To determine the enthalpy of formation, a series of accurate calculations are carried out using the W1 method. This method is another composite quantum chemistry method used to compute the thermodynamics in this paper. This method includes valence electron correlation at the level of CCSD and CCSD(T) calculations, inner core electron correlation at the levels of CCSD(T) using the Dunning basis set, scalar relativistic correction as well as spin-orbit coupling. Overall more correlation energy is captured in this method when compared to the CCSD method using an aug-cc-pVTZ (augmented correlation-consistent valence triple-ζ ) atomic orbital basis set. It has a mean absolute error of approximately 0.3 kcal/mol and unlike other methods includes only a single, molecule-independent empirical parameter. It has been developed for molecules composed of atoms from the first two rows of the periodic table which encompasses the molecules being studies in this work.