The application of the Urey-Bradley force field to the in-plane vibrations of benzene
01 Jan 1961-Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (Elsevier)-Vol. 17, Iss: 7, pp 719-730
TL;DR: In this article, a Urey-Bradley force field reproduces the ingold assignment of the planar B2u vibration fundamentals of benzene but does not give acceptable agreement with the M air -H ornig assignment.
About: This article is published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy.The article was published on 1961-01-01. It has received 128 citations till now.
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TL;DR: In this article, the quadratic and most important cubic force constants of benzene have been determined from ab initio Hartree-Fock calculations with a double-zeta basis set.
Abstract: The quadratic and the most important cubic force constants of benzene have been determined from ab initio Hartree–Fock calculations with a double‐zeta basis set. Some constants have also been recalculated using other basis sets, including a polarized one. A few empirical scale factors, applied to the ab initio force field, allow the reproduction of a large number of observed vibrational frequencies, isotope shifts, and Coriolis constants within the uncertainties of experiment and the harmonic model. It is shown that the simultaneous utilization of ab initio and spectroscopical information is sufficient for the conclusive resolution of the uncertainties and alternatives in previous empirical force fields. The resulting scale factors can be used directly to obtain force fields for other aromatic hydrocarbons from ab initio calculations. Reproduction of the observed infrared intensities is only moderately successful, even with the polarized basis set. The calculated vibronic coupling constants show qualitative agreement but important deviations from previous simpler calculations. The predicted vibrational patterns confirm Lindholm’s assignment of the photoelectron spectrum of benzene.
412 citations
01 Jan 1982
345 citations
TL;DR: The vibrational spectrum of the pyridinium ion, C5H5NH+, and the N-deuterated species has been studied in several pyrinium salts as discussed by the authors.
Abstract: The vibrational spectrum of the pyridinium ion, C5H5NH+, and the N-deuterated species has been studied in several pyridinium salts. By comparison with benzene and deuterobenzene (with which the pyr...
243 citations
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TL;DR: An algorithm for the systematic calculation of Urey-Bradley force constants has been programed for a digital computer (the Datatron 204) as mentioned in this paper, where the potential energy being transformed from Urey•Bradley space to internal coordinate space by a matrix Z. This same matrix is also used to transform the Jacobian of λ with respect to the force constants from internal coordinate to Urey • Bradley space.
Abstract: An algorithm for the systematic calculation of Urey‐Bradley force constants has been programed for a digital computer (the Datatron 204). The secular equation is set up and solved in internal coordinates, the potential energy being transformed from Urey‐Bradley space to internal‐coordinate space by a matrix Z. This same matrix is also used to transform the Jacobian of λ with respect to the force constants from internal‐coordinate to Urey‐Bradley space, thereby allowing the direct determination of Urey‐Bradley force constants. A method is described whereby the Z matrix and Wilson's G matrix may be set up by the computer from the geometrical parameters of the molecule.
188 citations
TL;DR: In this paper, the infra-red spectrum of crystalline benzene has been studied at −12°C, −65°C and −170°C as well as the liquid at 28°C.
Abstract: The infra‐red spectrum of crystalline benzene has been studied at −12°C, −65°C and −170°C as well as the liquid at 28°C. The lines are extremely sharp, the mean line width for fundamentals being 7 cm−1 in the crystal. In three cases, it is less than the spectral slit width. All out‐of‐plane degenerate modes are split by about 10 cm−1. Selection rules are obeyed and agree with the reported x‐ray structure. All ungerade fundamentals are observed directly, some for the first time. Fifty‐two combination bands are observed. The frequency assignments of Ingold et al. are confirmed except for the B2u species. Evidence is cited for re‐assigning ν14 from 1648 cm−1 to 1310 cm−1 and ν15 from 1110 cm−1 to 1150 cm−1. Ingold's isotopic data does not conflict with this change. Combination frequencies involving torsional lattice modes are apparently observed at −170°C.
181 citations
TL;DR: The pure rotational Raman spectra of benzene and benzene-d6 at a pressure of ǫ atm were photographed in the second order of a 21ft. grating.
Abstract: The pure rotational Raman spectra of benzene and benzene–d6 at a pressure of atm. were photographed in the second order of a 21 ft. grating. Both spectra were resolved and analyzed, yielding for the rotational constants the values B0(C6H6) = 0.18960 ± 0.00005 cm.−1, B0(C6D6) = 0.15681 ± 0.00008 cm.−1and, therefore, for the moments of inertia about an axis perpendicular to the figure axisIf it is assumed that the benzene molecule has the planar hexagonal structure, the moments of inertia just given yield for the internuclear distances in benzene the values
153 citations
TL;DR: In this article, a normal co-ordinate treatment of benzene is carried out using the Urey-Bradley force field, and also a slight modification of it, which favors the assignment of v 14 to 1618 cm −1, close to the original suggestion of I ngold, and in the absence of definitive experimental evidence this assignment is adopted.
70 citations
TL;DR: In this article, a least square method was used to calculate the force constants for bromide and vinylidene fluoride using complete deuterium isotopic data and a Urey-Bradley potential function.
Abstract: Force constants have been calculated by a least‐squares method for vinylidene bromide and vinylidene fluoride using complete deuterium isotopic data and a Urey‐Bradley potential function. The results of this work show that the ``C=C stretching'' and ``CH2 scissors'' modes are not pure vibrations but exhibit appreciable coupling between C=C stretching and CH2 bending coordinates. Further, the molecules within the vinylidene‐halide series do not seem to have constant normal coordinates and hence the frequency differences are not entirely associated with changes in the force field. It follows that in molecules of this type, it is dangerous to infer changes in bond strength from observed frequency shifts except with the aid of a complete normal‐coordinate analysis.
58 citations