An Investigation on the Vibrational Frequency of C=O Bond in Benzoic Acid / 第三军医大学学报

The infrared spectra of benzoic acid in its solid form and in various solvents were determined.The result confirmed that the carbonyl bond of the dimer form of benzoic acid occurs at 1694 cm~(-l),but not at 1653 cm~(-1).The influences of hydrogen bond (polar solvent) and solvent effect (nonpolar solvent) on the vibrational frequency of C=O bond was also studied.In the nonpolar solvent,owing to the increment of the dielectric constant (?) of the solvent,C=O stretching frequency decreases slightly and the relationship between them can be expressed with the following formula:Here K and C are two contants,V_v and V_s represent the vibrational frequencyof C=O bond of benzoic acid in vapor and in solvent respectively.