Phenol → 4-Hydroxybenzenesulfonic acid

Participants

Reaction Steps

440 parts of 66% oleum are added slowly at from 60° to 70° C. to 500 parts of melted phenol, and the mixture is subsequently sulfonated at 100° C. for 1 hour. The phenolsulfonic acid formed is then slowly heated at from 160° to 165° C. in a vacuum of from about 11 to 13 mm, so that only a little phenol distils off, and is maintained at this temperature until 1 g of the condensation product neutralizes 3.5 to 3.7 cm3 of 1N sodium hydroxide solution against Congo red. 90 to 100 parts of phenol are added to the condensation product thus formed, and, after the phenol has been mixed in thoroughly, the reaction mixture is again placed slowly under vacuum and heated at 165° C. in a vacuum until 1 g of the condensation product neutralizes only 2.7 to 2.5 cm3 of 1-normal sodium hydroxide solution against Congo red. 100 parts of this condensation product are melted carefully with 54 parts of 30% sodium hydroxide solution, 22 parts of 37% formaldehyde solution are added, and the mixture is then subjected to condensation at from 100° to 105° C. (about 6 hours) until a sample diluted with a little water remains clear down to a pH of 3.5 when acidified with dilute sulfuric acid.

Provenance & Evidence