title: Ab initio calculation of torsion and inversion barriers of the amino group in aminopyrimidines.
abstract: Calculations of the barriers to internal rotation and inversion of the amino group in substituted pyrimidines have been performed. Torsion and inversion barriers were determined by several ab initio methods: HF, HF/MP2, MP4, CISD, QCISD, QCISD(T), CCSD, and CCSD(T). DFT method also employed. Dependencies of the calculated barrier heights on the basis set and the electron correlation level and on the substitution position of the nitrogen atom in the ring were studied. We have determined that for certain molecules relatively low level calculations may eventually provide adequate results, but in general, higher level calculations are necessary.
authors.affiliation: Laboratory of Structure and Quantum Mechanics of Molecules, Chemistry Department, Moscow State University, Vorobyevy Gory, Russia.
authors.forename: Anna Yu
authors.initials: AY
authors.lastname: Golovacheva
authors.forename: Alexey N
authors.initials: AN
authors.lastname: Romanov
authors.forename: Vladimir B
authors.initials: VB
authors.lastname: Sulimov
mesh_terms: D000588:Amines / Q000737:chemistry*; D008958:Models, Molecular; D011743:Pyrimidines / Q000737:chemistry*
chemical_list: D000588:Amines; D011743:Pyrimidines