Raman spectra of mixtures of acetic acid with a number of carbonyl compounds have been studied. It is shown that anionoid solvents affect the molecular aggregation of acetic acid, the effect being prominent with those having strong anionoid C =O groups such as coumarin and phenyl acetate. The breakdown of the ring dimers is not, however, complete in these cases. Definite evidence has been given for the presence of open dimers. There is justification for the view that water molecules serve also as anionoid molecules in effecting the breakdown of the ring dimers of acetic acid.