Apparent dipole moments and molar volumes of dimethylphenols in some nonpolar solvents

Aromatic chloroformates Ib-Ie were shown to exist in the ap conformation, in agreement with aliphatic chloroformates, i.e. the alkyl group is situated cis to the carbonyl oxygen atom as it is the case in all esters. While 4-nitrophenyl chloroformate (Ie) is in this conformation in crystal, in solution at most several tenths of percent of the sp conformation may be populated at room temperature and in nonpolar solvents only. A new analysis of dipole moments explained the previous puzzling results and demonstrated the impossibility to determine the conformation by this single method, in consequence of the strong interaction of adjoining bonds. If, however, the ap conformation is once proven, the dipole moments reveal some features of the electron distribution on the functional group, characterized by the enhanced polarity of the C-Cl bond and reduced polarity of the C=O bond. This is in agreement with the observed bond lengths and angles.

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On the distribution of potential wells and its relation to collision-induced dipole moments in nonpolar solvents. - Part I.

Journal of Molecular Liquids ◽

10.1016/0167-7322(85)80022-2 ◽

1985 ◽

Vol 31 (1) ◽

pp. 41-49 ◽

Cited By ~ 4

Author(s):

A.M. Ghoneim ◽

K.N. Abdel-Nour ◽

F.F. Hanna ◽

F. Hufnagel

Keyword(s):

Dipole Moments ◽

Potential Wells ◽

Nonpolar Solvents ◽

Induced Dipole

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The Electric Dipole Moments of Methine Dyes – Comparison of Experimental Results with Theoretical Predictions

Zeitschrift für Naturforschung A ◽

10.1515/zna-1982-0907 ◽

1982 ◽

Vol 37 (9) ◽

pp. 1024-1026

Author(s):

Z. Salamon ◽

A. Skibiński ◽

K. Celnik

Keyword(s):

Dipole Moments ◽

Stokes Shift ◽

Emission Spectra ◽

Solvent Polarity ◽

Electronic Charge ◽

Excited Singlet ◽

Nonpolar Solvents ◽

Singlet States ◽

Theoretical Predictions ◽

Excited Singlet States

Abstract Absorption and emission spectra of methine dyes in polar and nonpolar solvents were measured. From the Stokes shift as a function of solvent polarity the dipole moments of excited singlet states have been estimated and compared with the quantum chemical predictions. Also the π-electronic charge distribution in the ground and first excited singlet electronic states and bond orders of the dyes were calculated. All investigated methines showed an increase in dipole moment upon excitation to the first excited emitting state.

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The conformation of substituted hydroxyureas and hydroxythioureas in solution

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19790895 ◽

1979 ◽

Vol 44 (3) ◽

pp. 895-907 ◽

Cited By ~ 5

Author(s):

Jiří Mollin ◽

Pavel Fiedler ◽

Václav Jehlička ◽

Otto Exner

Keyword(s):

Infrared Spectroscopy ◽

Hydrogen Bonds ◽

Dipole Moments ◽

Intramolecular Hydrogen Bonds ◽

Nonpolar Solvents ◽

Steric Factors ◽

Intramolecular Hydrogen ◽

Hydroxyl Hydrogen

The conformation of 1,3-disubstituted 1-hydroxyureas Ia-d and 1-hydroxythioureas IIa-d, mostly with aromatic substituents, was investigated by means of dipole moments in dioxan solution and by infrared spectroscopy. The results are concordant for the two classes of compounds. The most populated conformation is near to the planar Z, E, ap form (A), or possibly with the hydroxyl hydrogen out of the N-C-N-O plane (between A and B). This finding from the analysis of dipole moments is corroborated by the presence of the amide-II band and absence of intramolecular hydrogen bonds. While the conformation of hydroxyureas seems to be virtually uniform, in the case of hydroxythioureas a less abundant rotamer may be present in nonpolar solvents, possibly the E, E, sp (G) or E, E, ap (F) form. The conformation found (A) is not explicable in terms of hydrogen bonds and/or steric factors when compared to symmetrically substituted ureas (thioureas) and to N-alkylhydroxamic acids.

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The Conformational Equilibrium of 1,2,3-Tribromopropane in Solution

Canadian Journal of Chemistry ◽

10.1139/v73-086 ◽

1973 ◽

Vol 51 (4) ◽

pp. 565-572 ◽

Cited By ~ 7

Author(s):

L. Ernst ◽

T. Schaefer

Keyword(s):

Conformational Equilibrium ◽

Dipole Moments ◽

Coupling Constants ◽

Spin Coupling ◽

Minor Role ◽

Nonpolar Solvents ◽

Spin Coupling Constants ◽

A Minor ◽

Spin Spin Coupling ◽

Rule Out

The p.m.r. spectra of dilute solutions of 1,2,3-tribromopropane in carbon tetrachloride, acetonitrile, and dimethylsulfoxide as well as of the neat compound are examined. From the three- and four-bond spin–spin coupling constants and from a comparison between observed and calculated dipole moments it is concluded that in nonpolar solvents the title compound exists preferably in the enantiomeric conformations a and i. In polar solvents other rotamers contribute to the equilibrium but still seem to play only a minor role. Semiempirical calculations of conformational energies rule out contributions to the conformational equilibrium from rotamers having (1:3) bromine–bromine interactions, but otherwise are only in moderate agreement with experiment.

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