Search

Abinitio MP2/aug-cc-pvDZ and density functional B3LYP calculationswith the 6-311(d,p) basis set are performed to investigate theconformation of desflurane (CHF2OCHFCF3), itsacidity/basicity and its interaction with one water molecule. Thecalculations include the optimized geometries, the harmonic frequenciesof relevant vibrational modes, the binding energies with water, anda detailed natural bond orbital (NBO) analysis Iincluding the NBOcharges, the hybridization of the C atoms and the intra- and intermolecularhyperconjugations. The relative energies of the two most stable conformersare discussed as a function of the total hyperconjugative energiesresulting from the interaction of lone pairs of the O and F atomsto the different antibonding orbitals of desflurane. The proton affinityis the same for both conformers but the acidity of the CH bond islarger for the less stable conformer. The binding energies of thecomplexes of two desflurane conformers with one water molecule rangefrom −2.75 to −3.23 kcal mol–1. Dependingon the structure of the complexes, the CH bonds involved in the interactionare contracted or elongated. The σ*(CH) occupation predominatesover the hybridization effect in determining the CH bond length. Thereis an unexpected charge transfer to the external OH bond of the watermolecule. This effect is in good agreement with theoretical data onthe complexes between fluorinated dimethyl ethers and water and seemsto depend on the number of F atoms implanted on the ethermolecule. [ABSTRACT FROM AUTHOR]