The filtrate, on standing, deposited another 4.5 g of product which was added to the above first crop. Solids were apparent within a few min. The stirred reaction mixture was heated at reflux for 8 h. After cooling to room temperature, the solids were removed by filtration and washed lightly with CH2Cl2. This was heated on the steam bath for an hour, added to 1 L H2O, and acidified with HCl, producing a heavy crystalline mass.
Hexane is also an excellent recrystallization solvent.
As an alternate method, the oxidation of the naphthaldehyde to the naphthol can be achieved through heating the aldehyde in acetic acid solution containing hydrogen peroxide. The mixture was held at reflux on the steam bath for 2 h, cooled, and quenched in 1 L H2O. Trial extraction evaluations have shown that the starting phenol, as well as the product ether, are extractable into CH2Cl2 from aqueous base. This was finely ground under an equal weight of hexane, and the residual crystalline solids removed by filtration. These proved to be quite rich in the desired ether. The fractions containing the desired ether were pooled, the solvent removed under vacuum and the residue, which weighed 3.86 g, was dissolved in 1.0 mL hexane and cooled with dry ice.