title: Effect of substituents and conformations on the optical rotations of cyclic oxides and related compounds. relationship between the anomeric effect and optical rotation.
abstract: The effect of substituents on the specific rotation of substituted cyclic oxides (X = F, Cl, CN, and HCC) and related compounds was studied via geometry optimization at the B3LYP/6-311+G** level followed by calculations of the specific rotation with B3LYP/aug-cc-pVDZ and, when practical, also with B3LYP/aug-cc-pVTZ. In some cases chiral samples were prepared so that the calculated specific rotations could be compared with experimental data. With most compounds there was only a minor effect of the basis set on the specific rotations. With the oxiranes and oxetanes, the chloro derivative gave a different behavior than the other substituents, but all substituents behaved in the same fashion with trans-2-methyl-1-X-cyclopropanes. Therefore the unusual behavior of chlorooxirane probably results from an interaction between oxygen and chlorine rather than being due to the presence of a three-membered ring. Chlorine is also an unusual substituent for the tetrahydrofurans. The effect of conformation on the calculated specific rotations was examined with the axial and equatorial 2-substituted tetrahydropyrans, where the anomeric effect is operative with the axial substituent, and also the 3-substituted tetrahydropyrans that would not be subject to the anomeric effect. The unusual effect of chlorine was seen only when it is antiperiplanar with respect to the oxygen.
authors.affiliation: Department of Chemistry, Yale University, New Haven, CT 06520-8107, USA. kenneth.wiberg@yale.edu
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Wiberg
authors.forename: Shaun M
authors.initials: SM
authors.lastname: Wilson
authors.forename: Yi-gui
authors.initials: YG
authors.lastname: Wang
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Vaccaro
authors.forename: James R
authors.initials: JR
authors.lastname: Cheeseman
authors.forename: Mark R
authors.initials: MR
authors.lastname: Luderer
mesh_terms: D002244:Carbon / Q000737:chemistry; D002625:Chemistry, Organic / Q000379:methods*; D002713:Chlorine / Q000737:chemistry; D003521:Cyclopropanes / Q000737:chemistry; D005027:Ethylene Oxide / Q000031:analogs & derivatives / Q000737:chemistry; D005663:Furans / Q000737:chemistry; D008956:Models, Chemical; D015233:Models, Statistical; D008962:Models, Theoretical; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry
chemical_list: D003521:Cyclopropanes; D005663:Furans; D010087:Oxides; D002713:Chlorine; D002244:Carbon; C015061:chloroethylene oxide; D005027:Ethylene Oxide; D009584:Nitrogen; D010100:Oxygen