title: meso-Tetrahydropyranylperoxides: molecular structures in solution, in the crystal, and by DFT calculations and their isomerization to the racemate.
abstract: The crystalline peroxide 3a is the main product (out of 10 theoretically possible) from the aerial peroxidation of all-cis-2,4,6-trimethyltetrahydropyran (2a). It has a similar structure both in solution and in the crystal as shown by nuclear Overhauser effects and X-ray analysis, respectively. Theoretical calculations at a density functional theory level (B3LYP/6-31G) provide insight into the stabilities of the different stereoisomers of this peroxide, accounting for the facile, acid-catalyzed isomerization from the meso form to the racemate. Peroxide 3b, which is the 2-tert-butyl analogue of 3a, out of 22 theoretically possible isomers, crystallizes in a similar meso form. As a result of crystal packing effects and the intrinsically (axial) chiral peroxy "chromophore" that deviates slightly from the antiperiplanar conformation, both enantiomorphic forms of 3b are encountered in the lattice.
authors.affiliation: Forschungszentrum Karlsruhe, Institute for Nanotechnology, Postfach 3640, D-76201 Karlsruhe, Germany. silviu.balaban@int.fzk.de
authors.forename: Teodor Silviu
authors.initials: TS
authors.lastname: Balaban
authors.forename: Andreas
authors.initials: A
authors.lastname: Eichhöfer
authors.forename: Ion
authors.initials: I
authors.lastname: Ghiviriga
authors.forename: Holger
authors.initials: H
authors.lastname: Hugo
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wenzel