| abstract |
1,209,919. 4-Hydroxybenzotriazoles. GEIGY (U.K.) Ltd. 22 July, 1968 [21 July, 1967], No. 33536/67: Heading C2C. [Also in Divisions C4, C5 and C7] The invention comprises compounds of the formula wherein R represents a C 1-4 alkyl group, and a general process for the preparation of such compounds and of 4-hydroxybenzotriazole wherein a benzotriazole of the formula where X represents hydrogen or a C 1-4 alkyl group, is sulphonated using oleum, or a mixture of oleum and cone. H 2 SO 4 , and the resulting 4- sulphonic acid is hydrolysed to the required compound by fusing with an alkali metal hydroxide. The sulphonation step is preferably effected using excess oleum at 80-200‹ C. in the presence of mercuric oxide as catalyst. The hydrolysis step may be effected using an excess of alkali, preferably NaOH or KOH, at 220- 300‹ C. Examples describe the preparation of 4-hydroxybenzotriazole, the 5-methyl and 5- butyl derivatives thereof and the corresponding 5-sulphonic acids. The benzotriazoles are metal deactivators and may be used as corrosion or tarnish inhibitors for metals or to stabilize materials susceptible to deterioration in contact with metals (see Divisions C4, C5 and C7). |