The torsional barrier in aromatic carbonyl compounds. V. Carbon-13 DNMR study of stable protonated p-substituted acetophenones

✍ Scribed by Jean-François Barthelemy; Roland Jost; Jean Sommer

• Book ID: 102951671
• Publisher: John Wiley and Sons
• Year: 1978
• Tongue: English
• Weight: 519 KB
• Volume: 11
• Category: Article
• ISSN: 0749-1581
• DOI: 10.1002/mrc.1270110904

✦ Synopsis

Abstract

The barrier to internal rotation around the phenyl–carbonyl bond in a series of stable protonated p‐substituted acetophenones has been determined by means of low temperature ^13^C NMR and total bandshape analysis resulting in a value of Δ__G__ = 48.1 kJ mol^−1^ for the unsubstituted protonated compound. The energy results and the ^13^C chemical shifts are in good agreement with the quasi‐planarity of the ground state in p‐substituted protonated acetophenones. The barrier heights are discussed in terms of contributions from steric and resonance effects.