Dielectric Studies. VIII. Dipole Moments of Solvents in Nonpolar Solvents of Unknown Molecular Weights1

1947 ◽  
Vol 69 (10) ◽  
pp. 2558-2559 ◽  
Author(s):  
Norman C. C. Li ◽  
C. V. An ◽  
W. H. Wu
Keyword(s):  
Dipole Moments ◽  
Dielectric Studies ◽  
Nonpolar Solvents

Conformation and electronic structure of aromatic chloroformates

1987 ◽  
Vol 52 (4) ◽  
pp. 970-979 ◽  
Author(s):  
Otto Exner ◽  
Pavel Fiedler
Keyword(s):  
Electronic Structure ◽  
Oxygen Atom ◽  
Strong Interaction ◽  
Electron Distribution ◽  
Room Temperature ◽  
Functional Group ◽  
Dipole Moments ◽  
Carbonyl Oxygen ◽  
Nonpolar Solvents ◽  
Single Method

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.

Dielectric Studies of Aggregation Phenomena with Separated α and β Chains of Human Hemoglobin

1971 ◽  
Vol 26 (5) ◽  
pp. 453-457 ◽  
Author(s):  
Peter Schlecht
Keyword(s):  
Concentration Dependence ◽  
Dipole Moments ◽  
Dielectric Dispersion ◽  
Human Hemoglobin ◽  
Dielectric Studies ◽  
Dielectric Measurements ◽  
Aggregation Phenomena

The concentration dependence of the dielectric dispersion between 100 kHz and 15 MHz has been investigated for separated α and β chains of human hemoglobin. It is shown that such dielectric measurements can give very detailed information on aggregation phenomena. Specific dielectric increments and dipole moments of monomeric and aggregated chains could be obtained.

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

1986 ◽  
Vol 90 (10) ◽  
pp. 2244-2247 ◽  
Author(s):  
A. Codoner ◽  
I. Monzo ◽  
F. Tomas ◽  
R. Valero
Keyword(s):  
Dipole Moments ◽  
Molar Volumes ◽  
Nonpolar Solvents

Dielectric studies. Part XXIII. Relaxation data and apparent dipole moments of aniline and some disubstituted aromatic amines

1969 ◽  
Vol 47 (4) ◽  
pp. 681-686 ◽  
Author(s):  
S. W. Tucker ◽  
S. Walker
Keyword(s):  
Aromatic Amines ◽  
Dipole Moments ◽  
Frequency Dispersion ◽  
Dielectric Studies ◽  
Relaxation Data ◽  
Time Model ◽  
Electric Dipole Moments ◽  
Microwave Frequencies ◽  
Dielectric Absorption ◽  
Dielectric Results

Dielectric studies have been carried out at microwave frequencies on dilute solutions of aniline, p-chloro-, p-bromo-, and m-chloro-anilines, and o-, m-, and p-toluidines at 25 °C in cyclohexane and p-xylene. The static dielectric constant has also been measured at 2 MHz. In addition o- and m-toluidines have been measured at 50 °C and p-toluidine at 15, 35, and 50 °C.The dielectric results, particularly those at 70.01 GHz, establish that there is more than one relaxation process present and the data have been analyzed on a two relaxation time model, the longer of which τ1, is identified as molecular relaxation. The cause of the lower electric dipole moments found from this method as opposed to the non-dielectric absorption methods is discussed. It follows that there is either an additional higher frequency dispersion or (and) a high atomic polarization for aniline and o-, m-, and p-toluidines. Work at still higher frequencies is required to study this further and to establish more precise values of τ2.

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

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.

The conformation of substituted hydroxyureas and hydroxythioureas in solution

1979 ◽  
Vol 44 (3) ◽  
pp. 895-907 ◽  
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.

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

1973 ◽  
Vol 51 (4) ◽  
pp. 565-572 ◽  
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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