Debye Units Research Articles

Electric Dipole Moments of Several Molecules from the Stark Effect

The following molecular electric dipole moments, in Debye units, have been obtained from the Stark effect of pure rotational spectra observed in the microwave region: 0.234±0.004 for NF3; 1.03±0.01 for PF3; 1.77±0.02 for POF3; 3.00±0.02 for HCN; 3.92±0.06 for CH3CN; 3.83±0.06 for CH3NC; 1.79±0.02 for CH3F; 0.75±0.01 for CH3CCH; 1.26±0.01 for SiF3H. All values apply to the ground vibrational state.

Dielectric Constant Measurements of Chlorine Trifluoride at 9400 mc/sec

The dielectric constant of chlorine trifluoride was determined at 9400 mc/sec by measuring the change in the resonant frequency of a cavity when it is filled with the vapor. Corrections were made for the amount of dimer formed. The monomer molar polarization was best represented by P=15.944+1882.0/T°K cc and the dipole moment was 0.554 Debye unit. The average dimer molar polarization was found to be 49.8 cc assuming no dipole moment.

The Microwave Spectrum of a Slightly Aspherical Top—The Structure and Dipole Moment of Sulfuryl Fluoride

The microwave spectrum of the slightly aspherical rotor, sulfuryl fluoride, has been investigated. Seven lines were found in the twenty to thirty thousand megacycle region. Six of these lines were assigned to J=1→2 and 2→3 rotational transitions of the molecule S32O2F2 and the other to the 111→212 transition of S34O2F2. These lines can be fitted to within the limits of experimental error (0.002 percent) with the following reciprocal moments of inertia: a32=5139.77 mc a34=5139.77 mcb32=5077.81 mc b34=5073.00 mcc32=5057.22 mc c34=5052.51 mc Structural parameters were determined from these moments and the assumption of C2v symmetry. The latter was confirmed by intensity measurements. S–O 1.370±0.01A S–F 1.570±0.01A O–S–O angle 129∘38′±30′ F–S–F angle 92∘47′±30′The S–O distance differs by −0.06A from the published electron diffraction value. Measurements on stark lobes of the three 1→2 transitions of S32O2F2 gave a quantitative check of the assignment and a value of 0.228 Debye units for the dipole moment.

The Microwave Spectrum of Methyl Stannane

The microwave spectrum of methyl stannane between 25,500 and 29,000 mc is reported. All of the observed lines may be assigned to the J=1→2 rotational transitions of the isotopic species representing the five most abundant tin isotopes. The dipole moment was found from the Stark splitting to be 0.68±0.03 Debye unit. Insufficient information is available for a complete structure determination, but if tetrahedral angles and a C–H distance of 1.090A are assumed, the data can be fitted with a C–Sn distance of 2.143±0.002A and a Sn–H distance of 1.700±0.015A. The influence of hindered internal rotation on the spectrum is discussed.

The Structure of Trifluoromethyl Acetylene from the Microwave Spectrum and Electron Diffraction Pattern

Measurements, in the microwave region, of the J = 3→4 rotational transitions of trifluoromethyl acetylene and several of its isotopic modifications have been made, and the moments of inertia, IB (in a.m.u.-Å2), have been found for the ground vibrational state: for CF3CCH, 175.613, CF3C13CH, 177.024, CF3CC13H, 181.302, and for CF3CCD, 187.462. Three lines corresponding to J = 3→4 transitions of CF3CCH in the excited vibrational state v10 = 1, and two lines corresponding to v10 = 2 and v10 = 3, have also been measured and interpreted according to Nielson's theory of l-type doubling in symmetric tops. From Stark effect measurements at different electric field strengths the dipole moment of CF3CCH in the ground vibrational state has been found to be 2.36±0.04 Debye units. For the ground vibrational state the microwave data lead to the following bond distances: C–H, 1.056±0.005Å; C≡C, 1.201±0.002A. The C–C and C–F distances were calculated from the measured moments of inertia for several assumed values of the FCF angle. Electron diffraction experiments were also made, and the intensity curves calculated for the assumed microwave models were compared with the observed visual curve. From the combination of microwave and electron diffraction results the best agreement was obtained with the following set of parameters: ∠FCF, 107.5°±1°; C–C, 1.464±0.02A; C–F, 1.335±0.01A.

Molecular Dipole Moments and Stark Effects. II. Stark Effects in OCS

The dipole moments of OCS for several isotopic species and vibrational states have been determined from the Stark splitting of the $J=1\ensuremath{\rightarrow}2$ rotational transition. The value of the ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{32}$ moment is 0.7085\ifmmode\pm\else\textpm\fi{}0.004 debye units. The ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{34}$ and ${\mathrm{O}}^{16}$${\mathrm{C}}^{13}$${\mathrm{S}}^{32}$ moments differ from this by less than 0.2 percent. The ${\mathrm{O}}^{16}$${\mathrm{C}}^{12}$${\mathrm{S}}^{32}$ molecule in the excited bending mode (${v}_{2}=1$) is treated formally as a slightly asymmetric top which produces a doublet. Measurement of Stark effect for these lines gives a dipole moment of 0.700\ifmmode\pm\else\textpm\fi{}0.004 debye. Upon introduction of a Stark voltage, two weak lines appear on either side of the doublet ${v}_{2}=1$. They are explained as transitions involving the doublet levels which are forbidden in zero field, but allowed upon the introduction of a perturbing field.

Dipole Moment and Structure of Morpholine

WE have determined the dipole moment of morpholine* in benzene solution at 20° and have obtained a value of 1·48 (Debye units are used throughout). The result is of interest as the structure of morpholine (II) can be compared with those of dioxan (I) and piperazine (III).

A study of the properties of hydrogen films on tungsten by the method of contact potentials

In a study of the properties of hydrogen on tungsten by the method of contact potentials the following points have been established:(1) The contact potential of a 92% covered surface of hydrogen on tungsten against bare tungsten is 1·04 V., and the Richardson constants for such a surface are, approximately,A = 30, b = 5·60 V.(2) A film of deuterium is 20 m V. positive relative to a similar hydrogen film.(3) Over the range of temperatures and pressures used by Bryce in a study of the production of atomic hydrogen the films are nearly saturated, so that the production of atomic hydrogen is primarily due to a molecule striking a bare tungsten atom, one atom being adsorbed and the other going into the gas phase.(4)The condensation coefficient for hydrogen molecules on cold tungsten is 0·01.(5) The effective dipole moment of each hydrogen atom on the surface is −0·42 Debye unit and is independent of the fraction of the surface covered.

The Emission of Visible Light from Cavitated Liquids

Emission of visible light from a number (14) of pure liquids and from some aqueous and nonaqueous solutions occurs during cavitation by intense sound waves of 8900 c.p.s. The intensity of the visible components of the radiation varies directly with the numerical product of viscosity (in poise) and dipole moment (in Debye units) and inversely with the temperature. In the case of polar solutes in nonpolar solvents the intensity varies with the concentration of the dipole. The light originates in cavitated areas or at the surface of the cavities, and is therefore proportional to the amount of cavitation, and in consequence, to the acoustic power input.

Structure of the Nitro Group

THE usual formula given to the nitro group is containing a co-ordinate link1, and it is sup-ported by the parachor evidence2. On account of this dissymmetry, both the compounds 1-4-dinitrobenzene and 1-3-5-trinitrobenzene should possess finite electric dipole moments. Also studies in benzene3 and in naphthalene4 have resulted in moments of 0·6 and 0·8 Debye units being ascribed to the di- and tri-substituted compounds respectively.