Acidität und Enolisierungstendenz

Uncatalyzed and amine catalyzed decarboxylation of acetoacetic acid: an examination in terms of No Barrier Theory

Rate constants for decarboxylation of acetoacetic acid, its anion, and its imine with aminoacetonitrile have been calculated from equilibrium constants and distortion energies using No Barrier Theory. The mechanisms of decarboxylation of both acetoacetic acid and its imine involve preequilibrium formation of the zwitterion.

Equilibria in the halogenation of some organic substances in aqueous solution

Measurements of redox potential have been used to obtain equilibrium constants for the reaction of iodine and bromine with aqueous solutions of ketones, esters and nitro-paraffins. Many of the iodination constants have an accuracy of a few per cent, but the bromination constants are not reliable to better than a power of ten. The iodination constants vary over 10 powers of ten, corresponding to considerable differences in the nature of the carbonhydrogen and carbon-iodine bonds involved. The data are used to derive the heat of the reaction R H + I-> R I + H in the gas phase, and the mean value obtained (46 kcal/mole) is consistent with earlier estimates. Approximate values are also derived for the equilibrium constants of the reaction R I->R - + I + in solution. For variations in R these are roughly parallel with the acid dissociation constants of the reaction R H->R - + H + .