EFFECT OF SOLVENT ON THE ANHARMONICITY AND SHAPE OF THE $\equiv$C-H STRETCHING MODE OF 1-HEPTYNE
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Date
1972
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Publisher
Ohio State University
Abstract
The frequency, band half-width, peak height absorption coefficient, and integrated absorption coefficient of the 1-0, 2-0, 3-0 transitions (3400--3300, 6600--6500, 9700--9500 $cm^{-1}$) for the -C-H stretching mode of 1-heptyne have been measured near $25^{\circ} C$ in the vapor phase and in solution in the following fifteen solvents: n-heptane, $CCl_{4}, CH_{2}Cl_{2}$, cyclohexane, isooctane, benzene, $CH_{2}ClCH_{2}Cl, CS_{2}, toluene, C_{2}Cl_{4}, CH_{3}NO_{2}, CH_{3}I, CHBr_{3}, C_{4}Cl_{6}, CHCl_{3}$. The changes in frequency shift from the vapor to solution and band half-width with vibrational quantum number were compared with predictions of solvent effect theories. The integrated absorption coefficient increased on going from the vapor phase to solution for the 1-0 and 3-0 transitions for the solvents studied while the opposite effect occurred for the 2-0 transition. Dipole correlation functions, correlation times, and second, third, and fourth truncated band moments were computed for the 1-0 and 2-0 transitions. It was found that very accurate frequency measurements would be required to evaluate solvent effects on anharmonicity constants. Correlations of the measured spectral properties with each other were investigated. In general the solvents studied could be divided into the following groups on the basis of their effect on most spectral properties: (1) saturated hydrocarbons, (2) completely halogenated hydrocarbons and $CS_{2}$, (3) aromatic hydrocarbons, and (4) partially halogenated hydrocarbons and $CH_{3}NO_{2}$.
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Author Institution: Department of Chemistry, Kansas State University