251 POPE : FLUORONE DERIVATIVES. PART Ir.

XXVI I I .-Flu or one Derivatives. Par t ]I. Resorcinol- benxein.

By FRANK GEORGE POPE. RESORCINOL-BENZEIN is the name which was originally given by Doebner t o the compound he obtained by the condensation of resorcinol with benzotrichloride, when the reacting components were heated together for some hours a t 180-190° (Annalen, 1883, 217,

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252 POPE : FLUORONE DERIVATlVES. PART IT.

234). The empirical formula C,,H,,OQ was assigned t o the benzein, and the reaction was considered t o take place in the following manner :

C7H5C13 + 2C6H602 = 2HCl+ C,9H1504Cl, the intermediate chloro-derivative so formed being expected t o yield, by exchange of its chlorine atom f o r a hydroxyl group, a tetrahydroxytriphenylcarbinol :

C19H1504C1 + HOH = HCl + CI,H,,05. Apparently, however, anhydride f orination takes glace, and

resorcinol-benzein is produced : 2ClQH,504C1 + H 2 0 = 2HC1+ C3SH3009,

and Doebner considers that structurally i t may be represented by the expanded formula :

[CI$%(OH)~’C(OH) (G3Hd *C&%(OH)]2O* The benzein was described as crystallising from a mixture of

alcohol and glacial acetic acid in large crystals, exhibiting a violet- red reflex. They remained unaffected when heated to looo, but on raising the temperature to 130°, two molecules of water were lost, and analysis of the residual compound pointed to the composition C3,H,,07. No definite results were obtained either on acetylation or bromination.

Somewhat later, Cohn ( B e y . , 1891, 24, 2064; J . p r . Chem., 1893, [ii], 48, 387) obtained the same compound by the condensation of benzoic acid with resorcinol in the presence of zinc chloride, and stated that it formed an unstable compound with hydrochloric acid, and yielded with bromine a series of different bromo- derivatives, according to the amount of halogen employed and the temperature a t which the reaction was carried out.

Here the matter rested for some time, until Kehrmann (Ber., 1908, 41, 3442; 1909, 42, 873) pointed out that resorcinol-benzein was probably identical with the 3-hydroxy-9-phenylfluorone that he had obtained from the product of the action of benzotrichloride on acetyl-m ~aminophenol in nitroberizene solution. I n confirmation of this idea he prepared the benzein by Doebner’s method, and working with a highly purified product showed that its molecular weight agreed with that of 3-hydroxy-9-phenylfluorone (C,gH1203), and that on methylation with methyl sulphate, the methyl ether of the Auorone was obtained. Pope and Howard (T., 1910, 97, 1025) also drew attention t o the fact that the benzein might be considered as ideghical with Kehrmann’s 3-hydroxy-9-phenyl- fluorone.

H. v. Liebig (J. pr. Chem., 1908, [ii], 78, 534) has, however, objected to Kehrmann’s views, and supports the older Doebner

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POPE : FLUORONE DERIVATIVES. PART 11. 253

view, considering that in the preparation of the benzein from benzoic acid and resorcinol, benzoic anhydride may be used in place of the acid, the reaction then proceeding:

the compound thus obtained being Doebner's C3,H2,07. Numerous fresh derivatives of the benzein were described, amongst others being an anhydro-compound, C,6H520,3,C2H,*OH, formed by the action of ammonia on the benzein, a second anhydro-compound, C,6H,,0,4,CH3*C02H, obtained by heating the benzein with glacial acetic acid, a barium salt, C7,H4,0,,Ba,, a hydrochloride, C7,H,,0,,,4HC1, a compound, C3,H,,0g (m. p. 147*), formed by fusion of the benzein with an alkali hydroxide, an acetyl derivative, C,gH,20(O~CO*CH3)2,C2H5*OH, and a second acetyl compound, C3sH2,03(O*CO*CH3)4, prepared when the acetylation was carried out in the presence of zinc dust.

In 1912 v. Liebig (J. pr. Chem., 1912, [ii], 85, 97, 241) published two further communications dealing with the benzein, in which no reference is made to the two different anhydro-compounds obtained previously. Using the Doebner method of synthesis, he concludes that the reaction mixture contains a-resorcinol- benzein, C19H1203, @-resorcinol-benzein, (C19H1203)3,C2H5*OH, and y-resorcinol-benzeh, (ClgHl,03)4,H20,C2H,*OH, and the dihydroxy- benzophenone compound of the y-benzein, of the composition

The a-compound is considered as identical with Kehrmann's 3-hydroxy-9-phenylfluorone, whilst the P- and y-benzeins are formu- lated respectively as :

~ C ~ 9 ~ 1 2 0 ~ ~ 2 ~ H 2 0 ~ C 1 ~ H 1 ~ 0 ~ ~

OH 0

/\/\/\OH

/\

B.

Ph OEt OH OH

0 0 0

Using the Cohn method of synthesis, a 8-benzein, ( C,9E1203,R20)z, is also described, whilst the compound C38H3oOg (m. p. 147O), mentioned in the earlier paper, is now recognised as 2 : 4-dihydroxy- benzophenone.

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254 POPE : FLUORONE DERIVATIVES. PART IT.

I n the portion of v. Liebig’s paper dealing with his practical details, the term resorcinol-benzein is used very indiscriminately without reference to whether it applies to the a-, p-, y-, o r $-forms, and it is described as crystallising from nitrobenzene in red needles, having the composition (C,gH1203)4,3H20,C,H,*N02, and from aniline in dark red needles with a blue reflex, having the com- position (C,9H,20,)4,C6H,*NH2. These two compounds contain respectively 1-05 and 1.12 per cent. of nitrogen, and the following analytical data are given:

0*1128 gave 1.1 C.C. N, a t 21° and 722 mm.

0.1092 gave 1.5 C.C. N, a t 15O and 724 mm.

N=1*07.

N=1*55. N (calc.) = 1-05.

N (calc.) = 1.12.

results which, seeing the small quantity of substance taken, and the consequent amount of nitrogen obtainable, may be considered as open to a considerable amount of doubt, whilst the origin of the water of crystallisation ( !) is not apparent.

Various hydrochlorides are also described, the a-benzein yielding one of the composition C,gH,203,HCI; the p-, one of the composition (C,SH,20,)3,3HCl,C,H5*OH ; and the y-, one of the composition (C,g13[,203)4,4HC1,H20. The following observations may perhaps be offered with regard to the /3- and y-benzeins. The 8-form having the composition (C,gH,203)3,3C2H,*OH, when heated t o 140°, loses two molecules of aTcohol, and since the third molecule is difficult t o remove, the product obtained is considered as an ether-like com- bination of the benzein and alcohol, namely :

OH 0 EX 0 1 0 0 0 1 0

OH/\/\/\

CPh C CPh /\

P h OEt

but it is difficult to see why the ethoxy-group should be attached in this way, and no reason is given for affixing it in the position shown. When heated with alcoholic ammonia and the excess of ammonia is subsequently removed, it is said to yield a compound of the composition (ClgH,203)3,H,0,2C2H5*OH, which a t 140° loses water and alcohol, giving (C19H1203)3,C2H5*OH, finally passing at 240° into (c1gH&3)3.

With regard to the y-benzein, obtained by the action of alcoholic ammonia on dihydroxybenzophenone-y-resorcinol-benzein, this is

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POPE : FLUORONE DERIVATIVES. PART 11. 255

represented as (ClgHlZO3),,2HzO,C,H5~OH. A t water-bath tem- perature, by loss of water, i t passes into the compound

which loses alcohol when heated to 140°, yielding (C,,H120,),,H,0 or

0 0 0 0 0 0

(C,,H,20,)4,H,0,CZH5'0H,

OH OH

I I I I I I I l l v\<y V>Q/ PhC--0---

and finally, a t 240°, the last molecule of water is removed, and the anhydrous product, C19H1203, results. It seems curious that, on heating, the water molecule should be removed before the alcohol molecule, and that v. Liebig in this instance does not make use of an ether formulation t o explain the tenacity with which the alcohol molecule is held, whereas such a method was adopted with the &compound.

With the object of trying to decide between the conflicting opinions of Kehrmann and v. Liebig, resorcinol-benzein was pre- pared by the Doebner method, and the following results were obtained. The crude product, when boiled with water, yielded an aqueous extract containing benzoic acid, some 2 : 4-dihydroxybenzo- phenone, unchanged resorcinol, and a small quantity of a red colouring matter which was not further examined. The residual solid was digested with dilute ammonia and the mixture filtered, when a reddish-coloured residue was left. This is apparently the benzoyl derivative of the benzein, since it is insoluble in cold alkali, and on hydrolysis by means of mineral acid is decomposed very slowly with formation of benzoic acid.

The ammoniacal filtrate was acidified with acetic acid, and the precipitated solid purified by conversion into its hydrochloride. The hydrochloride was dissolved in ammonia, the base then pre- cipitated by the addition of acetic acid, and finally recrystallised from a suitable solvent.

It was a t first thought that by fractional crystallisation of the hydrochloride, two isomerides were obtained, but on liberation of the base from the two specimens, compounds of identical melting points were produced, and when a mixed melting point of the two specimens was taken, no depression was observed. Moreover, on fusion of the two specimens wifh an alkali hydroxide, both yielded 2 : 4-dihydroxybenzophenone, and thus apparently only one product of reaction is produced.

The resorcinol-benzein so prepared is identical with Kehrmann's 3-hydroxy-9-phenylfluorone, as is shown by the analytical data

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256 POPE : FLTJOROKE DERIVATIVES. PART 11.

obtained from the base, its hydrochloride, the sodium and barium salts, the acetyl derivative, and the acetyl derivative obtained on acetylation in presence of zinc dust. No trace of v. Liebig's various hydrochlorides was observed, and the same analytical results were produced whatever solvents were used for recrystallising the benzein. Liebig's anhydro-compounds could not be obtained either by the action of alcoholic ammonia or acetic acid; in each case the product formed gave tEa melting point of the unchanged benzein and furnished correspmding data on analysis, whi1,st no depression of melting point was observed on mixing the so-called anhydro- compounds with a specimen of the benzein.

I n order to obtain confirmatory evidence of the fluorone structure of the benzeiD, i t was subjected to the action of phosphorus penta- chloride,, when the 3 : 6-dichloro-9-phenylxanthonium chloride obt,ained by Howard and Pope (T., 1911, 99, 550) from the action of the pentachloride on 3-hydroxy-9-phenylfluorone was produced, the identity being further established by the conversion of the xanthonium chloride into 3 : 6-dianilino-9-phenylxanthenyl chloride and the corresponding 3 : 6-di-~-naphthylamino-compound on con- densation with aniline and P-naphthylamine respectively.

These facts would seem to justify Kehrmann's view as to the structure of resorcinol-benzein, and in the annexed table the formulze of the various author are contrasted.

Resorcinol- henzein ............ a- Kesorcinol-benzein ............ B-Elesorcinol- benzein ............ .y-Kehol.ciilol-l-lenzAin ............ 8-Resoi ci ri ol-be1 t zein ............ Anhydroresorcinol-bcnzein ( I )

9 9 9' (11) Hydrochlorides :

a .............................. 8 .............................. y ..............................

Barium salt ........................ Acetyl derivative .............. Reduced acetate ............... Alkali fusion .....................

products obtained by v. Liebig and the

H. v. Liebig. F. G . Pope.

I 'OH j

I

EXPERIMENTAL.

For the preparation of resorcinol-benzein, the method adopted by Kehrmann and Dengler (Ber., 1909, 42, 873) was used, and the product obtained was purified by means of its hydrochloride.

It was thought that possibly the hydrochloric acid solution from which the hydrochloride of 3-hydroxy-9-phenylfluorone was

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FOPE : FLUORONE DERIVATIVES. PART 11. 257

originally obtained might contain an isomeride, conceivably of the structure :

0

and with the object of ascertaining whether such were the case or no, the acid solution wap concentrated, and the crystalline residue obtained subjected t o purification by Kehrmann's method. The base obtained was, however, identical with 3-hyclroxy-9-plienyl- fluorone, and when the two were mixed, no depression of maiting point could be noticed, so that apparently only one product of the fluorone type is formed.

Resorcinol-benzein is readily soluble in hot nitrobenzene, aniline, or pyridine, but sparingly so in alcohol. From the three former solvents it crystallises in small, red needles, which melt a t 330-331O (Found, C=79*29; H=4.25. Calc., C=79.17; H=4*17 per cent.).

The hydrochloride, C19H120,,HC1, is obtained by dissolving the base in alcohol and adding concentrated hydrochloric acid to the solution (see above). It crystallises froin alcoholic hydrochloric acid in golden-yellow needles :

0.2240 gave 0.5748 CO, and 0.0826 H20. 0.1747 ,, 0.077 AgC1. C=70*0; H=4*09; C1=10*90. C19H,,03,HC1 requires C = 70.25 ; H = 4.01 ; C1= 10-94 per cent.

The sodium salt is prepared by suspending the base in s;ater, and adding to the suspension one equivalent of sodium hydroxide also dissolved in water. A deep red solution, showing a yellow fluorescence, is produced, and on concentration the sodium salt separates in very small, red needles:

0.2838 gave 0.0652 Na,SO,. Cl,Hl103Na requires Na = 7-42 per cent.

v. Liebig states that a soluble barium salt, C,,H,,O1,Ba, (Ba = 32.35 per cent.), is formed when resorcinol-benzein is heated with baryta solution. On repeating this experiment i t was found that the benzein is almost insoluble in cold baryta solution, but that on boiling it appears t o dissolve, and a barium salt, in an impure condition, or possibly a basic salt, is formed. If, however, the sodium salt is first prepared and barium chloride added t o its aqueous solution, a bright red precipitate of the barium salt of the fluorone is immediately produced. This was collected, well washed with hot water, and dried:

Na = 7.44.

VOL. cv. S

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258 POPE : FLUORONE DERIVATIVES. PART 11.

0.1253 gave 0.0408 BaS04. (C19H,,03),Ba requires Ba = 19.27 per cent.

The acetyl derivative, C,gH,,02-O*CO*CH,, was prepared by heating 5 grams of the benzein with 20 grams of acetic anhydride and 5 grams of anhydrous sodium acetate for four hours. The mixture was then poured into cold dilute alcohol, and warmed on the water-bath until the excess of the anhydride was destroyed. The residue was collected, washed, dried, and crystallised from alcohol or acetic acid, separating from the solvent in red needles:

Ba = 19.14.

0.1449 gave 0.4046 CO, and 0.057 H,O.

By carrying out the acetylation in the presence of zinc dust, the

C=76*15; H=4*37. C,,R,,O, requires C = 76.31 ; H = 4.27' per cent.

colourless 3 : 6-dihydrozy-9-phenylzanthen diacetate is obtained : 0

and on crystallisation from alcohol, separates in colourless needles, which melt a t 175O:

0.1048 gave 0.2840 CO, and 0.0436 H20. C,,H,,O, requires C = 73-80 ; H = 4-81 per cent.

According to v. Liebig, a compound which he designates as anhydroresorcinol-benzein, C,,H,,O,,,C,H,*OH, is obtained when the parent substance is heated with alcoholic ammonia. In order to test this statement, 4 gram? of the benzein were heated on the water-bath for two days with successive quantities of alcoholic ammonia, the product thoroughly dried, and compared with the original benzein, with the following results :

C = 73.91 ; H =4*62.

Besominol- benzcin. Red needles, m. p. 330-3.31".

Hydrochloride, yellow.

A nh ydroreso rciii o 1 - benze in. Red needles, m. p. 330-331".

No depression of m. p. on inixiiig with original substancc.

Hydrochloride, yellow.

Analysis of the so-called anhyclro-compound gave the following

0.1758 gave 0.5084 CO, and 0.0652 H,O.

v. Liebig's anhydro-compound would require C = 74.88 ; H = 4*64 per cent. It would thus seem apparent that alcoholic ammonia is without action on resorcinol-benzein a t water-bath temperature.

Again, a second anhydro-compound, C,,H,O,,,CH,*CO,R, is said to be formed on heating the benzein with glacial acetic acid. This experiment was repeated by heating the benzein for twelve hours

data : C=78.88; H=4*12.

C1gHI2O, requires C = 79.17 ; H = 4-17 per cent.

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POPE : FLUORONE DERIVATIVES. PART 11. 259

with the acid. It melted a t 330-331°, and was in all respects identical with the unchanged benzein :

The product obtained was collected and dried.

0.2667 gave 0‘7691 CO, and 0*1006 H,O. C=78.65; H=4.19. C1,H,,O3 requires C = 79.17 ; H = 4.17 per cent.

C,,H,Ol,,CH,*CO,H requires C = 74-88 ; H =4.64 per cent. In order further to establish the identity of the benzein with

3-hydroxy-9-phenylfluorone, the reaction between the benzein and phosphorus pentachloride was examined. For this purpose 5 grams of the benzein were dissolved in 20 grams of phosphoryl chloride and warmed on the water-bath, with the gradual addition of 10 grams of phosphorus pentachloride. The blood-red liquid obtained was warmed until all the pentachloride dissolved, allowed to remain for five minutes, and then poured into 300 C.C. of light petroleum. The yellow precipitate obtained was collected, well washed with light petroleum, and dried in a vacuum. It is insoluble in non- hydroxylic solvents, but readily decomposes in the presence of hydroxylic solvents. A chlorine estimation served to establish its identity with the 3 : 6-dichloro-9-phenylxanthonium chloride described by Howard and Pope (T., 1911, 99, 550) (Found, C1= 29.06.

Confirmation of this result is seen in the reaction of the above chloro-derivative when brought into contact with aniline and with 8-naphthylamine. I n the first case 5 grams of the dichlorophenyl- xanthonium chloride were heated for five minutes with 25 C.C. of aniline, and the resulting paste was added t o 200 C.C. of water, the whole rendered alkaline, and distilled in a current of steam t o remove the excess of aniline. The residue was acidified, the pre- cipitate collected, well washed with water, and dried. For purifi- cation, the bluish-purple solid was recrystallised from alcohol, separating from the solvent in very small needles, which dissolve in alcohol to a purple solution. Analysis showed that the substance obtained wa3 identical in composition with the dianilinophenyl- xanthenyl chloride obtained fsom 3-hydroxy-9-plienylfluorone (Found, C = 78.60 ; H = 4.6 ; C1= 7.28. Calc., C = 78-39 ; H = 4-84 ; Cl=7.48 per cent.).

Similar results were obtained by the condensation of the dichloro- xanthonium chloride with B-naphthylamine, the xanthenyl chloride formed recrystallising from nitrobenzene in small crystals showing a fine bronze reflex, and giving analytical data corresponding with the xanthenyl chloride obtained similarly from 3-hydroxy-9-phenyl- fluorone (Found, C1= 5.97.

From the above results it thus appears that resorcinol-benzein as obtained by Doebner method is identical with Kehrmann’s

Calc., C1= 29.49 per cent.).

Calc., Cl = 6-18 per cent.).

s 2

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260 WORLEY: THE SURFACE TENSION OF MIXrURES. PART I.

3-hydroxy-9-pl1enylfluorone, and is not a mixture of various forms, since the derivatives obtained by working with the two compounds are the same in both cases.

On fusion with alkali hydroxides, or on boiling with a moderately concentrated solution of potassium hydroxide, the benzein yields resorcinol and 2 : 4-dihydroxybenzophenone. To recover the latcer, the fusion was acidified with hydrochloric acid and filtered. The precipitated matter was extracted with cold alcohol, the alcoholic solution evaporated to dryness, and the residue repeatedly re- crystallised from hot water. I n this manner, pale yellow needles, melting a t 143-144O, are obtained. This is the melting point of 2 : 4-dihydroxybenzophenone, and analysis furnished data confirm- ing this conclusion (Found, C = 72.98 ; H = 4.7. Calc., C = 72.90 ; H = 4 . 7 per cent.)."

I n conclusion, I desire to express my thanks to Mr. E. Turner, B.Sc., for his help in the practical work, and to the Research Fund Committee of the East London College for a grant to defray expenses.

EAST LONDON COLLEQE.

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