A-Naphthalenesulfonic acid

Problem 11.18 Account for (a) formation of the a-isomer in nitration and halogenation of naphthalene, (f>) formation of a-naphthalenesulfonic acid at 80°C and -naphthalcnesulfonic acid at 160°C. -4... 

Aerosol NS 1-Naphthalenesulfonlc acid, sodium salt EINECS 204-976-0 a-Naphthalenesulfonic acid sodium salt NSC 37036 a salt Sodium a-naphthalenesulfonate Sodium a-naphthalenesulfonic acid Sodium 1-naphthalenesulfonate Sodium naphthalene-1-sulphonate. Dispersant for pigments, extenders and fillers. Usable in aqueous media over a wide pH range. Am. Cyanamid. 

The action of steam on a-naphthalenesulfonic acid similarly yields naphthalene. Practically all aromatic sulfonic acids may be hydrolyzed with mineral acids to the parent hydrocarbons, but each sulfonic acid requires a specific minimiim temperature. a-Naphthalenesulfonic acid hydrolyzes at a much lower temperature than the beta compound. However, the beta compound with fused caustic acts quite like the corresponding benzenesulfonic acid to give /3-naphthol, sodium sulfite, and water. Under certain conditions, steam may replace the more expensive fused caustic alkalies in the hydrolysis of aromatic sulfonates that are volatile with steam ... 

Naphthalene (Table IX, p. 182). The course of the sulfonation of naphthalene is strikingly dependent upon both the reaction temperature and time at low temperatures the product is almost exclusively the -isomer (96%), at 165° the product consists of approximately 85% /5-naphthalenesulfonic acid, 15% a-naphthalenesulfonic acid, and traces of the 1,6-disulfonic acid and of /S-naphthyl sulfone (1%). The pure a-acid is isolated from the former sulfonation as follows the reaction mixture is diluted with water, filtered from unchanged naphthalene, and evaporated somewhat under vacuum at a low temperature the -acid dihydrate separates slowly, and is recrystallized from dilute hydrochloric acid (m.p. 90 ). The pure /3-acid is obtained from the high-temperature sulfonation as follows the reaction mixture is diluted with water and filtered from the sulfone, then shaken with benzene to remove the last traces of the sulfone the water layer is evaporated, and the /3-acid separates as the trihydrate on cooling to 10°. The pure trihydrate (m.p. 83 ) is obtained after several recrystallizations from 10% hydrochloric acid, in which it is practically insoluble at 10 . The trihydrate is converted into the monohydrate (m.p. 124 ) on drying in a desiccator... 

---