Spectroscopic Studies of the Hydrogen Bond I. A Photometric Investigation of the Association Equilibrium in the Vapor of Acetic Acid

Abstract

The association equilibrium in the vapor of acetic acid has been studied by photometric measurement of the intensity of a narrow O[Single Bond]H band at lambda9750 which appears to be characteristic of the single molecules. The results are in reasonable agreement with vapor density measurements, indicating that the association is at least largely due to hydrogen bond formation and that two hydrogen bonds are formed in the majority of the double molecules. An O[Single Bond]H absorption characteristic of the double molecules could not be observed in the vapor state, due to insufficient path length, but in the liquid and in carbon tetrachloride solutions a broad band was found with maximum around lambda10,100. It is suggested that the spectroscopic criterion for the presence of hydrogen bonds is not the disappearance but rather the shift and modification of the O[Single Bond]H absorption.