29) are in apparent agreement with such a conclusion, although it has been stated (30) that 'H and 13C nmr spectra of C6H5XR (X = 0, S, Se, Te) in CCl, solution do not contradict the hypothesis of planar conformations. The p.. .T conjugation in methyl phenyl telluride is even weaker than for the selenium compound (29) and photoelectron spectra are consistent (31) with a 0 of at least 60°, implying that the perpendicular is possibly more stable than the planar conformer. ' This paper reports on another approach to the estimation of the internal rotational potentials about the C,?-X bonds in some phenyl-X-R derivatives.…”

A physical Study on the Aromaticity of 4H-Pyran-4-one, 9H-Xanthen-9-one, and related sulphur Compounds

“…1 and 2 for atom numbering), it can be safely inferred that q3 (in 3-a and 3'-a) is inferior to q3 (in 2-a and 2'-a) and q3 (in 3-b and 3'-b) is smaller than q3 (in 2-b and 2'-b) (cf. [18]): <?3 (in 3-a) = 0.0388 e as against q3 (in 2-a) 0.0724 e, from [35]. Note also that in (III'), and in (II'), one benzene sextet disappears.…”

“…The techniques used to determine the dielectric permittivity, specific volume and refraction index of the solutions (and solvent) are described elsewhere [18,19], For each solute, wmax (here reported to only three decimal places although it is known to five or six decimal places), a0, ß (in cm3g-1), P2oc and RD (both in cm 3 mol-1), and p in Debye units (1 D = 3.3356 x IO-30 C m) are given in Table 1. Table 2 lists the dipole moments of the com pounds here studied, as well as those of other deri vatives calculated by additivity or measured in ben zene solution.…”

An esr and CIDEP study of the photoreduction of chromone and chromanone and their organometallic radical adducts

“…In nature benzopyran analogs are widespread and many of them have interesting biological and physical properties (1,2). As a class of compounds, chromones and chromanones have been attracting much attention among chemists in different fields.…”

“…The initial polarization of the chromone triplet via the differential intersystem crossing processes to the T,, sublevel is typical of many of the aromatic carbonyl compounds (14,15). In order to preserve the spin polarization in the primary chemical processes [2], the reaction with phenol must proceed at a rate comparable to or greater than the relaxation process which can destroy the triplet spin polarization. Although phenol is a good hydrogen donor, the abstraction reaction [2] will only proceed efficiently if the triplet state is of T(rzn*) character (1 1).…”