Electric Dipole Moments of Several Molecules from the Stark Effect
TL;DR: 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±0,0.01 for PF3; 1.77± 0.06 for CH3CN; 3.83± 0.,3.00±0.,0.02 for HCN, 3.92± 0,2.
Abstract: 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.
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TL;DR: In this article, the microwave spectrum of n -propyl isocyanide has revealed the existence of two rotational isomers, trans and gauche, and plausible structures were fitted to the data, giving the gauche dihedral angle as 119° ± 2° from the trans position.
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TL;DR: Les moments dipolaires electriques des nitriles CH3CN, CH2ClCN and CHCl2CN, CCl3CN as discussed by the authors, CH2FCN, CHF2CN et CH2(CN)2 ont ete determines en solution dans le benzene.
Abstract: Les moments dipolaires electriques des nitriles CH3CN, CH2ClCN, CHCl2CN, CCl3CN, CH2FCN, CHF2CN et CH2(CN)2 ont ete determines en solution dans le benzene. Le moment du CF3CN a ete observe en phase gazeuse. Les spectres infrarouges de ces substances a l'etat pur ont ete determines. Des calculs vectoriels fournissent les valeurs du moment partiel du groupe CN. Il est demontre, tant par ces valeurs du moment partiel du groupe, que par l'intensite de la bande CN dans l'infrarouge, que le groupe CN subit des influences inductives tres prononces par les atomes d'halogene. D'autre part il est mis en evidence que les moments partiels des liaisons C-X (X=F,C) ne sont nullement constantes dans ces composes.
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TL;DR: The most basic compounds reported fill the current gap between the intrinsic acidity and basicity scales, which allows such basic substances to be inserted in the known acidity range for neutral compounds in order to generate the corresponding conjugate charged forms by reacting in the gas phase an appropriate acid with a neutral base.
Abstract: The currently known intrinsic basicity (DeltaG degrees ) range spans about 154 kcal/mol, from the basicity of the oxygen molecule (94.7 kcal/mol) to that of 7-isopropyl-1,5,7-triazabicyclo[4.4.0]dec-5-ene (248.4 kcal/mol). In this paper, we show that the basicities of two commercially available derivatives of ammonia, viz. F(3)N and Li(3)N, differ by 182 kcal/mol, which is greater than the above-mentioned range. We also show that the basicity range from F(3)N to Li(3)N can be spanned with simple ammonia derivatives containing single-atom substituents of electronegativity higher or lower than that of nitrogen and that basicities even higher than that of Li(3)N (a superbase) are indeed possible. The large basicity differences exhibited by these compounds are analyzed in the light of the energies of their charged and neutral forms. It should be noted that the most basic compounds reported fill the current gap between the intrinsic acidity and basicity scales, which allows such basic substances to be inserted in the known acidity range for neutral compounds in order to generate the corresponding conjugate charged forms by reacting in the gas phase an appropriate acid with a neutral base.
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TL;DR: A flexible and polarizable force field to describe acetonitrile in its three states of matter has been developed on the basis of an ab initio potential energy surface at the MP2 level as discussed by the authors.
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TL;DR: In this paper, the rotational constant and dipole moment of a Fabry-Perot absorption cell with a rotational transition of CH3CN at 36 GHz were determined.
Abstract: An absorption Stark voltmeter, using a Fabry-Perot absorption cell with a rotational transition of CH3CN at 36 GHz, has been built and evaluated. The rotational constant and dipole moment of this molecule have been redetermined and found to have the values 9198.56±0.10 GHz and 3.9185±0.0020 Debye, respectively. The short term precision of the device when used as a standard cell was better than that of the equipment which was used to test it, and was probably better than one part in 105, but there were unexplained drifts of 2 parts in 104 per day. The accuracy of the device, as a means of measuring voltage in terms of atomic and molecular constants, is 5 parts in 104. The principal errors are due to the measurement of the plate spacing (which could be reduced by using an optical interferometer to measure spacing), pulling the interferometer resonance by the external circuit, and the effects of field non-uniformities due to the coupling holes.
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TL;DR: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier.
Abstract: A microwave spectrograph is described in which the absorption of the gas being studied is modulated by the application of a periodic Stark‐effect field so that the output of the crystal detector contains a radiofrequency component which can be amplified with a narrow‐band amplifier. By using a very narrow band‐width, achieved by employing phase‐sensitive detection, high sensitivity is obtained. The klystron is swept mechanically over the frequency range. Details of the components are given.
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