The Friedel-​Crafts acetylation of naphthalene. Evidence for concurrent second- and third-​order reactions

The Friedel–Crafts acetylation of naphthalene has been shown to give varying α : β isomer ratios as a function of concentration of the reactants. In consequence the ratio is strongly time- and temperature-dependent. Values of the α : β ratio (determined by an extrapolation procedure, for 1,2-dichloroethane solution) for the limit of zero reaction time, were plotted against reactant concentration, to give a straight line having a near-zero intercept. From this it is inferred that, whereas β-acetylation is essentially first-order with respect to the acylating reagent, α-acetylation is dominantly second-order in acylating reagent.