Influence of the Molecular Environment on the Carbonyl Frequency. Electronic Calculation

The KvC=O force constants of formaldehyde, acetaldehyde, acetone, glyoxal, p-benzoquinone, o-benzoquinone, and of chloroacetaldehyde have been determined by Pariser-Parr-Pople's SCF-MO procedure. The theoretical expression for the force constant corresponding to this theory is given. The KvC=O force constant is found to decrease in the order formaldehyde, chloroacetaldehyde, acetaldehyde, acetone; this is due to the corresponding decrease of the effective electronegativity of the carbonyl carbon atom. The KvC=O force constant decreases also in the series acetone, o-benzoquinone, p-benzoquinone, and in the series acetaldehyde, glyoxal; this is due to conjugation effects. The force constants calculated by this theory agree satisfactorily with the experimental values.