If s-naphthylamine and 0-naphthol be reduced, tetrahydro products are obtained in which the aminoor oxy-bearing half of the molecule becomes aliphatic in character.
If a-naphthylamine and a-naphthol be reduced, the hydrogen atoms attach themselves to the non-substituted half of the molecule, and the compounds so obtained resemble aminodiethylbenzene, C 6 H 3 NH 2 (C 2 H 5) 21 and oxydiethylbenzene, C 6 H 3.
A-Naphthylamine is prepared by reducing a-nitronaphthalene with iron and hydrochloric acid at about 70° C., the reaction mixture being neutralized with milk of lime, and the naphthylamine steam-distilled.
Sodium in boiling amyl alcohol reduces it to aromatic tetrahydro-a-naphthylamine, a substance having the properties of an aromatic amine, for it can be diazotized and does not possess an ammoniacal smell.
The a-naphthylamine sulphonic acids are used for the preparation of azo dyes, these dyes possessing the important property of dyeing unmordanted cotton.
The most important is naphthionic acid, I-amino-4sulphonic acid, produced by heating a-naphthylamine and sulphuric acid to 170-180° C. with about 3% of crystallized oxalic acid.
0-Naphthylamine is prepared by heating 13-naphthol with zinc chloride-ammonia to 200-210° (V.
Numerous sulphonic acids derived from 0-naphthylamine are known, the more important of which are the 2.8 or Badische, the 2.5 or Dahl, the 2.7 or S, and the 2.6 or Bronner acid.
(3-Nitronaphthalene is prepared by acting with ethyl nitrite on an alcoholic solution of 2-nitro-a-naphthylamine in the presence of sulphuric acid (E.
A-Naphthol may be prepared by fusing sodium-a-naphthalene sulphonate with caustic soda; by heating a-naphthylamine sulphate with water to 200° C. (English Patent 14301 (1892)); and by heating phenyl isocrotonic acid (R.
4), formed when diazotized naphthionic acid (a-naphthylamine-4-sulphonic acid) is boiled with dilute sulphuric acid (Nevile and Winther, Ber., 1880, 1 3, p. 1 949), or when sodium naphthionate is heated with concentrated caustic soda solution under pressure at 240°-260° C. (German patent 46307 (1888)).