Knowledge Bank

The vibrational spectra of acetamide and thioacetamide have been recorded. The $1300-1400cm-1$ regions of both the compounds exhibit Fermi resonances. The equations for Fermi polyad have been set up to obtain anumber of anharmonic coupling constants from the observed frequencies and their intensity ratios. These constants have been used to obtain a set of anharmonicity constants. The IR spectrum of acetamide exhibits a few hot bands tentatively arising from intermolecular hydrogen bonding N-H... O.A potential function is presented for this bond which can yield the intermolecular force constant.