Heats of formation and proton affinities by the G3 method

Proton affinities of 29 simple organic molecules calculated with the G3 method agree well with experimental results from the literature as well as with results obtained with the G2(MP2) and CBS-Q methods. The choice of empirical correction in the G3 method introduces a small systematic error on either G3 heats of formation or G3 proton affinities.