A Equilibria between Isomeric Ions Differing in the Site of Proton Attachment

A Equilibria Between Isomeric Ions Differing in the Site of Proton Attachment 

Substituents Temp. Acid system % of protonation at position Ref 

The higher thermodynamic stability of the ion with the proton at the 4-position is due to a decrease in the steric-strain on movement of one peri-CHj-group from the ring plane. 

Disagreement between kinetic and thermodynamic control has also been reported for the protonation of 1,2,3,4,6-penta- and 1,2,3.4,6,7-hexamethylnaphthaIenes.  

The possibility of formation of arenium ions in non-equilibrium ratios should be taken into ount in studying their relative stability. The proton migration between non-equivalent positions of the aromatic molecule usually occurs rather readily at —50 -i----60 °C presumably in most publications the authors dealt with equili- 

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