Abstract
Chemical shift data for the formyl proton in some 30 aromatic aldehydes are reported. It was found that meta- and para-substituted benzaldehydes exhibited this peak in the range 9.65–10.20 δ, while ortho-substituted compounds appear at lower field, 10.20–10.50 δ; the former shifts show an approximate correlation with the Hammett sigma parameter. Evidence for steric inhibition of resonance is presented for some ortho-substituted compounds and some interesting solvent effects are discussed.