REDUCED MASS CALCULATIONS, LOW-FREQUENCY VIBRATIONS, AND CONFORMATIONS OF 1,4-CYCLOHEXADIENE, 1,4-DIOXACYCLOHEXADIENE-2,5, AND 9,10-DIHYDROANTHRACENE
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Vector-based computer programs have been written in order to calculate the kinetic energy (reciprocal reduced mass) expansions as a function of the coordinate for the ring-puckering, ring-twisting (in-phase), and ring-twisting (out-of-phase) vibrations of 9,10-dihydroanthracene. The same programs also permit the kinetic energy expansions for all three vibrations to be calculated for smaller molecules including 1,4-cyclohexadiene and 1,4-dioxacyclohexadiene-2,5. The reduced mass calculated for the ring-puckering vibration of 1,4-cyclohexadiene has a minimum value for the planar conformation and increases substantially as the molecule puckers. The kinetic energy expansion for this vibration, used along with a harmonic ring-puckering potential energy function, quantitatively accounts for the observed far-infrared spectrum. This molecule is thus clearly planar. The potential energy function for 1,4-cyclohexadiene calculated from a molecular mechanics program does a remarkable job in predicting the ring-puckering frequencies when the calculated reduced mass expansion is used. The kinetic energy expansions for the puckering and twisting vibrations of 1,4-dioxacyclohexadiene-2,5 and 9,10-dihydroanthracene have also been used in conjunction with potential functions to help analyze the observed spectra for these molecules. 1988.
JOURNAL OF MOLECULAR SPECTROSCOPY
author list (cited authors)
STRUBE, M. M., & LAANE, J.
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