In a recent publication [L. A. Curtiss et al., J. Chem. Phys. 106, 1063 (1997)] the enthalpies of formation of 148 molecules are calculated via the Gaussian-2 (G2) scheme, and compared to reliable experimental values. The set of molecules assembled can be used as a benchmark to test reliability of different theoretical models to predict thermochemical properties. The performance is impressive, with an average absolute deviation of only 1.58 kcal/mol. We have developed an alternative model, the J2 model which is based on the generalized valence bond-localized Moller-Plesset (GVB-LMP2) method. In this work the J2 model is tested by calculation of the enthalpies of formation of closed shell molecules containing only first row atoms from the G2 set of molecules. This is achieved by using the GVB-LMP2 method to calculate atomization energies and using experimental values to shift the energies to heats of formation. The J2 theory is shown to perform statistically better than the much more expensive G2 method. This is shown not only by a lower mean absolute deviation but even more importantly by a lower maximum deviation. The most dramatic improvement is obtained for the systems containing carbon-fluoride bonds. An explanation for this result is presented.