Knowledge Bank

The effect of hydrogen bonding on the near ultraviolet absorption band of $\alpha -$ or $\beta -$naphthol has been studied. Triethylamine, ether and nitromethane have been used as the proton acceptor. Experimental results show that proton accepting ability increases in the order of triethylamine $>$ ether $>$ nitromethane and that the red shift of absorption maximum caused by the hydrogen bonding increases in the order of $\alpha$-naphthol $>$ phenol $>$ $\alpha$-naphthol. On the basis of these results, the mechanism of hydrogen bonding and of the red shift will be discussed.