THE EFFECT OF para-SUBSTITUENTS ON THE CONFORMATIONAL BEHAVIOUR OF AROMATIC SIDECHAINS

Article abstract of DOI:10.1016/S0040-4020(01)87425-1

Proton nmr data are reported for some 2-aryl-1-propyl methyl esters, 2-aryl-1-propyl acetates and trifluoroacetates, 2-aryl-1-propanols and 4-aryl-2,2-dimethylpentanes.The vicinal coupling constants show that there is an increasing population of gauche Aryl/OR rotamers in the first three series (R = Me, R = COMe and R = COCF3) as electron donor groups on the aromatic ring are replaced by electron withdrawing groups.The results are ascribed to a gauche Aryl --- O interaction, the possible origins of which are discussed.