The proton magnetic resonance spectra of some disubstituted acetophenones

An accurate measurement of the chemical shifts and the coupling constants of some disubstituted acetophenones has been made. The acetophenones studied contained nitro, bromo or amino groups substituted in either the 3,4 or 2,5 positions. For compounds with no substituent adjacent to the acetyl group, the chemical shifts and the coupling constants estimated by the simple additivity of the substituent increments were found to be in reasonable agreement with the experimental values. The two nitro, bromo derivatives substituted in positions 2 and 5 probably prefer the conformer in which the proton H‐6 is adjacent to the acetyl methyl group whilst the 3,4‐disubstituted bromo, nitro and bromo, amino derivatives prefer the conformer in which the H‐6 proton is adjacent to the carbonyl group.