A study of thermodynamic acidities of enols with the semiempirical computational method AM1

Using the semiempirical computational method AM1 we have computed the enthalpies of ionization of enols 1–21 and correlated these values with solution and estimated pK a 's. From this initial study it appears that, in general, it is possible to predict the pK's of acyclic enols within ± 1 pK a unit. On the basis of this correlation we predict the pK a 's of 1-hydroxy-1,3-butadiene (3-butenal enol) (9.7) and 1,1-difluoroacetone enol (9.6) and …