title: Conformation and stereodynamics of symmetrically ortho-disubstituted aryl carbinols and aryl ethers.
abstract: By making use of low-temperature dynamic NMR spectroscopy, the rotation barriers about the sp3-sp2 bond have been determined in a number of hindered benzyl alcohols symmetrically substituted in the ortho positions, the substituents being F, Cl, Br, and Me. The free energies of activation covered the range 4.6-10.1 kcal mol-1. Ab initio computations matched satisfactorily the trend of these values and predicted the conformation adopted by these compounds. In one case, this result could be also confirmed by the X-ray diffraction structure. In the case of the corresponding methyl ethers two barriers could be measured, corresponding to the passage across two distinguishable transition states: the higher barriers covered the range 5.0-8.1 kcal mol-1 and the lower ones the range 4.7-6.2 kcal mol-1.
authors.affiliation: Department of Chemistry, University of Basilicata, Potenza, Italy.
authors.forename: Daniele
authors.initials: D
authors.lastname: Casarini
authors.forename: Lodovico
authors.initials: L
authors.lastname: Lunazzi
authors.forename: Michele
authors.initials: M
authors.lastname: Mancinelli
authors.forename: Andrea
authors.initials: A
authors.lastname: Mazzanti