144 RIPPING AND HILL : a-KETOTETRAH'YDRONAPH!FHALENE. XVII.-a-Ketotetrah ydronaphthalene. By FREDERIC STANLEY KIPPING, Ph.D., D.Sc., F.R.S., and ALFRED HILL. THE conversion of phenylpropionic chloride into a-hydrindone by the action of aluminium chloride under the conditions described by one of us in a previous communication (Kipping, Trans., 1894, 65, 680) is an example of intramolecular condensation by which an open- is converted into a closed-carbon chain ; the reaction also provides by far the most convenient method yet known for the preparation of a-hydrindone, as, with due care, the yield is invariably very good, and phenylpropionic chloride itself can be obtained without any difficulty in almost unlimited quantity; this method of preparation was, there- fore, made use of i n later investigations of the derivatives of a-hydrin- done (Kipping and Revis, Trans., 1897, 71, 238).KIPPINO AND HILL : d-KETOT~RAETPDRONAPHTEALENE. 146 That such a reaction would be capable of more general application WW, of course, extremely probable, but until quite recently no oppor- tunity offered itself of putting this view to the test of experiment ; now, however, the reaction is being tried with various substances, and in the present paper some of the first results of this work are described.Taking the well-known synthesis of a-naphthol from phenyl-py- crotonic acid by Fittig and Erdmann as an indication of the ease with which intramolecular condensation may occur in the case of a benzene derivative containing a suitable unsaturated side chain, it seemed very probable that a similar change might be brought about in the case of phenylbutyric acid, if the chloride of this acid were treated with aluminium chloride in a suitable manner ; if so, the analogy between phenylpropionic and phenylbutyric acid would be complete, the one giving a-hydrindone, the other a-ke tot e t rah y dronaph thalene.')'';H2 + HCl I " j C H 2 - 1,) /"TiH2 )CH, - COG1 co Experiments showed that a-ketotetrahydronaphthalene is, in fact, formed by the action of aluminium chloride on phenylbutyric chloride under the conditions described below, but, so far, satisfactory yields have not been obtained, owing probably to the readiness with which the ketone, when once formed, undergoes further condensation of the ordinary type ; a sufficient quantity of this substance, however, has been obtained t o enable us to study its properties in some measure, and to prepare from it various crystalline derivatives. a-Ketotetrahydronaphthalene is isomeric with, and closely related to, the P-keto-compound, which was first prepared by Bamberger and Lodter (Ber., 1893, !B, 1833) by the action of alkalis on " tetrahydro- naphthylene chlorhydrin '' (2 :, 3-~hlorhydroxytetrahydronaphthalene), and afterwards examined by Bamberger and Voss (Bey., 1894, 2'7, 1547).As far as can be judged, the two compounds resemble one another very closely in properties, and both show the ordinary general reactions of ketones ; the semicarbazone, oxime, hydrazone, and para- bromhydrazone of the a-keto-compound are described in this paper, the oxime and hydrazone of the P-ketone having been previously prepared by Bamberger and Voss (Zoc.cit.). That the substance we describe as a-ketotetrahydronaphthalene really has this constitution is shown, not only by its method of formation and ketonic properties, but also by the fact that it can be indirectly converted into a base which seoms to be identical with ac-tetrahydro- Phenylbutyric chloride, a- Ketotetrahydronaphthalene.146 KIPPING AND HILL : a-KETOTETRAHYDRONAPHTHALENE. a-naphthylamine; this base was first obtained by Bamberger and Bammann (Ber., 1889, 22, 951) by reducing tetrahydro-1 : 5-naphthyl- enediamine with sodium and amylic alcohol, and then eliminating the amido-group combined with the unrecluced aromatic nucleus. NH, CII, CH, CH, \/\/ \/\/ /\/'\C€€.> - /\/\C€€., /\/\cH, I I 'UH, I I ICH, CO I 1 iCHi CH-NH, \/\/ CH-NH, 1 : 5-Tetrah~dro1rapI1tbyl- Tetraliydro-a iiaphthyl- a-Iietotetrahyclro- eiiediamiiie. smine.naphthalene. The conversion of a-ketotetrahydronaphthalene into this base was accomplished by first preparing the oxime, and then reducing the latter with sodium amalgam in acetic acid solution. The study of this interesting ketone is being continued. A portion of the expense incurred in this and in two earlier inves- tigations of a similar kind (Kipping, Trans., 1894, 65, 6SO; Kipping and Revis, Trans., 1897, '71, 338) has keen met by a grant kindly awarded by the Government Grant Committee of the Royal Society. Ex P E R I 31 EN TA L. P~epcwc~tion of Phen?/Zbut?/~*ic Acid-The preparation of a large quantity of phenylbutyric acid by the method which we employed is not a very easy task, but we were unable to find any process which appeared to be more suitzlble, recorded in the literature.Starting with benzaldehyde, anhydrous sodium succinate, and acetic anhydride, me first prepared the mixture of phenyl-py-crotonic and phenylparaconic acids under the conditions laid down by J a p e (AnnoZen, 1883, 216, 97), but instead of then separating these two compounds by dissolving out the phenyl-py-crotonic acid with carbon bisulphide, we submitted the dried mixture directly to dry distillation under reduced pressure (about 30 mm.), whereby, as J a p e has already shown (Zoc. cit.), the phenylpsrsconic acid is decomposed into phenyl-/3y-crotonic acid and carbonic anhydride, a small quantity of phenylbutyrolactone being also formed from the phenyl-py-crotonic acid by an intramolecular change.The distillate, which solidifies on cooling to a brown, pasty, crystalline mass, was spread on porous earthenware to separate the phenylbutyrolactone and other oily impurities, and afterwards recrystallised from hot carbon bisulpliide, froin which the phenyl-py-crotonic acid was deposited in almost colourless needles; the last portions of this acid generally contain a little benzoic acid, this compound being always present in the original condensation product in large quantities; it is bestKIPPINU AND HILL : a-ICETOTETRAHYDRONAPHTHALENE. 147 removed by heating the mixture on a water-bath, the residue being again crystallised from carbon bisulphide. The phenyl-py-crotonic acid was thus obtained in colourless needles melting sharply at 86', but the yield was always very poor, owing to the formation of tarry matter in the original condensation process.For the conversion of this unsaturated compound into phenylbutyric acid, the pure acid was reduced with sodium amalgam in alkaline solution, and after precipitating with hydrochloric acid and filtering, the rest of the product was extracted with ether, and the whole purified by recrystallisation from this solvent ; the acid then melted at 47-48O as stated by J a p e (Zoc. cit.). We did not experience any difficulty in reducing the phenyl-By-crotonic acid at ordinary tempera- tures, although, according to Jayne, prolonged treatment and warming are necessary.Phenpllbutyric chloride, C,H,~CH2*CH,*CH,*COCI, is easily prepared by treating the dry, powdered acid with a slight excess of the theoreti- cal quantity of phosphorus pentachloride at ordinary temperatures, a vigorous action immediately setting in ; instead of separating the product from the phosphorus oxychloride by fractional distillation under reduced pressure, as in the case of phenylpropionic chloride (Trans., lS91,65,484), we merely heated the oil on a water-bath under diminished pressure until the oxychloride had volatilised, using the residual phenylbutyric chloride, which is sufficiently free from impurity, for the subsequent experiments. Phenylbutyric chloride, as thus obtained, is a yellowish, mobile liquid, having a slight, but not very unpleasant, odour ; when poured into water, it rapidly solidifies to crystals, which are only very slowly decomposed by cold water, and which do not immediately dissolve in a cold dilute solution of sodium carbonate.Actioib of Alunzinium Chloride on Plmplbutyric Chloride. Experiments were made in order to ascertain the conditions under which the conversion of phenylbutyric chloride into a-ketotetrahydro- naphthalene could be accomplished, and we commenced by employing very much the same method as in the case of a-hydrindone, the acid chloride, mixed with about four times its weight of light petroleum (b. p. 40-60°), being treated with its own weight of anhydrous alu- minium chloride. Under these conditions, however, only a very slight reaction, if any, occurred, and even after heating on the water- bath during 30-40 minutes, the phenylbutyric chloride was found t o be unchanged ; on employing as diluent a sample of light petroleum boiling at 60-80°, the reaction was almost as sluggish as before, but with petroleum boiling at 100-110' a vigorous evolution of hydrogen148 KIPPING AND HILL : a-KETOTETRAHYDRONAPHTHALENE. chloride set in on heating, and in a short time the reaction abruptly ceased.An examination of the product from this last experiment showed that the yield of ketone was extremely small, most of the acid chloride having been converted into a pale brown resin. For this reason, a smaller proportion of aluminium chloride was employed in the later experiments, and the results appeared to be distinctly better.The most satisfactory yield, so far, has been obtained by working in the following manner. Phenylbutyric chloride (5 parts) is dissolved in light petroleum (25 parts) boiling at 100-1 lo”, aluminium chloride (4 parts) is added, and the mixture is rapidly heated on a boiling water bath in a flask provided with reflux condenser ; after a very short time, hydrogen chloride is very rapidly evolved, and during this reaction the flask is repeatedly and vigorously shaken. At the end of about 10 minutes, or when the evolution of gas suddenly ceases, the contents of the flask are cooled and water carefully added; finally, the mixture is submitted to distillation in steam. The petroleum which passes over first contains only a smallquantity of the ketone, the rest distilling over slowly with the steam and leaving in the flask a brown, oily, non-volatile substance, which, on cooling, solidifies to a brittle resin; the ketone is isolated bp evaporating the petroleum and by extracting the aqueous portion of the distillate with ether.The a-ketotetrahydronaphthalene obtained in this way as a pale yellow oil is probably slightly impure, and is further treated in the manner described below ; the yield is by no means satisfactory, being at t h s most only about 10 per cent. of the theoretical, but it is probable that, as in the case of a-hydrindone, further experiments will lead to the discovery of some slight modification of the process which will give much better results. The principal product of the reaction is the brown, brittle resin, referred to above ; this substance is probably formed from a-ketotetra- hydronaphthalene by a condensation process similar t o that which occurs in the case of “anhydrobishydrindone,” or by the further action of phenylbutyric chloride on the ketone in presence of aluminium chloride. To obtain some information on this point, some of the resinous substance was oxidised with nitric acid, and it wag found to be ultimately converted into phthalic acid; this fact Heems to justify the above assumptions, and to indicate that if this secondary reaction could be prevented the yield of the ketone would be as good as in the case of a-hydrindone.Wheu working with small quantities of a-ketotetrahydronaphthalene, the best method of purification is doubtless the following, The crudeKIPPING AND HILL : a-KETOTETRBHYDRONAPHTHALENE. 149 oil is converted into its sparingly soluble semicarbazone in the manner described later, and after recrystallisation it is heated in a small Wurtz flask with rather more moderately-concentrated hydrochloric acid than is required t o combine with the semicarbazide; the semi- carbazone is thus decomposed with regeneration of the ketone, which can be distilled off in a current of steam and extracted with ether.The addition of a little acetic acid, in which the semicarbazone is readily soluble, hastecs the reaction. In this operation, there is no appreciable charring if the pure semicarbazone be employed, and the decomposition appears to be normal, as expressed by the following equation, C1,H,,:N*NH*CO*NH, + H20 = C,,H,,O + NH,*NH*CO*NH,.a-Ketotetrahydronaphthalene is a colourless, mobile, highly refrac- tive liquid. It does not crystallise when kept for some days at ordinary temperatures, or when cooled to Oo, whereas the correspond- ing @ketone solidifies when cooled, and melts again at 1 8 O (Bamberger and Voss, Zoc. cit.); il; does not seem probable that this difference in behaviour is due to the presence of impurity in the a-ketone, as the process just given appears to be a very satisfactory method of purifi- cation. a-Ketotetrahydronaphthalene is specifically heavier than water at 15*, and is moderately easily volatile in steam. It has only a faint odour, recalling that of camphor, but when warmed it has 5t distinct odoiir of peppermint.It shows many of the ordinary reactions of a ketone, and yields crystalline products with hydroxylamine, phenyl hydrazine, kc.; it does not appear to dissolve in, or to combine with, sodium hydrogen sulphite in aqueous solution, although the P-ketone forms a crystalline additive product with this reagent, The ketone itself mas not snalysed, as its composition is established by its method of formation and properties, and by the analysis of the semicarbazone. When the crude ketone, obtained by the method described above, is heated with semicarbazide hydrochloride and sodium acetate in aqueous alcoholic solution, the separation of an almost colourless, crystalline compound soon commences, and the reaction is completed by warming on the water-bath during about 2 hours; the hot solution is then diluted with water, allowed to cool, and the product separated by filtration, and washed well with cold water.When purified by recrystallisation from hot alcohol and dried over sulphuric acid, i t gave the following result.150 KIPPINCI AND HILL : a-ICETOTETRABYDRONAPHTEALENE. 0.1640 gave 0.3885 GO, and 0.0968 H,O. C = 64.6 ; H = 6.6. CllH13N,0 requires c' = 65.0 ; H = 6.4 per cent. a-Ketotetrahydronaphthalene semicarbazone crystallises from alcohol in long, transparent needles or prisms, usually forming aggregates of a rosette-like form ; these crystals are distinctly yellow, their colour being almost as intense as that of quinone, but when in a fine state of division the substance appears almost colourless.The melting point is not very definite, for when heated moderately quickly the finely-divided sub- stance melts at about 217', but larger crystals only sinter at this temperature, and do not liquefy completely until about 2209 when effervescence sets in and the substance darkens slightly ; on heating more strongly, a large quantity of gas is disengaged and a yellow liquid remains. The semicarbazone is comparatively sparingly soluble in boiling chloroform and ethylic acetate, and apparently insoluble in water ; it dissolves fairly easily in boiling alcohol and boiling acetone, and also in warm acetic acid, but i t seems to be decomposed on boiling its acetic acid solution. As stated above, this compound may be con- veniently employed in the purification of the ketone, as the latter is immediately regenerated on warming the semicarbazone with hydro- chloric acid ; it also affords the best means of detecting and identifying the ketone, the phenylhydrazone being far less suitable for such purposes.a - K e t o t e t r a j ~ ~ d ~ o ~ ~ a i ~ ~ t j ~ ~ ~ n ~ Pilenp?hpdvaxone, C,,€€,,:N*NHPh. This compound is easily obtained by treating the purified ketone with phenylhydrazine acetate in dilute acetic acid solution in the usual manner, combination taking place spontaneously ; after warm- ing gently, water is added, and the product, which is precipitated as a thick, yellow oil, is washed well with cold water, and then dissolved in methylic alcohol. From this solution, the hgdrazone separates, on spontaneous evaporation, in a crystalline condition, but if the warm solution be rapidly cooled, the compound is generally deposited as an oil.The crystals obtained from methylic alcohol and other solvents are massive, transparent, almost colourless six-sided and rhomboidal plates melting a t 84-85', a t the same time effervescing and decom- posing; they are readily soluble in most of the ordinary organic solvents, and dissolve comparatively easily even in boiling light pet- roleum, separating again, on cooling, in lustrous, transparent prisms, The hydrazone is very unstable, and soon decomposes on exposure to light and air ; its behaviour towards hydrochloric acid seems to be similar to that of the parabromo-derivative described below.KLPPINO AND HILL : a-KETOTETRAHYDRONAPHTHALENE. 151 a- Ke t ote t mlbgdronaph t Acc Zene Pccrccbromophe n9II~3drcczo12e, C,,H,,:N*NH* C6H,Br.The preparation of this substance from the purified ketone and parabromophenylhydrazine is carried out exactly as described in the case of the preceding compound, interaction taking place very readily ; the almost colourless, oily product, which is precipitated on the addi- tion of water, crystallises immediately when treated with a little methylic alcohol, and is easily purified with the aid of this solvent, from which i t separates, on cooling, in long, colourless prisms, or in massive, transparent crystals. It melts a t 117-llS", when heated fairly quickly from about 1 loo, effervescing and decomposing, and i t is readily soluble in cold ether, ethylic acetate, acetic acid, and benzene; i t also dissolves in boiling light petroleum, but, on cooling, separates again almost com- pletely in nodular aggregates of needles. It is more stable than the hydrazone, and does not change colour when exposed t o light and air during several days.Attempts to regenerate the ketone by distilling the parabrom- hydrazone with moderately concentrated hydrochloric acid were not successful ; under these conditions, the bromhydrszone is converted into a crystalline compound, which is probably produced by a change analogous to that which occiirs in the formation of '' benzyleneindol " from the phenylhydrazone of a-hydrindone (compare Hausmann, Be?*., 1889, 22, 2019 ; Kipping, Trans., 1894, 65, 494). a- h~etotetra~~ldront?btha Zeneoxime, C,,H,,: NOH. On gently heating a solution of the purified ketone in dilute methylic alcohol with hydroxylamine hydrochloride and excess of potash, the separation of a crystalline compound soon commences, if the alcohol be sufficiently dilute, and on allowing the solution to evaporate on the water-bath, most of the product is deposited in colourless plates.It is easily purified by recrystallisation from dilute methylic alcohol, the lustrous, transparent, well-defined rhomboidal crystals thus obtained generally exceeding 10 mm. in diameter. It melts at 102.5-103.5° without decomposing, and is very readily soluble in cold ether, chloroform, mcthylic alcohol, and most other solvents ; i t also dissolves freely in cold concentrated potash, but i t is insoluble, or nearly so, in water.152 KIPPING AND HILL : ~-KETOTETRAHYDRONAPHTHALENE.Convemion of a- Ket otetrahydronapht ha Zene into Tetrahydro-a- nuphth y lamine. Alhhough the method of formation of the ketone described above and the analysis of its semicarbazone left little room to doubt that it had the constitution assigned to it, we thought it would be inter- esting t o t r y and convert it into one of the tetraliydronaphthalene derivatives of known constitution ; for this purpose, experiments were made with the object of converting the oxime into the tetrahydro-a- naphthylamine described by Bamberger and Bammann (Ber., 1889, 22, 951). Attempts to reduce the oxime with sodium and moist &,her were not successful ; even after employing a large excess of sodium, a portion of the ethereal solution gave, on evaporation, crystals of the un- changed oxime, and a basic substance appeared not to have been formed ; we, therefore, tried the action of sodium amalgam in warm dilute acetic acid solution, and found that reduction took place very readily.After using the amalgam in considerable excess of the theoretical quantity, the acid solution was submitted to distillation with steam, but as no unchanged oxime passed over, the solution was rendered strongly alkaline with potash, and again submitted to steam distillation. A colourless, strongly basic oil, which was only moderately soluble in water, then collected in the receiver. This aqueous distillate, having been mixed with excess of hydrochloric acid and evaporated almost to dryness on the water-bath, left a consider- able quantity of a salt which crystallised in needles or prisms, and was very readily soluble in water ; the yield seemed to be practically theoretical. I n order t o prove that this salt was the hydrochloride of tetra- hydro-a-naphthylamine, a portion of it was roughly dried at looo, and then heated for a few minutes with excess of acetic anhydride; on subsequently cooling and adding water, the cccetyl derivative of the base separated in colourless needles. Bamberger aud Baminann (Zoc.cit.) describe this ace tyl derivative as crystallising from very dilute alcohol in felted masses of needles, and they give 148-149' as its melting point. The compound we obtained had these and all other properties mentioned by Bamberger and Bammann, except that it melted at 144-145', and its melting point underwent no change on recrystallisation.As, therefore, there was this considerable difference in melting point, which is diflicult to account for, further evidence as to the identity of our base was desirable. For this reason, we prepared the platinochloride, a salt which isPURDIE & PITKEATELY: PRODUCTION OF ACTIVE ACIDS, ETC. 153 immediately precipitated in yelIow plates or prisms on the addition of platinic chloride to a solution of the hydrochloride of the base. This compound crystallised from water in long, flat, orange-yellow prisms, was readily soluble in hot water and cold methylic alcohol, and melted immediately at 140' when suddenly heated, thus indicating that it contained water of crystallisation ; these properties agreed with those assigned to the platinochloride of tetrahydro-a-naphth ylamine by Bamberger and Bammann, and our salt, like theirs, melted at 190°, decomposing and effervescing; t h a temperature at which the salt melts and decomposes varies, however, within very wide limits, according to the rate of heating, and on heating quickly the tempera- ture can be raised to about 197' before liquefaction and decomposition ensue. An analysis was, therefore, necessary to confirm the supposed identity of the two compounds. 0.4543 salt, dried over sulphuric acid, lost 0.0232 at looo. H,O = 5.1. 0.4311 anhydrous salt gave 0.1224 platinum. Calculated for (C,oHl,N),,H2PtC16 + 2H,O, H,O = 4.87 per cent. Calculated for (C,oHl,N)2,H,PtC16, Pt = 27.6 per cent. On ignition, the salt gave off fumes having a strong odour of Pt = 28.4. naphthalene. UNIVERSITY COLLEGE, NOTT I N o IJ A M.