GAS-PHASE ACIDITY OF SOME CARBOXYLIC ACIDS CALCULATED BY MNDO

Gas-phase acidities of 15 aliphatic carboxylic acids, X CH -,COOH, have been calculated using the MNDO method. Among the substituted groups exist the electron donor alkyl groups and electron acceptor halogens. The average error in acidity is within the experimental uncertainty of the data. Systematic errors have been found for the substituents which form internal hydrogen bondings. A reasonable correlation does exist between the gas-phase acidity and the net atomic charges on the acidic hydrogens in the neutral form and the net atomic charges and ionization potentials of the anions. There is no correlation between the gas-phase acidity and HOMO and bandgaps