Semiempirical (AM1 and PM3) and ab initio Hartree-Fock and Moeller-Plesset (MP2) calculations using the 3-21G, 3-21G(d), 6-31G(d,p), 6-311G(d,p) basis sets are reported for the E and Z conformations of both the keto and iminol tautomers of formohydroxamic acid. Semiempirical and Hartree-Fock calculations are also reported for several substituted hydroxamic acids. The HF calculations tend to favor the non-hydrogen-bonding E forms, while the MP2 calculations predict both of the Z forms to be close in energy. AM1 predicts the (Z)-iminol to be the global minimum, while PM3 predicts this to be the least stable structure. The Z-keto structures are predicted to be stabilized upon substitution by methyl, cyano, and phenyl groups by all methods. The results are discussed in terms of electronic effects and known experimental results.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry