Reliable reaction enthalpies for neutral amide hydrolysis and the heat of formation for formamide

High level ab initio electronic structure calculations have been done for the hydrolysis reaction X(2)NC(O)Y + H2O --> X(2)NH + HOC(O)Y for X = Y = H (formamide) and for X = H and Y = CH3 (acetamide). Calculations are reported with a variety of basis sets and a variety of correlation levels based on molecular orbital (MO) theory as well as with a variety of density functional theory (DFT) gradient-corrected (nonlocal) functionals, The convergence of the hydrolysis energies with respect to the computational method is discussed. The highest level calculations yield 0.3 +/- 0.4 and 0.1 +/- 0.4 kcal/mol at the MO and DFT levels, respectively, for X = H and Y = CH3 as compared to an experimental value of 0.4 +/- 0.9 kcal/mol. For X = Y = H, the hydrolysis energies are 1.7 +/- 0.4 (MO) and 2.2 +/- 0.4 (DFT) kcal/mol. The heat of formation of formamide was calculated from the isodesmic reaction H2NC(O)CH3 + HOC(O)H --> H2NC(O)H + HOC(O)CH3, giving Delta H degrees(f) = -45.6 +/- 1.1 (MO) and -46.2 +/- 1.1 (DFT) kcal/mol. These values for Delta H degrees(f) (formamide) yield 1.9 +/- 1.3 (MO) and 2.5 +/- 1.3 (DFT) kcal/mol for the hydrolysis reaction.