HYDROXYNAPHTHOIC ACIDS. PART I. 1641

C'LXXXIV.-Hydroxyn~phlhoic Acids. Part I . By FRANK ALBERT ROYLE and JACK ARNOLD SCHEDLER.

OF the seven theoretically possible monohydroxy-derivatives of a-napht'hoic acid, only four appear to have been described, namely, 2-hydroxy-a-naphthoic acid, m. p. 158" (Kauhann , Ber., 1882, 15, 506; Schmitt and Burkhard, Ber., 1887, 20, 2701), 4-hydroxy- a-naphthoic acid, m. p. 183-184" (Heller, Ber., 1912, 45, 674), 5-hydroxy-a-naphthoic acid, m. p. 219" (Friedlander, Heilpern, and Spielfogel, Mitt. tech. Gewerbe Mzlseums Wein, 1898, 8, [ll and 121,316 ; see also J . SOC. Chem. Ind., 1898,17, 836), and 8-hydroxy- a-naphthoic acid, m. p. 169" (Ekstrand, J. pr. Chem., 1888, [ii], 38, 278).

In addition to the above, the chemical literature contains refer- ences to three other hydroxy-a-naphthoic acids of undetermined constitution. Battershall (2. Chem., 1872, [ii], 7 , 673 ; Annulen, 1873, 168, 144) sulphonated a-naphthoic acid and isolated from t'he products two isomeric monosulphonic acids which he distin- guished by the prefixes a and P. On fusion with potlassium hydr- oxide, the a-sulphonic acid gave a hydroxy-a-naphthoic acid melting a t 234-237", whilst the p-sulphonic acid did not yield a pure product.

Stumpf (Annulen, 1877, 188, 1) repeated Battershall's work, and in addition to the so-called a- and p-sulphonic acids he isolated a third monosulphonic acid, to which he prefixed the symbol y. He fused the p- and 7-monosulphonic acids with potassium hydroxide and obtained the corresponding hydroxy-a-naphthoic acids, which melted a t 243-247" and 186-187", respectively.

The only attempt made by Stumpf to determine the constitution of these hydroxynaphthoic acids was by distillation with lime; he found that the hydroxynaphthoic acid derived from the a- sulphonic acid yielded a-naphthol, whilst those obtained from the p- and 7-sulphonic acids yielded p-naphthol.

Three a-hydroxy-a-naphthoic acids are possible, namely, the 4-, 5-, and 8-hydroxy-acids, and, as has been previously mentioned, all these have been prepared by other and apparently trustworthy methods, and melt, respectively, a t 183-184", 219", and 169". If we take these melting points as accurate-and there is good reason to believe that they a r e t h e n the a-acid of Battershall and Stumpf, which melted a t 234-237", was not an a-hydroxy-a-naphthoic acid as they state, but either had a different constitution or was a very impure substance.

Again, Stumpf's p- and y-acids, being P-hydroxy-a-naphthoic

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1642 ROYLE AND SCHEDLER:

acids, might be any of the 2-, 3-, 6-, and 7-hydroxy-a-naphthoic acids.

The last three are unknown, and it is scarcely possible that either the p- or the y-acid could be identical witch 2-hydroxy-a-naphthoic acid-which is the only p-hydroxy-a-naphthoic acid that has been described-since the melting points are so widely divergent , and thc constitution of this acid is well established.

With these facts in mind, the present authors proposed to prepare the 3-, 6-, and 7-hydroxy-a-naphthoic acids and thus attempt to establish the identity of Stumpf's P- and y-acids.

Two of the desired acids-the 6- and the 7-hydroxy-acid, were obtained, respectively, from a-naphthylamine-6-sulphonic acid and a-naphthylamine-7-sulphonic acid by diazotising, proceeding through the cyano-sulphonic acid to t hc carboxy-sulphonic acid, and fusing this with potash.

6-Hydroxy-~-na~TLthoic acid, prepared in this manner, melts at 208-209", whilst the 7-hydroxy-a-naphthoic acid melts at 253-254".

3-Hydroxy- a-naphthoic acid was prepared in a similar manner from a-naphthylamine-3-sulphonic acid ; it melts a t 242-243".

From a consideration of these melting points it would appear a t first sight that Stumpf's p-acid, m. p. 245-247", might be identical with 3-hydroxy-a-naphthoic acid, m. p. 242-243". Stumpf, however, describes his P-acid as crystallising from water in bulky masses of needles, a description which agregs perfectly with the characteristics of 7-hydroxy-a-naphthoic acid, m. p.

Stumpf's y-acid, m. p. 186-187", might possibly be a very impure specimen of 6-hydroxy-a-naphthoic acid, m. p. 208-209".

The properties of the a-acid, as previously mentioned, do not appear to suggest those of any of the known a-hydroxy-a-naphthoic acids.

In order to obtain a definite decision on the question, the work of Battershall and of Stumpf has been repeated and thc p- and y-hydroxy-a-naphthoic acids of these workers have been proved to be impure specimens of 7- and 6-hydroxy-a-naphthoic acids, respectively. The a-acid has been definitely found to be pure 5-hydroxy-a-naphthoic acid, the melting point, 219", of this acid as given by Friedliinder, Heilpern, and Spielfogel (Zoc. cit.) being incorrect.

253-254".

E X P E R I M E N TAL.

Materials used.-The a-naphthylemine-6- and a-naphthylamine- 7-sulphonic acids were commercial products, and these were further purified in the laboratory before use.

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HYDROXYNAPHTHOIC ACIDS, PART I. 1643

a-Naphthylamine-3-sulphonic acid was prepared from the corn- mercial acid sodium salt of a-naphthylamine-3 : 8-disulphonic acid (C-acid) by boiling with 75 per cent. sulphuric acid for two hours (Kalle & Co., D.R.-P. 64979). On a small scale, it was found advisable to increase the proportion of sulphuric acid recom- mended in the patent, and 7 parts by weight of 75 per cent. sulphuric acid gave good results without excessive charring.

Diazotisation of a-Naphthylamine-3-, -6-, and -7-sulphonic Acids. -The a-naphthylaminemonosulphonic acid (23 grams) was dis- solved in an aqueous solution of sodium bicarbonate (9 grams) and the solution filtered to remove any insoluble impurities. The volumes of water which were found to give the most satisfactory results were 180 c.c., 100 c.c., and 60 C.C. in the case of the 1 : 7-, 1 : 6-, and 1 : 3-acid, respectively. The solution was cooled to about Oo, concentrated hydrochloric acid (65 c.c.) added rapidly, and the finely divided suspension diazotised by the gradual addition of sodium nitrite (7 grams in 20 C.C. of water) with stirring, the temperature being maintained below 5O-this is especially necessary with the 1 : 6- and 1 : 7-acids, but with the 1 : 3-acid the temperature may be slightly higher without the formation of undesirable com- pounds taking place. The diazonium chlorides separated in the case of the 1 : 6- and 1 : 7-acids as light brown, semi-crystalline solids, whilst the 1 : 3-diazonium chloride was canary-yellow and quite crystalline in character. The solutions were saturated with sodium chloride and filtered. The solid diazonium chlorides were washed with cold saturated salt solution and used in a damp condition.

l-Cyanonaphthalene-3-, -6-, and -7-sulphmic Acids.-The solid diazonium compound was added to a hot cuprous cyanide solution (50-60") prepared in the usual way,* and the mixture was sub- sequently warmed on the steam-bath for an hour. Concentrated hydrochloric acid was then added to the hot solution, the precipit- ated cuprous cyanide filtered off and washed with a little hot water, the washings and filtrate were evaporated to dryness, and the residue was extracted several times with 90-95 per cent. alcohol. The alcohol was evaporated and the nitriles were recrys- tallised from a small bulk of water, animal charcoal being utilised if necessary.

It was not easy to obtain these nitriles in a sufficiently pure state

* In preparing the cuprous cyanide solution, any unnecessary excess of potassium cyanide was avoided by adding dilute hydrochloric acid to the clear solution until a faint opalescence was detected. Unless this precau- tion was observed, the cyano-sulphonic acids were invariably contaminated with a purple impurity.

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1644 ROYLE AND SCHEDLER:

for analytical purpoLies, and they were usually hydrolysed before any analyses were made. 3-, 6-, and 7-Sulpho-a-naphthoic Acids.-The potassium salt of

the cyano-sulphonic acid (or the whole of the solution after the precipitation of the cuprous cyanide) was boiled with 10 per cent. aqueous potassium hydroxide until ammonia ceased to be evolved. Any final trace of copper was removed by passing hydrogen sulphide through the boiling, acidified solution, which was then filtered and evaporated until crystals began to appear. On standing, almost the whole of the desired potassium carboxynaphthalenesulphonate crystallised.

The crystalline character of all three potassium carboxynaphtha- lenesulphonates readily distinguished them from potassium or sodium chloride. They were usually sufficiently pure for the next stage of operations, but could, if necessary, be readily purified by recrystallisation from water.

I n the preparation of the salts, of which the following analyses were made, potassium or sodium salts were used throughout so as to avoid the formation of mixed salts. Xodium 1-carboxynaphthalene-3-sulphonate crystallises from water

or dilute acetic acid in small needles (Found : H20 = 6.3; Nal= 7.7. C11H70,SNa,H,0 requires H20 = 6.2; Na = 7.9 per cent.).

Potassium 1-carboxynaphthalene-6-sulphonate crystallises in microscopic needles from water or dilute alcohol (Found : H20 = 10.9 ; K = 11.7. C11H70,SK,2H20 requires H,O = 11.0 ; K = 12.0 per cent.).

Potassium 1 -carboxynuphthalene-7-sulphonate crystallises from water or dilute acetic acid in slender needles (Found : H20 = 10%; K = 11.8. Cl,H,0,SK,2H20 requires H20 = 11.0; K = 12.0 per cent .).

Fusion of l-Carboxynaphthulene-3-, -6-, and -7-sulphonates with Potassium Hydroxide.-The finely powdered, anhydrous sulphonate (1 mol.) was added gradually to fused potassium hydroxide at 260"; after each addition, the temperature was allowed to rise to 260" and the mass was well stirred. Having been finally heated a t 280" for about five minutes, the melt was cooled, dissolved in water, and almost neutralised with sulphuric acid, and from the solution, filtered if necessary, the hydroxy- a-napht hoic acid was precipitated by concentrated hydrochloric acid. The crude acid was purified by converting it into the sodium salt, the aqueous solution of which was boiled with animal charcoal and filtered. The hydroxy-a-naphthoic acid was then reprecipitated with hydro- chloric acid and recrystallised from boiling water.

6-Hydroxy-u-naphthoic acid is almost insoluble in cold water,

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HYDROXYNAPTITHOIC ACIDS. PART I. 1645

but it is readily soluble in boiling water, from which it crystallises in fine, silky needles meking a t 208-209". It is soluble in alcohol, ether, acetone, or warm glacial acetic acid, but much less soluble in benzene or chloroform. With ferric chloride, the aqueous solution gives a dark brown coloration. Dilute aqueous-alcoholic solutions of the sodium salt show a green fluorescence (Found : C = 70.1 ; H = 4.3. C,,H,O, requires C = 70.2; H = 4.2 per cent.). The acetyl derivative crystallises in needles from dilute acetic acid or toluene. It melts at 209-210" [Found : C = 67.7; H = 4.4; CO*CH, = 18.3. C,,H,O,(CO*CH,) requires C = 67.8; H = 4.3; CO*CH, = 18.6 per cent.]. The anilide * is almost insoluble in the usual organic solvents, but may be crystallised from acetic acid, from which it separates in short, glistening needles, m. p. 193-194" (Found : N = 5.5.

7-Hydroxy-a-naphthoic acid, in general properties, is very similar to the 6-hydroxy-acid. It is, however, less soluble in cold water, from which it crystallises in bulky masses of fine needles, m. p. 253-254". The ferric chloride coloration and the fluorescence are also very similar to those of the previously described acid (Found : C = 70.1 ; H = 4.5. C,,H,O, requires C = 70.2 ; H = 4.2 per cent.).

The acetyl derivative, m. p. 221-222", crystallises in long, transparent needles from dilute alcohol [Found : COCH, = 18.0. C,,H,O,(COCH,) requires COGH, = 18.6 per cent.]. The anilide, m. p. 209-210", forms small needles from acetic acid (Found: N = 5.1.

3-Hydroxy-cc-nap&hoic acid is even less soluble in water than either of the above acids. It crystallises from this solvent in short needles melting at 242-243". The ferric chloride coloration is reddish- brown and the fluoreseence of the dilute aqueous-alcoholic solution of the sodium salt is purple (Found : C = 70.1 ; H = 4.4. CllH,O3 requires C = 70.2 ; H = 4-2 per cent.).

The acetyl derivative, m. p. 169-170", crystallises in long, transparent needles from dilute alcohol [Found : COCH, = 18.2. C,,H,03(CO*CH,) requires COCH, = 18.6 per cent.].

C,,H,,O,N requires N = 5.3 per cent.).

C,,H1,02N requires N = 5.3 per cent.).

Sulphonation of u-Naphthoic Acid. In their sulphonations of a-naphthoic acid, Battershall and

Stumpf (Zoc. cit.) made use of fuming sulphuric acid of unspecified

* The anilides were prepared according to D.R.-P. 293897 (Chemische Fabrik Grie8heim Elektron), which describes a modification of Schoepff's method (Ber., 1892, 25, 2744). The hydroxynaphthoic acid, suspended in toluene, was treated with the requisite amount of aniline, and phosphorus trichloride was slowly dropped into the agitated mixture; the solution was finally boiled so as to complete the reaction.

3 K*

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1646 ROYLE AND SCHEDLER:

strength ; hence it was impossible to repeat their conditions exactly. Parallel results were, however, obtained by heating a-naphthoic acid (1 mol.) with 98 per cent. sulphuric acid (3 mols.) on the steam- bath for eight hours and converting the product into neutral barium salts by the usual method.

Separation of the a-, p-, and y-Sulphonic Acids.-Fractional crystallisation of the neutral barium salts failed to yield within a reasonable time more than one pure salt. This salt consisted of well-defined, transparent, hexagonal plat'es corresponding in general characters with Stumpf's a-salt. Conversion of the material remaining in the mother-liquors into acid barium salts resulted in the separation of the P- and 7-salts, but i t was found more expedient to convert the whole of the sulphonic acids into their acid barium salts in the first instance. On evaporation of this solution, the almost insoluble acid barium salt of the 7-sulphonic acid was first deposited-and was obtained pure by recrystallisation from boiling water. Further evaporation of the mother-liquors yielded one or two indefinite fractions of granular material and then two very characteristic fractions crystallising in balls of fine needles ; these undoubtedly consisted of the acid barium p-sulphon- ate, which Stumpf described as crystallising in " soft, voluminous, warty masses." The p-salt also was purified by recrystallisation from boiling water. The mother-liquors of the y- and p-salts were then made neutral with barium carbonate, and on further evapor- ation gave a good yield of the neutral a-sulphonate. The inter- mediate fractions and all mother-liquors were fully investigated and readily resolved into or-, p-, and 7-salts, no traces of other salt's being detected.

Conversion of the a-, p-, and 7-Salts into Hydroxy-a-naphthoic Acids.-The neutral sodium salts obtained from the preceding barium salts by the usual methods were fused with excess of potassium hydroxide ; the resulting hydroxy-a-naphthoic acids were isolated and purified in the manner described in the earlier part of this paper. In each case, the yields from the fusions were satisfactory and the hydroxy-a-naphthoic acids obtained had the following melting points (the figures in brackets are the m. p.'s recorded by Stumpf) : a-acid, m. p. 235-236" (234-237"), acetyl derivative, m. p. 202-203"; P-acid, m. p. 253-254" (243-247')' acetyl derivative, m. p. 221-222"; y-acid, m. p. 208-209" (186- 187"), acetyl derivative, m. p. 209-210".

From these figures it is clear that the p- and y-acids obtained by Stumpf were impure specimens of 7-hydroxy- and 6-hydroxy-a- naphthoic acids, respectively.

The or-acid had all the properties of Battershall and Stumpf's

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HYDROXYNAPIITIIOIC ACIDS, PART I. 1647

a-acid, although it failed to correspond with any of the three possible a-hydroxy-a-naphthoic acids, all of which had been previously described in the literature. Since 4-hydroxy-a-naphthoic acid cannot be obtained from 4-sulpho- a-naphthoic acid by fusion with potassium hydroxide owing to loss of carbon dioxide, and since 8-hydroxy- a-naphthoic acid readily yields an anhydride, the authors draw the conclusion that the a-acid must be 5-hydroxy- a-naphthoic acid, which had been described as melting a t 219" by Friedlander, Heilpern, and Spielfogel (Zoc. ci t . ) . In order to justify this con- clusion, a specimen of a-naphthylamine-5-sulphonic acid was converted into 5-hydroxy-a-naphthoic acid by the methods described above. The acid obtained in this way crystallised from hot water in long needles melt'ing a t 235-236", and gave an acetyl derivative melting a t 202". Further, the preparation of 5-hydroxy- a-naphthoic acid by Friedlgnder, Heilpern, and Spielfogel's method again yielded the same acid melting at 235-236", and there can be no doubt whatever that Battershall and Stumpf's a-acid was practically pure 5-hydroxy-a-naphthoic acid.

Summary. 1. 3-, 6-, and 7-Hydroxy-a-naphthoic acids have been prepared

and characterised. 2. The sulphonation of a-naphthoic acid with 98 per cent. sulph-

uric-acid at 100" has been shown to produce a mixt'ure of 5-, 6-, and 7-sulpho-a-naphthoic acids.

3. The so-called a-, p-, and 1-hydroxy-a-naphthoic acids of Stumpf and Battershall have been proved to be 5-, 7-, and 6- bydroxy-a-naphthoic acids, respectively.

4. 5-Hydroxy-a-naphthoic acid melts a t 235-236", and not at 219" as previously stated.

The authors desire to express their thanks to Professor Lapworth for his interest in this work.

TIXE UNIVERSITY, MANCHESTER. [Received, May tith, 1923.1

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