Debye Units Research Articles

Microwave Spectrum, Structure, and Dipole Moment of Cyclopropene

The microwave spectra of four isotopic species of cyclopropene, CH2(CH)2, CH2CDCH, CH2(CD)2, and CDH(CH)2 were assigned and three rotational constants for each isotopic species were determined. From these data the following structural parameters were evaluated: C–C 1.515 A, C=C 1.300 A, C–H (methylene) 1.087±0.004 A, C–H (vinyl) 1.070 A, H–C–H angle 114°42′±10′ and C=C–H angle 149°55′. The uncertainties in the methylene values are the magnitude of a rotation-vibration interaction correction. The dipole moment of cyclopropene was found to be 0.455±0.01 debye unit.

The Lower Oxidation States of Gallium. III. The Constitution of Ga2Cl4 and its Analogy with Ga(AlCl4)

Dielectric constant measurements on benzene solutions of Ga/sub 2/Cl/sub 4/ give a dipole moment of 8.9 Debye units for this solute at infinite dilution. The same Raman spectrum is observed for benzene solutions of Ga/sub 2/Cl/sub 4/ and Ag(GaCl/sub 4/). These results together with molecular weight data lead to the conclusion that Ga/sub 2/Cl/sub 4/ exists in benzene as the solvated ion pairs Ga/sup +/(GaCl/sub 4/)- which aggregate with increasing concentration. Consideration of the absence of a stable gallium(I) chloride and the acid-base interaction resulting in the formation of Ga(GaCl/sub 4/) leads to the concept of stabilization of lower oxidation states toward disproportionation by strong Lewis acids and to the preparation of Ga(AlCl/sub 4/). The similarity of Ga(GaCl/sub 4/) and Ga(AlCl/sub 4/) is discussed. (auth)

Dipole Moment of Ammonia-Borane

The dipole moment of ammonia-borane, H3NBH3, has been measured as 4.9 debye units in dioxane solution; the results are discussed briefly.

The dipole moments and molecular structure of formyl and acetyl compounds

Dipole moment measurements have been made for the following formyl and acetyl derivatives, namely, formhydrazide, acethydrazide, acetaldoxime, acetoxime and formamidoxime in dioxan solution. The values obtained are 2·70, 3·15, 0·75, 0·88 and 2·24 (all in Debye units) respectively. The structure of the first four compounds have been discussed with particular reference to hyperconjugation. In the case of formamidoxime the results lead to an amidoxime structure.

Theory of the Stark Effect of the NO Molecule

Since the NO molecule has a finite electronic angular momentum $\frac{\ensuremath{\hbar}}{2}$ along the molecular axis in its ground state, the Stark effect of this molecule is very large, the molecule being effectively a symmetric top molecule rather than a diatomic molecule. The calculation is made both for weak-field and strong-field cases. An experiment by Burrus and Graybeal has been done for weak fields and gives $\ensuremath{\mu}=0.158$ Debye unit. The dielectric constant of this molecule is also discussed and it is shown that the ordinary Langevin-Debye formula can be used with the effective dipole moment ${\ensuremath{\mu}}_{\mathrm{eff}}=0.971$ \ensuremath{\mu}.

Microwave Spectrum and Structure of Sulfuryl Fluoride

The microwave spectrum of sulfuryl fluoride, SO2F2, has been reinvestigated. The spectra of the S32 and S34 species in natural abundance have been analyzed, and the structure has been determined with the aid of the S34 isotope shift. The correction for zero-point vibration was shown to be small. The structural parameters are: rSO=1.405±0.003 A, rSF=1.530±0.003 A, <OSO=123°58′±12′, and <FSF=96°7′±10′. The molecular dipole moment is 1.110±0.015 Debye units. A number of satellite lines were observed and assigned to excited vibrational states. Some anomalies in the measured rotational constants for the excited states have been interpreted in terms of a Coriolis-type interaction between the fundamentals ν4(A1) and ν5(A2). From an analysis of this interaction the frequency of the hitherto unobserved ν4(A1) fundamental was found to be 388±15 cm—1.

Microwave Stark Effect Measurement of the Dipole Moment and Polarizability of Carbonyl Sulfide

An improved microwave spectrograph has been developed which permits measurements of electric field intensity to one part in ten thousand. The instrument is employed to make precise Stark effect measurements. A method is also given for measuring the polarizability of polar molecules in a given rotational state. The transition $J=1\ensuremath{\rightarrow}2$, $\ensuremath{\Delta}M=0$ for the ground vibrational state of carbonyl sulfide (OCS) was studied and the electric dipole moment was determined to be (0.7124\ifmmode\pm\else\textpm\fi{}0.0002) Debye units. In addition the polarizability anisotropy (${\ensuremath{\alpha}}_{\mathrm{zz}}\ensuremath{-}{\ensuremath{\alpha}}_{\mathrm{xx}}$) was measured and found to be (2.4\ifmmode\pm\else\textpm\fi{}3.0)\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{3}$.Effects caused by the fourth-order term in the perturbation expansion for the Stark Effect were observed and found to be in good agreement with theoretical predictions.

Dipole Moment of the HCN Molecule

π-electronic and σ-electronic energy levels of the HCN molecule are calculated by the LCAO method with full inclusion of configuration interaction. Slater atomic orbitals with effective charge Z=3.180 for the carbon atom and 3.850 for the nitrogen atom are employed. The C–H distance is assumed to be 1.09 A and the C–N distance 1.15 A. The value 2.664 Debye units is obtained for the dipole moment of the molecule in the ground state, while the experimental value is 2.766 Debye units.

Dielectric properties of polar solutes in non-polar solvents at microwave frequencies

The dielectric loss and permittivity of solutions of polar molecules in non-polar solvents have been measured at frequencies 9.2 × 109 c/s and 3.5 × 1010 c/s. At the lower frequency independent determinations of absorption and wavelength were made on solutions of benzophenone over the temperature range 10 to 30° C. At the higher frequency the solute investigated was nitromethane and the temperature range was 10 to 40° C. Values of dipole moments obtained were 2.95 Debye units and 2.855 Debye units for benzophenone and nitromethane respectively.

Radio-Frequency Spectra ofLi6Cl by the Molecular Beam Electric Resonance Method

Transitions between the hyperfine structure levels of the rotational state of ${\mathrm{Li}}^{6}$Cl with $J=1$ were studied by the molecular beam electric resonance method. The electric quadrupole interaction constant, ${(\mathrm{eqQ})}_{\mathrm{Cl}}$, and the spin-rotation interaction constant, ${c}_{\mathrm{CI}}$, of the chlorine nucleus, and the product of the square of the molecular dipole moment, ${\ensuremath{\mu}}^{2}$, and moment of inertia, $A$, were determined in several different vibrational states. These constants, and the ratios derived from them are: The random errors in ${\ensuremath{\mu}}^{2}A$ are given in the foregoing. The systematic error was \ifmmode\pm\else\textpm\fi{}1.1\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}76}$ cgs.The vibrational constant, ${\ensuremath{\omega}}_{e}$, was found to be 536\ifmmode\pm\else\textpm\fi{}60 ${\mathrm{cm}}^{\ensuremath{-}1}$ from a study of line intensities. The magnetic field at the chlorine nucleus, ${H}_{R}$, was calculated to be 4.96\ifmmode\pm\else\textpm\fi{}0.23 gauss from ${c}_{\mathrm{Cl}}$ for ${\mathrm{Li}}^{6}$${\mathrm{Cl}}^{35}$ in the zeroth vibrational state. $\ensuremath{\mu}$, and the internuclear distance, $r$, were found from beam deflection data to be 5.9\ifmmode\pm\else\textpm\fi{}1.3 Debye units 2.4\ifmmode\pm\else\textpm\fi{}0.4 A, respectively.A static electric field was used to study the Stark effect. When the static field was weak or absent, line frequencies were found to depend on the magnitude of the radio-frequency field used to produce transitions. This effect is termed "radio-frequency Stark effect." A theory for this effect was developed and accounts for the observations.

Microwave Spectra, Dipole Moment, and Barrier to Internal Rotation of CH3NO2 and CD3NO2

The J = 1 to J = 2 and J = 2 to J = 3 transitions for CH3NO2 and CD3NO2 have been assigned for several internal rotational states. The best values of the rotational constants B and C were found to be 10 542.7 and 5876.7 Mc/sec for CH3NO2 and 8697.1 and 5254.3 Mc/sec for CD3NO2. The rotational constant for the NO2 group about the symmetry axis is 13 277.5 Mc/sec. These constants are determined assuming no inertial defect, slightly different values are calculated if other assumptions are made. Some of the assigned lines are a very sensitive function of the low barrier to internal rotation. The barrier term V6 was determined to be 6.03±0.03 calories/mole for CH3NO2 and 5.19±0.03 calories/mole for CD3NO2. The term V12 is less than 0.05 calorie/mole. The dipole moment of CH3NO2 is 3.46±0.02 Debye units.

On the Method of Atoms in Molecules III: The Ground State of Hydrogen Fluoride

Techniques suggested by the results of calculation on the hydrogen molecule are used to calculate the properties of hydrogen fluoride. The most satisfactory results are obtained using an intra-atomic correlation correction theory. This theory predicts a binding energy of 5.84 electron volts and a dipole moment of 2.33 Debye units, the experimental values of these quantities being 6.08 electron volts and 1.91 Debye units respectively.

Structure of Ozone from the Microwave Spectrum between 9000 and 45 000 Mc

Although there have been numerous investigations of the structure of ozone during the last thirty years, no studies yielded universally accepted structures until the recent infrared and microwave work. The microwave spectrum gives structural information which can be interpreted unambiguously and which is more accurate than that obtained by other methods. In this study the rotational spectra have been obtained for six isotopic ozone molecules between 9000 and 45 000 Mc. The spectra of four of them have been identified to the extent necessary to determine the spectral constants, from which moments of inertia have been calculated. By taking the moments of inertia for a molecule two at a time, structural parameters of the molecules have been calculated. Because of the inertia defect, the three different sets of parameters for each molecule have small discrepancies. There is remarkable consistency between the parameters for the different molecules. Although the resultant bond length of 1.278±0.002 A is consistent with the electron diffraction value of 1.26±0.02 A, the apex angle value of 116° 45′±30′ is inconsistent with the diffraction value of 127°±3°. The dipole moment of ozone has been determined to be 0.58±0.05 Debye unit from the Stark effects of two low J-transitions.

Microwave Absorption Spectra of MnO3F and ReO3Cl

The microwave spectra of Mn${\mathrm{O}}_{3}$F and Re${\mathrm{O}}_{3}$Cl near 1-cm wavelength have been studied. From the spectra of the first molecule and its isotopic species Mn${({\mathrm{O}}^{16})}_{2}$${\mathrm{O}}^{18}$F, the structural parameters were determined as: Mn-O=1.586 A, Mn-F=1.724 A, \ensuremath{\angle} (O, Mn, F)=108\ifmmode^\circ\else\textdegree\fi{}27\ensuremath{'}. The nuclear quadrupole coupling constant of ${\mathrm{Mn}}^{55}$ was measured as $eqQ=16.8$ Mc/sec. Because of the spin and statistics of ${\mathrm{O}}^{16}$ nuclei not all of the rotational states are allowed. It was found that, whereas in the ground vibrational states only states with $K$ a multiple of three are permissible, in the excited vibrational states of the perpendicular normal modes the states with $K\ensuremath{-}l$ a multiple of three can occur. For $K=l=\ifmmode\pm\else\textpm\fi{}1$ appreciable $l$-type doubling was observed. The amounts of $l$ doubling and their corresponding values of ${\ensuremath{\alpha}}_{v}$ were determined for Mn${\mathrm{O}}_{3}$F. The molecular dipole moment of this molecule was found to be $\ensuremath{\mu}=1.5$ Debye units. The hyperfine structure of Re${\mathrm{O}}_{3}$Cl gives for the ratio of quadrupole moments of the two abundant isotopes of Re a value of $\frac{{Q}_{{\mathrm{Re}}^{187}}}{{Q}_{{\mathrm{Re}}^{185}}}=1.067\ifmmode\pm\else\textpm\fi{}0.045$ and for the quadrupole coupling constant of ${\mathrm{Re}}^{187}$, $eqQ=253$ Mc/sec. This coupling constant and the known optical value of the quadrupole moment of ${\mathrm{Re}}^{187}$ give some information about the electronic structure of the molecular bonds, from which an approximate value of the nuclear quadrupole moment of ${\mathrm{Mn}}^{55}$ was obtained as $Q=0.55\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}24}$ ${\mathrm{cm}}^{2}$.

Microwave Spectrum and Structure of Benzonitrile

The rotational spectrum of benzonitrile has been studied in the one-centimeter region, and approximately twenty absorption lines have been fitted to the rigid asymmetric-rotor theory. The principal moments of inertia are 89.370, 326.740, and 416.183 AUA2. The evidence indicates a planar symmetric structure with ring dimensions essentially the same as in benzene. The dipole moment is 4.14±0.05 Debye units.

Stark Effect in the Microwave Spectra of KCl and NaCl

Some further lines in the microwave spectrum of KCl have been observed at frequencies predicted by the rotational constants given by recent molecular beam work. Measurements have been made on the Stark patterns of the J=2→3, v=0 line of K39Cl35 and the J=1→2, v=0 line of Na23Cl35. The dipole moments of these molecules have been determined to be 10.1±0.2 Debye units for KCl and 8.5±0.2 Debye units for NaCl. The KCl value is in fair agreement with the results of molecular beam investigations.

Microwave Spectrum of TeCS and Masses of the Stable Tellurium Isotopes

The microwave spectrum of TeCS has been examined in the rotational transitions $J=6\ensuremath{\leftarrow}5$, $J=7\ensuremath{\leftarrow}6$, and $J=8\ensuremath{\leftarrow}7$. Seven isotopes were observed and from their absorption frequencies mass ratios have been calculated. The mass values are compared with mass spectrographic data and with the recent mass surfaces of Green. The odd-even mass variation is 1.5 milli-mass-units for both ${\mathrm{Te}}^{123}$ and ${\mathrm{Te}}^{125}$. The Te-C bond distance is 1.904 A and the C-S distance 1.557 A. The molecular dipole moment was measured as 0.172\ifmmode\pm\else\textpm\fi{}0.002 Debye unit.

The Microwave Spectrum of Hydrogen Peroxide

Nine absorption lines of H2O2 and some one hundred absorption lines of D2O2 and HDO2 have been observed in the microwave frequency region using a flow system for sampling to overcome the decomposition of the peroxide at low vapor pressure. An analysis of the microwave spectrum of H2O2, using a symmetric top approximation, reveals that it is necessary to invoke hindered internal rotation to explain the experimental data. Using a sinusoidal approximation for the hindering potential yields a barrier height of about 113 cm—1. From the Stark effect calculations, a value of dipole moment of 2.26 debye units is obtained. Some limiting conditions on the values of the molecular parameters are discussed.

The Microwave Spectra, Structure, and Dipole Moment of Stable Pentaborane

The microwave spectra of several of the naturally occuring boron isotopic species of B5H9 and B5D9 have been observed. These data show that stable pentaborane consists of a tetragonal pyramid of boron atoms and has either C4 or C4v symmetry. The boron-boron distances are B1–B2=1.687±0.005 and B2–B2=1.800±0.003A. If C4v symmetry and B1–H1 and B2–H2 distances equal to 1.22A are assumed, the following boron-hydrogen parameters are obtained: B2–H3=1.35±0.02A, ∠B1–B2–H2=136°10′±30′ and ∠B1B2B2–B2B2H3=196±2°. Dipole moment values of 2.13±0.04 and 2.16±0.04 Debye units were measured for B5H9 and B5D9, respectively.

A dielectric study of a carboxymethylcellulose in aqueous solution

AbstractA carboxymethylcellulose sodium salt (CMC) with about 50% of the glucose units substituted, has been studied dielectrically by the “ellipsoid method” at various wave lengths. Aqueous solutions containing 0.1–0.0025 g./100 ml. were investigated. Dielectric increments of 2–9 dielectric constant units were obtained for these solutions. The calculated increment per gram per liter was not constant but increased considerably at the lowest concentrations, indicating the prevalence of polar molecules or aggregates at the lowest concentrations, whereas less polar aggregates dominate at higher concentrations (more than 0.01% solutions). At the lowest concentration studied, 0.0023%, the increment per gram per liter was about 120, corresponding to a molar increment of about 55,000,000. Dielectric dispersion curves were obtained which approached theoretical Debye dispersions, indicating that the CMC molecules are rather rigid. The dispersion curves were displaced toward shorter wave lengths with increasing concentration, probably due to the strong molecular interaction. At the lowest concentration a relaxation time of 4.6 × 10−7 sec. was calculated for the CMC molecule. This corresponds to a rotation of the molecules about their long axes in the electric field. An average molecular weight of about 460,000 was calculated for the CMC molecules, or polar aggregates, in very dilute aqueous solution. The electric moment of CMC was estimated to be about 1000 Debye units. In contrast to CMC, the uncharged polysaccharides dextran and ethyloxyethylcellulose did not show any deviation of the dielectric constant values from that of the pure solvent, when investigated in 0.5% aqueous solutions at various wave lengths. It was concluded that the dielectric properties of CMC are very similar to those of other polyelectrolytes studied–such as desoxyribonucleic acid, nucleohistone, and hyaluronic acid.