536 CROWTHER AND McCOMBlE: THE ACTION OF

MI.-The Action of Chlorine on Thymol and on m- C’resol.

By HORACE LESLIE CROWTHER and HAMILTON MCCOMBIE.

IN continuation of the study of the action of chlorine on iodo- phenols (Brazier and McCombie, T., 1912, 101, 968; King and McCombie, T., 1913, 103, 220), the authors investigated the action of chlorine on 6-iodothymol (I). It was found that this compound, on chlorination in carbon tetnchloride solution, readily lost iodine, and after chlorination for one to two hours, a compound, C,,H90Cl,, was obtained. On chlorination for a further period, a substance was obtained which proved to be a derivative of m-cresol. As the iodine was so easily displaced by chlorine from 6-iodothymol (I), the process evidently resolved itself into a chlorination of tliymol in the presenc6 of iodine, and, since not only thyinol derivatives resulted, but also m-cresol compounds, the authors have investigated the action of chlorine on these two substances, under different conditions of temperature, irr. different solvents, and in the presence nf several catalysts.

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CHLORINE ON THYMOI, AND OM M-CRESOL. 537

Very little seems to have been done with regard to the chlorination of thymol. By the action of sulphuryl chloride on thymol, Bocchi (Gazzetta, 1897, 26, ii, 403) and Peratoner and Condorelli (ibid., 1899, 28, i, 214) were able to prepare 6-chlorothymol (11); the same compound has also been obtained by Robertson and Briscoe (T., 1912, 101, 1968) by the direct action of the theoretical quantity of chlorine on thymol. Blum (Zeitsch. physiol. Chem., 1892, 16, 518), by boiling 2 : 6-dichlomthymolglycuronic acid with sulphuric acid, isolated 2 : 6-dichlorothymol (111). I n a paper entitled (( Etudes sur l’essence de thym,” Lallemand (Ann. Chim.

OH OH OH

(1.) (11.1 (111.) Phys., 1857, [iii], 49, 148) describes a trichloro- and a pentachloro- thymol, both of which he obtained by the direct chlorination of thymol. The pentachloro-coxpound is described as decomposing a t 200° with the formation of propylene and tetrachloro-m-cresol.

Several benzenoid compounds, containng the isopropyl group, on chlorination and bromination, appear to lose that group very easily. Thus Dahmer, in a paper on the nitration of broniophenols (Annalen, 1904, 333, 346), found it impossible to introduce more than two atoms of bromine into the thymol molecule, even by acting on it with a large excess of bromine. The product which he obtained, employing excess of bromine, was 2 : 4 : 5 : 6-tetrabromo- mcresol (IV). A similar elimination of the isopropyl group was

OH r

(IT. 1 (V. 1 (VI. 1 also noticed by Arnand (Compt rend., 1898, 126, 1284). This experimenter found that cymene (V), on bromination in the presence of aluminium bromide, gave rise to pentabromotoluene (VI), whilst thymol under similar conditions yielded 2 : 4 : 5 : 6-tetra- bromo-m-cresol (IV).

1. Direct Chlorination of Thymol. I f solid thymol is subjected to the action of chlorine, it is a t

once attacked with the evolution of much hydrogen chloride. The thymol is liquefied by the great amount of heat evolved, and the colour of the solution changes to dark red, which gradually lighten8

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538 CROWTHEE AND McCOMBIE: THE ACTION OF

on continued chlorination. Finally, a yellow, crystalline substance is obtained, which is identical with the compound described by Lallemand (Zoc. c i t . ) as 2 : 5 : 6-trichlorothymol (VII). From the fact that this trichloro-compound did not dissolve in sodium hydroxide, but was slowly decomposed by it on warming, and, from the further fact that no acyl derivatives of it could be obtained, it was suspected that this substance was not trichlorothymol, but was 2 : 4 : 4-trichloro-3-methyl-6-isopropyl-A2 :5-cycZohexadienone (VIII). A further argument for this constitution of the substance is furnished by its behaviour towards potassium iodide. If the compound is treated with potassium iodide in acetic acid solution, iodine is a t once liberted, and the reaction can be followed quantitatively by titrating the iodine liberated with K / 10-sodium thiosulphate. It was found that two atoms of iodine were liberated

co /\ OH OH ECl EPra

CI/\P*@ CMe CH CI/)P,P M€?\)Cl \/ \/ Me/

c1 C

c1 c1 (VII.) (VII I.) (111.)

for every molecule of the trichloro-compound, and the equation representing the transFormation is as follows :

C,,H,,OCl, + 2KI = C,,Hl,C120K + KC1 + I,. From the potassium salt of the dichlorothymol which is produced

in this reaction, the acetic acid forms the free phenol (111), and, when the reaction mixture is poured into water, this compound separates as an oil. This compound is probably identical with the dichlorothymol described by Blurn (Zoc. c i t . ) , although the latter gives no boiling point for his compound. I n contradistinction to the dicliloro-compound, 2 : 6-dichlorothymol is readily soluble in potassium hydroxide, and, with methyl sulphate, yields a methyl derivative, thus establishing the existence of a hydroxyl group in its molecule. By leading chlorine into the oily 2 : 6-dichlorothymol, hydrogen chloride is evoIved, and the trichlorocydohexadienone is regenerated.

The so-called trichlorothy,mol is described, both in Beilstein’s (( Handbuch,” and in Richter’s “ Lexikon,” as forming an isomeric compound on treatment with sulphuric acid a t looo. This appears to be a mistake, for, on referring to Lallemand’s original paper, we find the statement made by him is that the trichlorothymol is transformed by the action of sulphuric acid a t looo into “l’acide phknique trichlor6.” The authors have repeated this reaction, and

/\ C1

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CHLORINE ON TRYMOL AND ON M-CRESOL. 539

have found that the trichloro-compound was very easily decom- posed by sulphuric acid a t looo, little or no charring took place, and the resulting compound was 2 : 4 : 6-trichloro-m-cresol (IX).

* This compound is dealt with later under the chlorination of m-cresol. The melting point of the “ isomeric trichlorothymol ” mentioned in Beilstein and of Lallemand’s “ acide ph6nique trichlor6” agrees well with that obtained by the authors for tri- chloro-m-cresol, namely, 46O.

This formation of trichloro-m-cresol by the action of sulphuric acid on trichlorornethylisopropylcyclohexadienone (VIII) must be brought about by the elimination of the isopropyl group and the migration of one of the chlorine atoms into the position occupied by the isopropyl group. A somewhat similar migration of halogen atoms in the thymol series has been noticed by Robertson and Briscoe (loc. cit.), who have shown that 6-chlorothymol (11), on bromination, yields a mixture of 6-chloro-2-bromothymol (X) and 2-chloro-6-bromothymol (XI). To explain this, these authors assume that an intermediate compound (XII) is formed, and that then the halogen wanders.

GO

The chlorination of thymol in carbon tetrachloride solution did not proceed very far, for the resulting product was an oil, probably dichlorothymol. ,From this yellow oil there separated sometimes, after the solution had remained for a long time, a few crystals of the trichloro-compound. Without the presence of a catalyst, the chlorination could, under no conditions, be carried further, than the trichloro-compound.

2. Chlorination of Thymol in Presence of Iodine.

If thymol is chlorinated for several hours a t the ordinary tem- perature, in dilute carbon tetrachloride or acetic acid solution, the first product that can be isolated is a small quantity of a penta- chloro-compound. This product, on gently warming in acetic acid or alcoholic solution, slowly liberated iodine from potassium iodide, but it was found impossible to follow the reaction quantitatively. The pentachloro-compound was insoluble in potassium hydroxide,

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540 CROWTHER AND McCOMBIE: THE ACTION OF

and formed no acetyl or benzoyl derivatives. It was decomposed by concentrated sulphuric acid a t 150-200°, with much charring and the formation of a small quantity of tetrachloro-m-cresol (XIII) . These reactions are analogous to those of the trichloro-compound, and the pentachloro-compound is most probably 2 : 4 : 4 : 5-tetra.- chloro-3-methyl-6-~-chloroisopropyl-h2~~-cycZohexadienone (XIV).

co co /\

\/

/\.

RCl GCl /\

OH fiC1 fi*CMe,Cl CI/\Cl CMe CCl CMe CCI

c c1 c1

(XIII.) (XIV.) (XV.)

It was found to be almost impossible to arrest the chlorination a t the stage of the production of this pentachloro-compound, especially in more concentrated solutions, as the isopropyl group was very readily eliminated with the production of m-cresol derivatives. The next product which was formed after the pentachloro- compound was 2 : 4 : 5 : 6-tetrachloro-m-cresol (XIII) , which separated from the concentrated carbon tetrachloride solution. This substance yielded both an acetyl and a benzoyl derivative, thus showing the presence of a hydroxyl group in the molecule; the compound did not liberate iodine from potassium iodide.

Tetrachloro-m-cresol is mentioned by Lallemand as being formed by the decomposition of pure pentachlorothymol, but the melting point of it, as given by that experimenter, appears to be very low.

Tetrachloro-m-cresol, on chlorination in carbon tetrachloride solution, in the presence of iodine, passed very readily into 2 : 4 : 4 : 5 : 6 -pentachlor0 - 3 - methyl-A2:5-cycZohexadienone (XV), which was found to be the chief and final product of the complete chlorination of thymol in the presence of iodine. The constitution of this compound was established by reactions similar t o those employed in the case of 2 : 4 : 4-trichloro-3-methyl-6-isopropyl- A2 :5-cycZohexadienone (VIII). It? liberated iodine very readily from potassium iodide in alcoholic or acetic acid solution, and, by titrating the iodine thus liberated, the reaction was followed quantitatively, and was found to agree with the following equation :

C7H30C15 + 2KI = C7H3C140K + KCI + 12. No acetyl or benzoyl derivatives could be obtained from this

substance, and the compound was easily attacked and decomposed by alkalis. On treatment with concentrated sulphuric ?cid a t looo, 2 : 4 : 4 : 5 : 6-pentachloro-3-methyl-A2:5-cycZohexadienone was

MJ,)Cl \/ c A.

Cl

c1 c1

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CHLORINE ON T H Y M O L AND ON M-CRESOL. 541

oxidised very readily to 2 : 4 : 5-trichlorotoluquinone (XVI). The identity of this last compound was established by a mixed melting- point determination with a specimen of the trichlorotoluquinone prepared by the oxidation of o-toluidine with sodium dichromate (compare Elbs and Brunschweiler, J . pr . Ciiem., 1896, [ii], 52, 539). Small quantities of 2 : 4 : 5-trichlorotoluquinone were also obtained by the prolonged chlorination (lasting for about ten days) of thymol in presence of iodine, in carbon tetrachloride solution.

3. Chlorination of Thymol in the Presence of Reduced Iron.

I n the hope of obtaining better yields of the pentachloro- derivative from thymol, the chlorination was carried out in the presence of a small quantity of reduced iron. The iron, however, seemed to have a much greater catalytic effect than the iodine. The solution to be chlorinated was a solution of thymol in carbon tetrachloride, a little reduced iron was added, and the mixture was cooled in a freezing mixture. The following results were obtained :

After twenty minutes, a n oil. After three-quarters to one and a-half hours, 2-: 4 : 6-trichloro-

After two to three hours, tefrachloro-m-cresol. After four hours and allowing the solution to remain in presence

of the iron overnight, tetrachloro-m-cresol and a small quantity of 2 : 4 : 5-trichlorotoluquinone.

If the chlorination took place a t the ordinary temperature, then, after three to four hours, there resulted pentachloromethylcyclo- hexadienone (XV).

#

m-cresol.

OH O H OH

(XIII). GO co /\

SC1 fiCl CMe CCI

/\ fiC1 ;C;lCl

-A CXe CCI \/ co

/\ c1 c1 (XV. 1 (XVI.)

Thus thymol, on chlorination in the presence of iron, even in an ice-cold solution, decomposed with the formation of bichloro-

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542 CKOWTHEK. AND McCOMBIE: THE ACTION OF

m-cresol and isopropyl chloride. The trichloro-m-cresol was also obtained by the direct chlorination of m-cresol, and will be dealt with later. The isopropyl chloride could not be isolated satisfac-, torily, as it could not be separated from the large excess of carbon tetrachloride, in which solvent the chloriliation was conducted. On distillation of the solution a fraction was obtained which seemed to be a mixture of isopropyl chloride and carbon tetrachloride of constant boiling point.

4. Chlorination of Thysrnol in the Presence of Alu11.1itaiurri-,~ercury.

This catalyst has a very similar effect on the chlorination to that exerted by the reduced iron, but the action was not nearly so vigorous as in the case of the latter. The first product which could be isolated in this case was 2 : 4: 6-trichloro-m-cresol.

5. Chlorination of m-Cresol.

When chlorinated, m-cresol passes directly to the 2 : 4 : 6-trichloro- compound. The chlorination was carried out under different con- ditions, namely, (1) in the presence of reduced iron in ice-cold solution; (2) by leading chlorine for six hours into boiling m-cresol; and (3) in carbon tetrachloride solution a t the ordinary tem- perature. All these three methods of chlorination gave, as first product, 2 : 4 : 6-trichloro-m-cresol. The first two methods gave very impure products, which required many recrystallisations before the substance was obtained in a pure state. After evaporating off the solvent, the third method was found to give by far the purest product.

A compound obtained by the direct chlorination of boiling m-cresol is described by Claus and Schweitzer (Ber., 1886, 19, 930) as dichloro-m-cresol. These experimenters give the melting point of their compound as 46*, which is identical with that of the trichloro-compound prepared by the authors. Many attempts have been made to prepare a mono- and a dichloro-m-cresol by chlorination for different periods of time in carbon tetrachloride solution. These all failed, for the first product which was invariably obtained was trichloro-m-cresol. The trichloro-m-cresol yields a methyl and an acetyl derivative, and, from analyses of these two compounds and also of the parent phenol, it seems evident that Claus and Schweitzer were mistaken.

Further chlorination of m-cresol in presence of a catalyst gave rise simply to the higher chlorination products which have been described earlier in dealing with the chlorination of thymol.

The following diagraw &ows the products which have been

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CHLORINE OX TIIYMOL AND ON M-CRESOL. 543

obtained, under different conditions, by the action of chlorine on thymol and on m-cresol. . OH 0 H

I /g .L co GO

/\ /\

\/ \/

flCl ECl y o 4 at ECl ECl CMe CCI 100" CMe CCI

CCI, co

EXPERIMENTAL.

2 : 4 : 4 : -Trichloro-3-methyl-6-isopropyl-A2 :5-cyclohexndienone, C,,H,,OCI, (VIII).

This compound was prepared by the direct chlorination of thymol without any solvent or catalyst. Under the influence of the chlorine the solid thymol gradually liquefied with a considerable evolution of heat, the liquid became dark brown, and then, on continued chlorination, this colour disappeared. The chlorination was stopped when the weight had increased by about two-thirds. A mass of yellow crystals separated when the liquid was allowed to remain a t the ordinary temperature for some hours; the crystals were collected and recrystallised from methyl alcohol, when the substance separated in bright yellow needles, which melted a t 63O :

C,,H,,OCI, requires C1= 42-01 per cent. is

readily soluble in acetic acid, acetone, ether, chloroform, or light petroleum in the cold, and also in hot alcohol. It is insoluble in potassium or sodium hydroxides, but is decomposed by them slowly

0.2022 gave 0.3418 AgC1.

2 : 4 : 4 - TrichEoro-3-methyl-6-isopropyl- @:5-~yclohezadienone

C1= 41.81.

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544 CROWTHER AND McCOMBIE: THE ACTION OF

on warming. The substance is also decomposed by concentrated sulphuric acid a t looo, with little or no charring, and the formation of 2 : 4 : 6-trichloro-m-cresol. The trichlorocyclohexadienone readily liberates iodine from a solution of potassium iodide in acetic acid solution, with the format'ion of 2 : 6-dichlorothymol. This reaction can be followed quantitatively if the liberated iodine is titrated rapidly in an ice-cold solution with N l 10-sodium thiosulphate. It was found that 0.3957 gram of substance gave 0.4080 gram of iodine ; the equation C,,H,,OC& + 2KI = C,,H,,C120K + KC1 + I, requires 0.3965 gram of iodine.

2 : 6-D~chZorotJ~ymoZ (111). This compound was prepared by Blum (Zoc. cit .) by heating

2 : 6-dichlorothymolglycuronic acid with sulphuric acid. We obtained it by treating 2 : 4 : 4-trichloro-3-methyl-6-isopropyl-

A2 :5-cycZohexadienone in acetic acid solution with excess of potassium iodide. After allowing the mixture to remain for a few minutes, it was poured into a solution of sodium thiosulphate t o remove the iodine, and the yellow oil which separated was extracted with ether, washed, dried over sodium sulphate, and distilled under diminished pressure, when the 2 : 6-dichlorothymol passed over a t 135O/ 12 mm. (Found, C1= 32.7. C,,H,,OCl, requires C1= 32.42 per cent . )

2 : 6-Dichlorothymol is a pale yellow oil, which is almost colour- less when freshly distilled, but gradually darkens on exposure to air and light. It is soluble in most organic solvents and in sodium or potassium hydroxides. It does not liberate iodine from potassium iodide. When 2 : 6-dichlorothymol was subjected to direct chlorination, hydrogen chloride was evolved, and 2 : 4 : 4-tri- chloro-3-methyl-6-isopropyl-A2 :%ycZohexadienone resulted.

2 : 6-Dichlorothymol Methyl Ether, C,,H,,Cl,*OMe.-This deriv- ative was prepared by warming 2 : 6-dichlorothymol with excess of methyl sulphate, destroying the excess of the latter with sodium carbonate, and pouring the resulting solution into water. The oil which separated was extracted with ether, and washed with dilute potassium hydroxide to remove traces of the unchanged phenol, and then with water. The solution was dried over sodium sulphate, and distilled under diminished pressure, when it passed over a t 129O/12 mm. :

0.1871 gave 0.2316 AgC1. C1=30*55.

This methyl derivative is a yellow oil very similar in appearance It is soluble in most organic solvents, but

C,,H,,OCl, requires C1= 30.47 per cent.

to 2 : 6-dichlorothymol. is insoluble in sodium hydroxide.

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CHLORINE ON THYMOL AND ON M-CRESOL. 545

2 : 4 : 4 : 5-TetrachZoro-3-methyl-6-~-chZorois~propyZ-h~ ;5-cycb hexadienone, C,,H90CI, (XIV).

This compound could be prepared only in small quantities by the chlorination, for several hours a t the ordinary temperature, of thymol in the presence of iodine, in dilute carbon tetrachloride or acetic acid solutions. The solvent was removed by evaporation, and from the residue, after it had remained for several days, there separated out a few crystals of the cyclohexadienone. The product was crystallised from light petroleum, methyl alcohol, or acetic acid, when it separated in white, flat needles, which melted at 95O:

0.1598 gave 0.3548 AgC1. C1= 54.93. CIoH,OC1, requires C1= 55.04 per cent.

This compound formed no acetyl or benzoyl derivatives, and was insoluble in sodium or potassium hydroxides, being slowly decom- posed by them on warming. On heating the substance in alcoholic solution i t liberated iodine from potassium iodide. The compound was decomposed with much charring by concentrated sulphuric acid at 150°, with the formation of tetrachloro-m-cresol, which separated as a solid from the hot acid.

C

2 : 4 : 6-Tric7~Zoro-m-cresoZ, C7H,0Gl, (IX). This substance was prepared by the chlorination, in the presence

of iron for about one t o two hours, of 3 - 4 grams of thymol in carbon tetrachloride solution. The solution was cooled in ice, and after evaporating off the solvent a white mass was obtained, which required to be recrystallised five or six times from dilute acetic acid or light petroleum before it was obtained pure. It can also be prepared by the chlorination for several hours of boiling m-cresol, and also by the chlorination of m-cresol in carbon tetrachloride solution. This last method yields by far the best product. Another method for its preparation is the action of concentrated sulphuric acid at looo on 2 : 4 : 4-trichloro-3-methyl-6-isopropyl-h2:5-cycZohexa- dienone. The substance, after several recrystallisations, melted a t 46O:

,

0.1924 gave 0.3921 AgC1. C1= 50.42. C,H,OCl, requires C1= 50.35 per cent.

2 : 4 : 6-Trichloro-m-crrsol is extremely soluble in all the ordinary organic solvents except light petroleum, it is sparingly soluble in boiling water, and readily so in sodium or potassium hydroxides. It has no action on potassium iodide, has a very penetrating odour, and is easily volatile in steam.

2 : 4 : 6-Tiicldoro-m-tolyl Methyl Ether, C7H4C1,*OMe.-This com-

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546 CROWTHER AND McCOMBIE: TEE ACTION OF

pound was prepared by warming trichlorclm-cresol with excess of methyl sulphate. The excess of the latter was removed with sodium carbonate, and the solid methyl derivative was separated and crgstallised from dilute acetic acid, when it separated in small, slender, white needles, which melted at 54-55O :

0.1974 gave 0.3792 AgCl. CT,H,OC'l, requires e l = 47.23 per cent.

A cetyl Derivative, C,H,Cl,*OAc.-This derivative was prepared by the action of acetic anhydride on trichloro-m-cresol in the praence of a drop of concentrated sulphuric acid. The mixture was poured into water, and the oil which separated was extracted with ether, washed with dilute potassium hydroxide and with water, and allowed to solidify in a vacuum desiccator. The crystals were separated and purified by a second extraction with ether, when they melted at 32O:

C1= 47.52.

0.2031 gave 0.3435 AgC1. C1= 41.84. C9H70,CI, requires Cl = 42-01 per cent.

2 : 4 : 5 : 6-TetrachZoro-m-cresol, C',H4OC1, (XIII).

This coqpound was obtained by the more or less prolonged chlorination of thymol in presence of iodine in a concentrated carbon tetrachloride solution. If iron were used as the catalyst, 3 grains of thymol were converted into tetrachloro-m-cresol after chlorination for two to three hours even in an ice-cold solution. The tetrachlorocresol separated out from a concentrated solution as a crystalline mass, and, a t this point, the chlorination was arrested as the tetrachlorocresol was very easily chlorinated further.

The best method, however, for the preparation of tetrachloro-ni- cresol consisla in treating 2 : 4 : 4 : 5 : 6-pentachloro-3-methyl-A~:6-cycZo- hexadienone (the final product of the chlorination of thymol or of rn-cresol) with excess of potassium iodide, the reaction being carried out in alcoholic or acetic acid solutions. The mixture is poured intc sodhm thiosulphate solution, and the yield is practically t h w r et ical .

As described previously, tetrachloro-m-cresol is also formed by treating 2 : 4 : 4 : 5-tetrachloro-3-methyl-6-~-chloroisopropyl-A2 : 5 - ~ y ~ l 0 - hexadienone wit*h sulphuric acid a t 150O.

When crystallised from light petroleum, acetic acid, or dilute alcohol, tetrachloro-m-cresol separates in slender, white, long needles, which melt at 189-190°:

0.1732 gave 0.4048 AgCl. C1=57*84.

2 : 4 : 5 : 6-Tetrachlol.o-m-cresoZ is soluble in most organic solvents, C7H40Cl, requires C1= 57-73 per cent.

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CHLORINE ON TRYMOL AND ON M-CRESOL. 547

and dissolves in potassium hydroxide, but is unattacked by warm concentrated sulphuric acid. It can be converted easily into acetyl and benzoyl derivatives, and, when treated with chlorine in carbon tetrachloride solution, it yields 2 : 4 : 4 : 5 : 6-pentachloro-3-methyl- A2 :5-cyclohexadienone.

A cetyl Derivative, C,H,Cl,*OAc.--This compound was prepared by the action of acetic anhydride on tetrachloro-m-cresol in the presence of a drop of sulphuric acid. On crystallisation from glacial acetic acid i t separated in flat needles, which melted at 117O :

C,H,02Cl, requires Cl= 49-30 per cent. 0.1955 gave 0.3877 AgC.1. C1= 49-07.

This compound is insoluble in cold alcohol, but is soluble in cold acetone or ether. It is readily hydrolysed by alcoholic potassium hydroxide.

Benzoyl Derivutiae, C7H3C1,*OBz.-This derivative was prepared in pyridine solution, and, when crystallised from glacial acetic acid or alcohol, melted a t 143-144O:

0.1998 gave 0.3278 AgC1. C1=40*59. C,,H,O,Cl, requires C1= 40.57 per cent.

2 : 4 : 4 : 5 : 6-Pentachloro-3-meth~l-A~~~-cycloh exadienone, C7H30Cl, (XV).

This campound was found to be the chief and final proauct of the complete chlorination of thymol in presence of either iodine or iron. The thymol was dissolved in a small quantity of carbon tetrachloxide, a little iron or iodine was added, and a stream of dry chlorine wils passed through the solution until the evolution of hydrogen chloride had ceased. I n the case of iodine as the catalyst, 5 grams of thymol required chlorination during two days a t 60° before the process was complete. With iron, however, the same quantity of thymol required only about four to five hours' chlorina- tion at the ordinary temperature. The pentachlorohexadienone, when crystallised from light petroleum, glacial acetic acid, or alcohol, separated in large, rhombic prisms with a slight yellowish- green tinge, which melted a t 92O:

0.1386 gave 0.3528 AgCl. el,= 62.96.

2 : 4 : 4 : 5 : 6-Pentachloro-3-methyl-A2~~-cyclol~exacEienone is readily soluble in acetone, benzene, toluene, chloroform, or ether in the cold, but it is insoluble in water. No acetyl or benzoyl derivatives of it could be obtained, and it is insoluble in alkalis. It jiberates iodine from potassium iodide in alcoholic or acetic acid solutions, and this reaction was followed quantitatively with the following

C7H30Cl, requires C1= 63-28 per cent.

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548 WATSON: THE CONSTITUENTS OF THE

result: 0.4650 gram of substance yielded 0.4215 gram of iodine. The equation C7H,0Cl, + 2KI = C,H,C140K + KCl + 1, requires 0.42 10 gram of iodine.

Concentrated sulphuric acid at looo oxidises the compound very readily to 2 : 4 : 5-trichlorotoluquinone, which separates from the hot acid as a yellow, crystalline mass.

2 : 4 : 5-Trichlorotolupuinone, C7H,02C13 (XVI).

This compound was obtained in small quantities, together with tetrachloro-m-crasol and 2 : 4 : 4 : 5 : 6-pentachloro-3-methyl-A2:5-cyclo- hexadienone, by the prolonged chlorination of thymol in the preEence of iodine or reduced iron. I n the presence of iodine the chlorination required about ten days, but with reduced iron small quantit ia of the toluquinone were obtained after chlorination for twelve hours.

The best method of preparation consists in treating 2 : 4 : 4 : 5 : 6- pentachloro- 3 - methyl - &2:5 - cyclohexadienone with concentrated sulphuric acid a t looo. After a few minutes a yellow, crystalline mass separates, and the reaction is found to be practically quantita- tive. The substance was recrystallised from a mixture of alcohol and benzene, and melted and decomposed a t 238O :

0.1769 gave 0.3368 AgGI. C1=47.10. C,H,O,C1, requires Cl = 47.23 per cent.

The identity of this substance was established by a mixed melting- point determination with a specimen of trichlorotoluquinone prepared by the oxidation of o-toluidine with sodium dichromate.

CHEMICAL DEPARTMENT, THE UNIVEI~SITY, EDUBASTON.

BIRMINGHAM.

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