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

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Abstract
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.