Dipole moments of some substituted benzaldehydes. Conformational preference of substituents ortho to the aldehyde group

The dipole moments of a number of substituted benzaldehydes are measured in benzene solution. The angle which the dipole axis of the CHO group makes with the axis of rotation of the group is determined. The observed moments of the ortho-substituted benzaldehydes are compared with the moments calculated for free rotation as well as fors-trans ands-cis orientations of the -CHO group.o-Fluorobenzaldehyde exists mostly in thes-trans conformation.o-Chloro-,o-bromo-ando-nitro-benzaldehydcs also exist in thes-trans conformation; their observed dipole moments are even lower than the values calculated fors-trans forms, indicating mutual induction of the ortho substituents. Though 2,5-dichlorobenzaldehyde is expected to have the same dipole moment as benzaldehyde, the observed moment is significantly lower due to mutual induction of the ortho substituents. 2,5-Dimethylbcnzaldehyde has, however, almost the same moment as benzaldehyde. The dipole moment ofo-methoxybcnzaldchyde is considerably higher than the values calculated for boths-cis ands-trans conformations. An explanation is given for this.o-Hydroxybenzaldehyde exists exclusively in thes-cis form due to internal H-bonding.     

Dipole moments of some isoxazole derivatives

The dipole moments of isoxazole and 13 of its halo, amino, and nitro derivatives were measured. A method is proposed for vector calculation for estimating the direction of the dipole moment of the isoxazole ring. It is demonstrated that phenyl substituents in the 3 and 5 positions are electron donors with respect to the isoxazole ring. It was found that the dipole moments of 4-substituted 3,5-dimethylisoxazoles correlate satisfactorily with the Hammett constants.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 460–463, April, 1972.     

Dipole moments,kerr constants,and conformations of some substituted methyl cyclopropyl ketones

Conclusions The acetyl group in a substituted cyclopropane ring has an s-cis conformation that is distorted by either 15–20° (cis-2-halo-cis-3-methyl derivatives) or by 55–70° (cis-2-halo-1-methyl derivatives).Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1174–1177, May, 1977.     

1H magnetic resonance spectroscopy of some substituted acetophenones

Measurements are reported on the nuclear magnetic resonance spectra of the acetyl protons of a series of substituted acetophenones. Although the extreme values of the chemical shifts, δ for the meta- and para- substituted compounds differ only by 0·2 units, the values themselves are linearly related to the Hammett substituent constants. No such relationship exists for the ortho-substituted compounds. The magnitude of the chemical shift is independent of substrate concentration over a five-fold variation.     

Dipole moments and spatial structure of some trisarylselenomethanes

Conclusions Trisarylselenomethanes exist in a conformation with a gauche orientation of the three Ar-Se groups relative to the C-H bond of the central atom.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 436–438, February, 1977.     

Dipole moments and molecular conformations of some thioanhydrides

Electric dipole moments of methyl thiobenzoate (1.70 D), thiophthalic anhydride (3.92 D) and dibenzoyl sulphide (3.88 D) have been measured in benzene at 25° C. The predicted moments of these compounds were calculated and the results interpreted in terms of their conformations.     

Dipole moments and dielectric properties of fluorine substituted nematic liquid crystals

The effect of lateral fluorine substituents on the dielectric properties of a range of nematic liquid crystals is reported. Measurements of dipole moments and electric permittivities have been made and used to calculate Kirkwood correlation factors over a range of temperature. The results show that the extent and nature of dipole correlations are important considerations in determining the magnitude of the dielectric anisotropy in these materials. Correlation factors up to 1.4 are found, providing good evidence for the presence of parallel dipole associations.     

Mechanism of the oxidation of some substituted acetophenones byN-Bromosuccinimide in acidic media

The kinetics of the reaction of three substituted acetophenones withN-Bromosuccinimide was studied in perchloric acid media in presence of mercuric acetate. The reactions were found to be zero order with respect toNBS while the order with respect to ketones and [H⁺] was found to be unity. The addition of succinimide mercuric acetate and sodium perchlorate has no effect on the rate of oxidation and the rate increases with the decrease in dielectric constant of the medium. Kinetic investigations have revealed that the order of reactivity ism-nitroacetophenone > p-chloroacetophenone > p-methylacetophenone. TheArrhenius equation has been found to be valid in the temperature range 35–55°. Thermodynamic parameters have been calculated. Mechanistic pathways of the reactions are discussed and a rate equation is derived.Hammett's plot gives a ? value of +0.60 for methyl-aryl-ketones.     

Dipole moments and structure of the molecules of some oxazole derivatives

The values of the dipole moments of 15 substituted, 1, 3-oxazoles are given. The electron density distribution in the molecules of 2, 5-,2, 4-, and 4, 5-diphenyl-1, 3-oxazoles has been calculated by the LCAO MO method. Their heterocycle does not contain a single-electron system with the participation in conjugation of the-electrons of the C=N and C=C bonds and the p-electron pair of the oxygen. A vector calculation permits the detection of a considerable conjugation between substituents and the -electrons of the heterocycle through phenyl.