Naphthalene - Encyclopedia

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'NAPHTHALENE, C 1 oH 8, a hydrocarbon discovered in the "carbolic" and "heavy oil" fractions of the coal-tar distillate '(see Coal-Tar) in 1819 by A. Garden. It is a product of the action of heat on many organic compounds, being formed when the vapours of ether, camphor, acetic acid, ethylene, acetylene, &c., are passed through a red-hot tube (M. Berthelot, Jahresb., 1851), or when petroleum is led through a red-hot tube packed with charcoal (A. Letny, Ber., 1878, II, p. 1210). It may be synthesized 1py passing the vapour of phenyl butylene bromide over heated soda lime (B. Aronheim, Ann., 1874, 171, p. 219); and by the action of ortho-xylylene bromide on sodium ethane tetracarboxylic ester, the resulting tetra-hydronaphthalene tetracarboxylic ester being hydrolysed and heated, when it yields hydronaphthalene dicarboxylic acid, the silver salt of which decomposes on distillation into naphthalene and other products (A. v. Baeyer and W. H. Perkin, junr., Ber., 1884, 1 7, p. 451): - C6H4 < CH2Br + NaC(C02R)2 - 7Cs H4 C CH2C(C02R)2 CH 2 Br NaC(C02R)2 CH2C(C02R)2 C 10 1-1 8 E - CeH9?CH2 CH C02H Cs H4`CH2C(C02H)2 CH 2 CHCO 2 H CH2C(C02H)2 1 "Nape," the back of the neck, is of doubtful origin; it may be a variant of "knap," a knob or protuberance.

It is a colourless solid, which melts at 80° C., and boils at 218° C. It crystallizes in the monoclinic system; it is to be noted that aand 0-naphthol assume almost identical forms, so that these three compounds have been called isomorphous. It is insoluble in water, but is readily soluble in alcohol,, and ether. It has a characteristic smell, and is very volatile, distilling readily in a current of steam. It acts as a weak antiseptic. It is used for enriching coal gas, as a vermin killer, in the manufacture of certain azo dyes, and in the preparation of phthalic acid (q.v.). When passed through a red-hot tube packed with carbon it yields 0j3-dinaphthyl, (C 10 11 7) 2. It forms a crystalline compound with picric acid. It readily forms addition products with chlorine and with hydrogen; the dichloride, C10H8C12, is obtained as a yellow liquid by acting with hydrochloric acid and potassium chlorate; the solid tetrachloride, C,o 11 8 C1 4, results when chlorine is passed into naphthalene dissolved in chloroform. Numerous hydrides are known; heated with red phosphorus and hydriodic acid the hydrocarbon yields mixtures of hydrides of composition C10H10 to C10H20. Sodium in boiling ethyl alcohol gives the a-dihydride, C l otho (E. Bamberger, Ber., 1887, 20, p. 1705); and with boiling amyl alcohol the 0-tetrahydride, C10H12 (E. Bamberger, Ber., 1890, 23, p. 1561). The a-tetrahydronaphthalene is formed when naphthalene is heated with phosphonium iodide at 170°-190° (A. v. Baeyer). Structurally naphthalene may be represented as. a fusion of two benzene nuclei, the hydrogen atoms being numbered as in the inset / 8 1 formula 7(I/12; 1, 4, 5, 8 are a-positions, 2, 3, 6, 7 are 6 // 3 4 1 -5 or 4-8 5 diderivatives are ana, whilst 1-8 or 4-5 are peri (see Chemistry, Organic).

a-Nitronaphthalene, C10H,N02, is formed by the direct nitration of naphthalene. For its commercial preparation see 0. Witt, Die chemische Industrie, 1887, to, p. 215. It crystallizes in yellow needles, which melt at 61° C., and are readily soluble in alcohol. By the action of nitro-sulphuric acid it is converted into, a mixture of 1 . 5 and 1 . 8 dinitronaphthalenes (P. Friedlander, Ber., 18 99, 32, p. 3531). When heated with aniline and its salts it yields phenylrosindulin (German patent 67339 (1888)). (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. Lellmann and A. Remy, Ber., 1886, 1 9, p. 2 37), or with freshly prepared potassium cupronitrite on 0-naphthalene diazonium sulphate (A. Hantzsch, Ber., 1900, 33, p. 2 553). It crystallizes in small yellow needles which melt at 78° C. and are volatile in steam.

Sulphonic Acids

Two monosulphonic acids (a and 0) result by acting with sulphuric acid on the hydrocarbon, the a-acid predominating at low temperatures (80° C. and under) and the 0-acid at higher temperatures (170°-200° C.). They are crystalline, hygroscopic compounds and are employed for the manufacture of the naphthols. Numerous di- and tri-sulphonic acids are known.

a-Naphthoquinone, C10H602, resembles benzoquinone, and is formed by the oxidation of many a-derivatives of naphthalene with chromic acid. It crystallizes in yellow needles which melt at125° C. It sublimes readily, is volatile in steam and reduces to the corresponding dihydroxynaphthalene. (-Naphthoquinone is formed by oxidizing 2amino-a-naphthol (from 0-naphthol-orange by reduction) with ferric chloride. It crystallizes in red needles, which melt at 115° C; it has no smell and is non-volatile (cf. phenanthrenequinone).Alizarin black,C l oH 4 (OH) 2 0 2 NaHS03, the sodium bisulphite compound of 7.8 dioxy-anaphthoquinone, is a dyestuff used for printing on cotton in the presence of a chromium mordant The naphthoquinone is prepared by the action of zinc and concentrated sulphuric acid on a-dinitronaphthalene. A 2.6 naphthoquinone results on oxidizing 2.6 dihydroxynaphthalene with lead Or Hydroxynaphthalenes, C 1 oH 7 OH, the naphthalene homologues of the phenols. The hydroxyl group is more reactive than in the phenols, the naphthols being converted into naphthylamines by the action of ammonia, and forming ethers and esters much more readily.

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. Fittig and H. Erdmann, Ann. 1885, 227, p. 242): C 6 H 5 CH: CH. CH2C02H C 10 H 7 OH+H 2 O. It forms colourless needles which melt at 94° C.; and is readily soluble in alcohol, ether, chloroform, and caustic alkalis. It is volatile in steam. With ferric chloride it gives a dark-blue precipitate of a-dinaphthol, HO C10H6 C10H6. OH. Alkaline potassium permanganate oxidizes it to phenyl-glyoxyl-ortho-carboxylic acid, H02CC6H4CO. CO 2 H. It is reduced by sodium in boiling amyl alcohol solution to "aromatic" tetrahydro-a-naphthol (reduction occurring in the ring which does not contain the hydroxyl group). When heated with hydrazine hydrate at 150° C. it gives a-naphthyl hydrazine, C 1 oH 7 NHNH 2 Hoffmann, Ber., 1898, 31, p. 2909). Nitric acid converts it into nitro-compounds, which are occasionally used for dyeing silk and wool.

Martius yellow, C10H5(N02)20Na H20, the sodium salt of 2.4 dinitro-a-naphthol (for notation see Naphthalene), is prepared by the action of nitric acid on a-naphthol -2.4-disulphonic acid. It forms orange-yellow plates and dyes wool a golden yellow (from an acid bath). Naphthol yellow S., C10H4(ONa) (NO 2) 2 S0 3 Na, prepared by the action of nitric acid on a-naphthol - 2.4. 7 - trisulphonic acid, is an orange-yellow powder which dyes wool and silk yellow (from an acid bath).

Numerous mono-, diand trisulphonic acids of a-naphthol are employed in the preparation of azo dyes. The most important is Nevile and Winther's acid, C 1 aHe(OH)(SO 3 H)(I. 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)). It melts at 170° C., and is readily soluble in water. With ferric chloride it gives a blue coloration.

0-Naphthol, C 1 oH 7 OH, prepared by fusing sodium 0-naphthalene sulphonate with caustic soda, crystallizes in plates which melt at 122° C. With ferric chloride it gives a green colouration, and after a time a white flocculent precipitate of a dinaphthol. With sodium in boiling amyl alcohol solution it gives a mixture of alicyclic and aromatic tetrahydro-/3-naphthols (E. Bamberger, Ber., 1890, 2 3, p. 1 97). When heated with ammonium formate to 150° C. it forms f3-napht!iylamine. With nitrosodimethylaniline hydrochloride it forms Meldola's Blue (dimethylaminonaphthophenoxazonium chloride), C18H15N20C1 (R. Meldola, Ber., 1879, 12, p. 2065).

The 0-naphthol sulphonic acids find extensive application in the colour industry. The most important members are shown in the table: - peroxide.




2- oxy-8-sulphonic

(Baeyer's acid)

From 0-naphthol and concen-

trated sulphuric acid at

50 0 -60° C.

Sodium salt soluble in

strong alcohol.


(Schaffer's acid)

From 0-naphthol and concen-

trated sulphuric at too° C.

Sodium salt insoluble in


. 2-oxy-7-sulphonic


By fusion of naphthalene 2.7-

disulphonic acid with caustic

soda at 200 0 -250° C.

Very soluble in water

and alcohol.

2- oxy-3.6-disulphonic


Both R- and G-acid from 0-

naphthol and concentrated

sulphuric acid at too°-


The sodium salts separ-

ated by crystalliza-

tion. R-salt insoluble

in alcohol; G-salt


2- oxy-6.8-disulphonic


2- oxy-3.6. 8-trisulphonic

From 0-naphthol and fuming

sulphuric acid at 140°- 160 °C.

Alkaline solutions show

green fluorescence.

a-Naphthoic acid, C 1 oH 7 CO 2 H, is formed by hydrolysis of the nitrile, obtained by distilling potassiuma-naphthalene sulphonate with potassium cyanide (V. Merz, Zeit. f. Chemie, 1868, p. 34), or by heating the sulphonate with sodium formate (V. Meyer, A nn., 1870, 156, p. 274). It forms needles which melt at 160° C. (3-Naphthoic acid, obtained b y boiling 0-methylnaphthalene with dilute nitric acid, or by hydrolysis of its nitrile (formed when formyl-0-naphthalide is heated with zinc dust), crystallizes from alcohol in needles which Nitrosonaplithols or naphthoquinone-oxames, C 1 oH 6 (OH)(NO) or melt at 184° C. C 1 oH 6 (: NOH): 0. Two are known, namely 4-nitroso-a-naphthol or 13; a-naphthoquinone-oxime, formed by the action of nitrous acid on a-naphthol or of hydroxylamine hydrochloride on a-naphthoquinone (H. Goldschmidt and H. Schmidt, Ber., 1884, 17 p. 2064); and 2-nitrouo-a-naphthol (, -naphthoquinone-oxime), formed by the action of hydroxylamine hydrochloride on 13-naphthoquinone.

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