INFRARED STUDY OF BENZALDEHYDE AND 4-SUBSTITUTED BENZALDEHYDES IN CARBON-TETRACHLORIDE AND OR CHLOROFORM SOLUTIONS - ALDEHYDIC CH GROUP

The nu-CH and 2-delta-CH Fermi resonance doublet and unperturbed nu-CH and unperturbed 2-delta-CH for 4-x-benzaldehydes increase in frequency as the mole % CHCl3/CCl4 increases. One portion of the nu-CH and 2-delta-CH Fermi doublet occurs in the region 2726-2746 cm-1 and the other portion of the Fermi doublet occurs in the region 2805-2845 cm-1. The unperturbed nu-CH for 4-x-benzaldehydes is assigned in the region 2760-2810 cm-1. Submaxima are also noted for 4-x-benzaldehydes in the region 2726-2810 cm-1 and these bands are assigned to combination tones. The nu(asym).NO2 mode occurs in the region 1533.60-1538.73 cm-1 and the nu(sym).NO2 mode occurs in the region 1344.07-1345.63 cm-1 for 4-nitrobenzaldehyde in CHCl3/CCl4 solutions. The nu(sym).NO2 mode shifts to lower frequency by approximately 4.8 cm-1, while the nu(sym).NO2 mode shifts to higher frequency by approximately 1.6 cm-1 in going from CCl4 solution to CHCl3 solution. The nu-CN mode for 4-cyanobenzaldehyde increases in frequency in a nonlinear manner as the mole % CHCl3/CCl4 increases. The nu-OH mode for 4-hydroxybenzaldehyde decreases in frequency in essentially a linear manner as the mole % CHCl3/CCl4 increases. The delta-CH mode for 4-x-benzaldehydes increases in frequency as the mole % CHCl3/CCl4 increases; however, neither unperturbed nu-CH nor delta-CH correlates with Hammett sigma(p) values.