Structure of an Ultraviolet Absorber: 2-(3'-t-Butyl-2'-hydroxy-5'-methylphenyl)-benzotriazole

Abstract

The 5′-methyl derivative (1) of 2-(2′-hydroxyphenyl) benzotriazole is an effective ultraviolet absorber, the planar molecule having a strong intramolecular (OH…N) hydrogen bond which is considered responsible for its high photostability. X-Ray analysis of the title compound (2) has shown that the introduction of a bulky t-butyl substituent ortho to the phenolic hydroxyl group results in a stronger intramolecular interaction; the OH…N spacing of 2.568(4) Å is shorter than that [2.616(2) Å previously reported for compound (1).