Acidities of 4‐substituted benzoic, bicyclo[2.2.2]oct‐1‐yl and bicyclo[2.2.2]oct‐2‐enyl carboxylic acids

Experimental gas‐phase acidities are reported for a series of 4‐substituted bicyclo [2.2.2] oct‐1‐yl carboxylic acids and for a limited number of the corresponding bicyclo [2.2.2] oct‐2‐enyl carboxylic acids. Similar acidities are also reported for additional 4‐substituted benzoic acids, allowing a comparison of field and resonance effects between the three series. Ab initio molecular orbital calculations for these series of acids confirm the conclusion that the aromatic acids display direct field and resonance effects, whereas the acidities in the aliphatic series acids are largely determined by direct field effects.