Ortho-diquaternary aromatic compounds. V. Chirality and structure in hindered benzenes and napthalenes

Abstract

Ortho-disubstituted aromatics with bulky substituents are distorted so that the substituents are above and below the approximate plane of the aromatic system. This introduces chirality which was observed by proton resonance spectroscopy with and without the use of a chiral shift reagent. The more nearly planar naphthalene systems invert their chiral configurations more rapidly. Crystals of 1,2-benzenediacetic acid, α,α,α′,α′-tetramethyldimethyl ester are monoclinic, space group A2/a with a = 10.665(3), b = 8.467(2), c = 17.198(4) Å and β = 105.94(2)°. The torsion angle between the 1,2 substituents is 12.1°. Crystals of 2,3-naphthalene diacetic acid, α,α,α′,α′-tetramethyldimethyl ester are also monoclinic, space group P21/c with a = 9.0992(14), b = 18.849(3), c = 11.319(2) Å and β = 113.88(1)°. The analogous torsion angle in this case is 8.9°.