Protonation of a β-diketone; an intramolecular hydrogen bond with an extremely deshielded proton
Abstract
Studies of the protonation of 1,3-diphenyl-2-methylpropane-1,3-dione in HBr/CF2Br2 show that the proton is held between the oxo groups in an unusual hydrogen bond, giving rise to a 1H n.m.r. signal at δ 21.44 with a negative Δδ(H,D) value.