title: Conformational effects on optical rotation. 2-Substituted butanes.
abstract: The specific rotations of 2-substituted butanes (X = F, Cl, CN, and HCC) were calculated at the B3LYP/aug-cc-pVDZ level as a function of the C-C-C-C torsion angle. The results for the four compounds are remarkably similar, despite large differences in the electronic transition energies. The temperature dependence of the specific rotations for 2-methylbutyronitrile and for 2-chlorobutane was studied to give experimental information about the effect of the torsion angle on the specific rotation. The results were in good accord with B3LYP/aug-cc-pVDZ calculations. The specific rotations derived from the study of 2-chlorobutane are similar to those previously obtained for 3-chloro-1-butene, indicating that the double bond does not have a large effect on the optical rotations, but it did lead to a large difference between calculated and observed specific rotations.
authors.affiliation: Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, USA.
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Wiberg
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: Matthew R
authors.initials: MR
authors.lastname: Luderer