4-ISOPROPYLDIHY DRORESORCIN. 675

LXXI .- Prepamtion and Prope&s o j 4 - h Prop$ dih y diaoresorcin.

By ARTHUR WILLIAM CROSSLEY.

AMONG the many interesting changes which substituted dihydro- resorcins undergo is one which they suffer on treatment with barium hydroxide. For example, Vorlander has shown (Anncclen, 1897, 294, 817 ; 1899, 308, 188) that when 4-phenyldihydroresorcin is boiled with barium hydroxide, hydrolysis takes place and the ring is broken with formation of P-phenyl-6-ketohexoic acid (P-phenyl-y-acetylbutyric acid),

C,R,=CH/ '\CH --f C6H,*CH

Exceptions are found to this reaction in the cases of 4 : 4-dimethyl- dihydroresorcin and 3 : 4 : 4-trimethyldihydroresorcin (compare Bey., 1897,30, 1801, and Trans., 1901, 79, 139),

CH,-CO CH,*CO

dH, .2$? . \CH,-C(OH)&.

neither of which substances behaves in the above-mentioned manner. The explanation is evidently to be sought in a difference of constitution, These two substituted dihydroresorcins differ in one point, and one point only, from those which have been found to hydrolyse on treat- ment with barium hydroxide : they contain two alkyl groups attached to the same carbon atom (marked with a +), whereas all those which have been found to undergo hydrolysis contain only one alkyl group in this position.

I n order to obtain further evidence on this point, 4-kopropyldihy- droresorcin has been prepared, and its behaviour towards barium bydroxide investigated.

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676 CROSSLEY : PREPARATION AND PROPERTIES OF

The starting point of the preparation was isobutylideneacetone, (CH,),CH*CH:CH*CO*CH,, prepared according to the directions of Pranke and Kohn (Moncbtd., 1899, 20, 876), and as this substance condenses with ethyl sodiomalonate to give‘ ethyl d-isopropyldihydro-

cH(co2Et)’co>CH, a characteristic re-

action of up-unsaturated ketone, it affords a further proof, if such were needed, of the formula assigned to this ketone by Franke and Kohn.

When the above ethyl salt is hydrolysed with either sodium car- bonate or potassium hydroxide, 4 - i s o ~ o p y Z d i ~ y d r o r e s o r c ~ ~ (formula I below) is obtained, which crystallines with 1H,O. Its constitution is proved by its method of formation, and also by the fact that on oxidation with sodium hypobromite it gives rise to P-isopropylglutaric acid (compare Trans., 1899,75,772 ; 1901,79, 139) :

When boiled with barium hydroxide solution, isopropyldihydro- resorcin is hydrolysed, as expected, with production of P-isopropyl-8- ketohexoic acid :

Apparently, then, it is the presence of two alkyl groups attached to one and the same carbon atom which differentiates between substituted dihydroresorcins hydrolysed by barium hydroxide and those which are not.

The ketonic nature of isopropylketohexoic acid was proved by the preparation from it of a semicarbazide and an oxime; and its constitution follows from the oxidation with dilute nitric acid, when it yields pimelic (isopropylsuccinic) acid,

whereas isopropyldihydroresorcin, under similar conditions, gives /%so propylglutaric acid.

The following comparison of the properties of isopropyldihydro- resorcin and isopropylketohexoic acid leaves no doubt as to the non- identity of the two substances :

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4-18OPBOPY LDIHYDBORESORCIN. 677

Oxidation product. FqCl, Water. B4. p. or

b. p. M. p. of

oxime.

I 1-1 I I- C,H,,O,,H,O,

Appreciably ni. p. 67.5".

soluble.

4'-WoPropyldihy d ro- isoPropylglutaric

iJoPropylsuccinic acid _.............. 145"

acid . . . ... ... . .. ... 93-94"

I n previous communications (Trans,, 1901, 79, 138 ; Proc., 1901, 17, 172), substituted dihydroresorcins have been called substitdted dihydroresorcinols or diketocyclohexanes ; but the author no longer re- tains these latter names, for although the substances behave apparently as diketones towards hydroxylamine, there can be no doubt tha t their most usual form is the ketoenolic constitution, represented by the following formula :

2

The positions of the various substituting groups are indicated by numbering the carbon atoms as above.

For these reasons, and also for brevity's sake, the name dihydro- resorcin will in future be adopted to designate this class of substances.

EXPERIMENTAL.

EtAyl 4-ko Propyldih ydaorssorcy late- 3,

Twenty-three grams of sodium were dissolved i n 275 C.C. of absolute alcohol, 170 grams of ethyl malonate added, and, after cooling, 112 grams of isobutylideneacetone (Franke and Kohn, Homxfsh., 1899, 20, 876). The mixture became reddish-pink and much heat was evolved. On shaking, the whole set to a faintly-yellow, semi-solid mass, which was heated on the water-bath for 4 hours to complete the reaction; water was then added, the alcohol evaporated, and the alkaline liquid extracted with ether, which treatment removes some unaltered material. After acidification with dilute sulphuric acid, the whole was again extracted with ether, the ethereal solution washed with water, dried over calcium chloride, and the ether evaporated, when 230 grams of a thick, yellow liquid were obtained, which, on standing, became semi-solid. The mass was spread on porous earthenware, thus giving 100 grams of a white solid, and on extracting the porous plate with ether, 98 grams of a thick, yellow liquid were obtained, which

VOL. LXXXI. z z

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678 CROSSLEY: PREPARATION AND PROPERTIES OF

showed no signs of crystallisation after many months' standing, and is at present being more fully investigated.

The white solid was purified by crystallisation from a mixture of benzene and light petroleum, and analysed :

0.1107 gave 0.2512 GO, and 0.0804 H,O,

Ethyl isopropyldihy droresorcylate dissolves slightly in water and readily in the ordinary organic solvents. It crystallises from the above-mentioned mixture in stellar aggregates of small needles melting at 100*5-101°. I t s aqueous solution gives a deep violet colour with ferric chloride solution.

C = 63.37 ; H = 8.07. CI,H,,04 requires C = 63.71 ; H = 7.96 per cent.

Ethyl isopropyldihydroresorcylate was hydrolysed by boiling for 2 hours with an equal weight of pure caustic potash dissolved in alcohol. (Hydrolysis may also be effected by boiling for about 15 hours with sodium carbonate solution.) Water was then added, the alcohol evaporated, and, after acidification with sulphuric acid, the whole extracted with ether and the ether evaporated. As this sub- stituted dihydroresorcin crystallises with 1H,O, it is of advantage not to dry the ethereal solution before evaporation. The solid rwidue, obtained in nearly theoretical yield, was purified by crys tallisation from dilute methyl alcohol and analysed :

0.1446 gave 0.3315 CO, and 0.1214 H20. C,H,,O,,H,O requires C = 62.79 ; H = 9.30 per cent.

isoPropyldihydroresorcin is sparingly soluble in water or light petroleum, but readily so in the ordinary organic solvents; its aqueous solution is intensely acid towards litmus paper and gives a deep purple colour with ferric chloride. It crystallises from dilute methyl alcohol, with 1H,O, in stout, flattened needles melting a t 6 7 * 5 O . When dried in a vacuum over sulphuric acid :

C = 62-52 ; H = 9.33.

0.8860 lost 0.0940 H,O. H,O = 10.61. C9H,,0,,H,0 requires H,O = 10.46 per cent.

The dried substance, when heated in a capillary tube, melts at 83O, and at about 100' a red film is formed above the substance, a phen- omenon noticed in the case of 4 : 4-dimethyldihydroresorcin (Trans., 1899, 75, 773). On analysis of the dried substance, the following numbers were obtained :

0.1197 gave 0.3073 CO, and 0.0980 H,O, C = 70.01 ; H = 9.10. CgH,,O, requires C = 70.13 ; H = 9-09 per cent.

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4-ISOPROPY LDIHYDRORESORCIN. 679

The silver salt, C,H,,O,Ag, prepared in the usual manner, is a white, insoluble precipitate :

0,1761 gave 0.0727 Ag. C,H,,02Ag requires Ag = 41 *38 per cent.

The dioxime was obtained by adding the calculated quantities of hydroxylamine hydrochloride and sodium hydroxide dissolved in the smallest possible quantity of water to an alcoholic solution of the ketone. On standing, the solution became violet, and gradually deposited crystals, which were separated, purified by crystallisation from dilute methyl alcohol, and the nitrogen estimated :

0,1186 gave 15.6 C.C. moist nitrogen a t 16'and 764 mm. N=15.41. C,H,,O,N, requires N = 15-22 per cent.

The dioxime is insoluble in benzene or chloroform, but readily soluble in methyl or ethyl alcohol on warming, and crystallises from dilute methyl alcohol in clusters of stumpy needles. I t s melting point is indefinite. On heating in a capillary tube, it runs together a t 1 4 5 O , forming a nearly clear jelly, which sticks to the side of the tube. On more strongly heating, it becomes cloudy, and a t 165O

Ag- 41.28.

decomposes and gives off gas. CH - co The ethyl ether, C,H7*CH<CH~.C(oc )>CH, prepared by heat-

2 5 ing the dry silver salt with ethyl iodide in dry ethereal solution, is a clear, faintly yellow, oily liquid boiling at 2S4O a t 762 mm. :

0.1204 gave 0.3190 CO, and 0.1086 H,O. ClIH1802 requires C = 72-52 ; H -- 9*89 per cent,

When hydrolysed with alcoholic potassium hydroxida, it is quan-

C = 72.26 ; H = 10.02.

titatively reconverted into isopropyldihydroresorcin. 1 -Bromo-4-isopropyZdihydroresorc~n, (CH,),CH* OH<CH:. CH --GO C(oH)>CBr,

was prepared by adding a solution of bromine in chloroform to one of dried isopropyldihydroresorcin (m. p. 82') in chloroform until the colour of the former just remained permanent, when hydrogen bromide was evolved and a heavy oil separated; which soon solidified. This was filtered off, purified by crystallisation from dilute alcohol, and the bromine determined :

0-2076 gave 0.1692 AgBr. C,H,,O,Br requires Br = 34.33 per cent.

Bromoisopropyldihgdroresorcin is insoluble in water, readily soluble in alcohol, acetone, or ethyl acetate on warming, and crystallises in nacreous scales. Its melting point depends on the rate at which it is heated; when heated in the ordinary way, it melts sharply at 169' to a deep red liquid, which at once decomposes and gives off

Br = 34.68.

2 2 2

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680 CROSSLEY: PREPARATION AND PROPERTIES OF

gas. Other determinations in which the substance was heated more and more slowly gave 166', 162', and finally as low as 152'. In each case, the substance melted sharply at the given temperature with de- composition and evolution of gas.

Oxidution of 4-isoYropyldihydroresorcin.

I. With Potassium Hypobromitd.-Thirty-four grams of bromine were poured into 400 C.C. of water cooled to 0' and a strong solution of sodium hydroxide slowly added until the colour of the bromine had disappeared. A solution of 7 grams of isopropyldihydroresorcin in sodium hydroxide (10 grams NaOH in 50 C.C. of water) was then poured in and the whole allowed to stand 4 hours. The solution, after separation from bromoforrn and carbon tetrabromide, was acidi- fied with hydrochloric acid, evaporated to about one-fourth of its original bulk, and repeatedly extracted with ether. The ethereal solu- tion, after drying over calcium chloride and evaporation of the ether, yielded 5 grams of a white solid, which proved to be P-isopropylglu- taric acid (compare Howles, Thorpe, and Udall, Trans., 1900,77, 942). Thus, it crystallised from water in stout needles melting a t 100-100a50, and gave a crystalline anilic acid melting a t 121'. On analysis of the acid, the following numbers were obtained :

0,1422 gave 0.2861 CO, and 0.1028 H20. C,H1,O, requires C = 55.17 ; H = 8.04 per cent.

11. With Nitric Acid.-Two grams of isopropyldihydroresorcin were heated to boiling with 20 C.C. of dilute nitric acid (I : l), when after a few moments oxidation took place vigorously. The whole was evap- orated on the water-bath, with repeated addition of water, when 1.7 grams of a white solid were obtained melting at 100' and giving an anilic acid melting a t 121', thus proving i t to be P-isopropylglutaric acid.

C = 54-87 ; H = 8.03.

P-isoPropyZ-6-ketohexoic Acid, CH3*CO*CH,*CH(C3H7)*CH2*C02H. isoPropyldihydroresorcin (1 part) was heated with barium hydr-

oxide (4 parts) and water (20 parts) for 36 hours in a flask attached to a reflex condenser. The whole was then evaporated to about one- third of its original volume, acidified with hydrochloric acid, and ex- tracted with ether. The ethereal solution, after drying over calcium chloride, was evaporated and the residual liquid purified by repeated distillation in a vacuum, and analysed :

0.1206 gave 0.2776 GO, and 0.1014 H,O.

isoPropylketohexoic acid is a perfectly colourless, thick liquid with

C = 62.77 ; H = 9.34. C9H1,03 requires C = 62.79 ; H = 9.30 per cent.

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4-ISOPROPY LDIHYDRORESORCIN. 681

a sharp, but not unpleasant odour. It boils a t 187' under 15 mm. pressure, and requires to be distilled as rapidly as possible, for on slow distillation, especially in air, it decomposes. The silver salt, C,H,,O,Ag, prepared in the usual way, is a white, insoluble pre- cipitate :

0.2184 gave 0.0852 Ag. C,H,,O,Ag requires Ag = 38.71 per cent.

The semicarbaxide, C,,H,,O,N,, was obtained by adding to an alcoholic solution of the ketonic acid the calculated quantities of semi- carbazide hydrochloride and sodium acetate dissolved in the smallest possible quantities of water and allowing the alcohol to evaporate slowly. The solid which separated crystallised from dilute alcohol in small, transparent plates melting at 144' with slow evolution of gas :

0.1146 gave 18.4 C.C. moist nitrogen at 18' and 756 mm. N = 18.44. C,,H,,O,N, requires N = 18.34 per cent.

0xime.-Five grams of hydroxylamine hydrochloride and 3 grams of sodium hydroxide dissolved in the smallest possible amount of water were added to an alcoholic solution of 5 grams of the ketonic acid and the solution heated to boiling for 4 hours. The pasty mass left on evaporating the solvent was warmed with absolute alcohol, filtered from sodium chloride, and the alcohol again evaporated. On stirring the residue with a few drops of very dilute acetic acid, it gradually solidified. It was spread on a porous plate, purified by crystallisation from ethyl acetate, and the nitrogen determined :

N = 7.45.

Ag = 39.01.

0.2064 gave 13.5 C.C. moist nitrogen at 19-5Oand 755 mm. C,H170,N requires N = 7.49 per cent.

The oxime crystallises slowly in stellar aggregates of compact needles melting a t 93-94'. It is practically insoluble in light petroleum, but ready soluble in the ordinary organic solvents, especially on warming.

Oxidation of Acetylisopropylbutyric Acid.--8.5 grams of the ketonic acid were heated with 90 C.C. of nitric acid (sp. gr. 1-15> for half an hour in a flask attached to a reflux condenser. The oxidation is not a very violent one. After adding water and evaporating off the nitric acid, 6 grams (calc., 7.3 grams) of a white solid were obtained, which crystallised from water in stout, transparent needles melting at 115- 11 6O. This is the melting point of pimelic (isopropylsuccinic) acid (compare Trans., 1898, 73, 22). To prove further the identity of this acid, a, portion was converted into the silver salt, and ans1,ysed :

0.2598 gave 0.1498 Ag. Ag=57*66. C,H,,0,Ag2 requires Ag = 57.75 per cent.

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682 INXES: THE INFLUENCE OF TEMPERATURE ON

The acid also gave an anhydride boiling at 255' at ordinary atmw spheric pressure, and from this an aiailic acid crystallising from dilute alcohol in shining scales melting at 135'.

As isol3ropybucci~ani~ic acid does not appear to have been previously described, a specimen was made for comparison, The pimelic acid employed was obtained by the fusion of camphoric acid with pot- assium hydroxide (Trans., 1898, 73, 22). It mas first converted into the anhydride boiling at 255' under ordinary atmospheric yres- sure, and this, on treatment with aniline in benzene solution, gave the anilic acid, crystallising from dilute alcohol in beautiful, nacreous scales melting at 135'. It is fairly soluble in benzene and chloro- form on warming, and readily so in ether, ethyl acetate, acetone, or alcohol in the cold :

0.3006 gave 15.4 C.C. moist nitrogen a t 20' and 766 mm. N = 5.91. C,,H,?O,N requires N = 5.95 per cent.

The author's thanks are due to the Research Fund Committee of the Chemical Society for a grant defraying the cost of the materials used in this investigation.

CHEMICAL LABORATORY, ST. THOMAS'S HOSPITAL.

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