PERKIN ON THE ARTIFICIAL PRODUCTION OF COUMARIN. 53 VI.-On the Artaftcial Production of Cournaih and Formation oj* its Homologues. By W. H. PERKIN,F.R.S. IT is well known that coumarin when fused with hydrate of potassium yields salicylic and acetic acids. This fact has naturally led chemists to assume that there must exist a close relationship between this body and the salicylic series. No one however appears to have studied this subject and in fact when we consider the f'orrnula of coumarin and compare it with that of any member of that series we see that there is but little room for speculation; for example if we compare the formula of coumarin with that of the liydride of salicyl it will be seen that there exists only a difference of two equivalents of carbon but it must be remembered that salicylic acid does not result from the action of hydrate of potassium upon cournarin but is in fact a product of the decomposition of coumaric acid there- fore speaking correctly it is coumaric acid and not coumiirin which is related to the salicylic series.PERKIN ON THE ARTIFICIAL PRODUCTION Under the name of aceto-salicylol is described a body iso- meric with coumaric acid and this substance being an acetyl derivative of the hydride of salicyl should yield if fused with hydrate of potassium exactly the same products of decompo- sition as coumaric acid would if treated in a similar manrier. In a paper I lately had the honour of reading before this Society I mentioned that I was unable to obtain aceto-salicylol or more correctly the hydride of aceto-salicyl by the met.hod of Cahours and also that my endeavours to prepare it by the action of acetic anhydride upon the hydride of salicyl were unsuccessful.It then appeared to me probable that if the hydride of salicyl were replaced by its sodium derivative I might expect a better result thus,-Hydride of sodium-Hydride of aoeto-Salicyl. salicyl. On performing this experiment the following results were obtained. The hydride of sodium-salicyl when submitted to. the action of acetic anhydride rapidly loses its yellow colour and then dissolves; this change is attended with a very considerable ele- vation of temperature the mixture becoming quite hot. After this reaction has moderated the product when boiled for a few minutes and then poured into water sinks as an oil acetate of sodium dissolving.On distilling this oil any acetic anhydride that may have escaped decomposition comes over at first then hydride of salicyl ; the temperature then rises rather quickly and when it has reached 290° all the remaining product on being distilled into a separate receiver solidifies to a crystalline mass on cooling. This product when purified by pressure between bibulours paper aiid recrystallised two or three times from alcohol gave the following number on analysis :-I. -2396 of substance gave -6508 of CO and -0942 of H,O. 11. *2387of substance gave -6467 of CO and -0920 of H,O. OF COUMARIN AND FORMATION OF ITS HOMOLOGUES.55 These numbers give percentages agreeing with the formula -as the following comparisons will show :-Theory. Experiment. F A \ Y I. i . C ...... 108 73.97 74.07 73-81 H ...... 6 0 ...... 32- 4.11 21.92 4.36 - 4.28 - 146 10@00 It will be seen that this formula is not that of the hydiide of aceto-salicyl being deficient by an equivalent of water. It is however the formula of couma.rin. To prove that this substance is in reality pure coumarin and identical with the natural product the following comparisons of its properties with those of a specimen prepared from the Tonka bean were made. I. When crystallised from water side by side these two products could not be distinguished the one from the other the appearance of the crystals and their grouping being identica.1.11. Crystallised from alcohol side by side they appeared per- fectly alike. 111. Their melting points were also the same. IV. Their boiling points were also the same. V. When heated with strong aqueous hydrate of potassium each yielded coumaric acid and moreover the acid prepared from both specimens possessed the same melting point. VI. Fused wit,h hydrate of potassium they yielded salicylic acid. VII. They also possessed exactly the same odour. It will be remembered that some time since I made a verbal communication to the Society upon the artificial formation of this body,* but dated that I had not had an opportunity of ascertaining whether it was identical or only isomeric with the natural product ;from the foregoing comparisons however I think I may safely conclude that this artificial coumarin is the same as that obtained from the Tonka bean.It will not perhaps be out of place to make a few obser- @ Laboratory vol. i p. 136. PERKIN ON TEEE ARTIFICIAL PRODUOTION vations respecting the properties of coumaiin which I have found to differ somewhat from those described in chemical works. The melting point of this substance is nearly 20" higher than that recorded being between 67' and 67"-5C. Its boiling point is also much higher my experiments giving 290O.5 to 291OC. as the temperature whereas it is generally stated as 27OOC. It is also mentioned that cournarin is easily soluble in a solution of hydrate of potassium; this remark is perfectly true when applied to boiling but not to cold solutions of that alkali ; the slender crystals obtained by crystallising this sub- stance from water dissolving only with extreme slowness in a strong cold aqueous solution of hydrate of pota.ssium.The melting point of coumaric acid I have found to be between 207' and 208" C. 190' C. being the temperature usually given. The production of coumarin by means of acetic anhydride and the hydride of sodium-salicyl made it appear probable that if other anhydrides were substituted for the acetic a whole series of bodies homologous with coumarin might be pro-duced. This anticipation has been verified by experiment. Butyric Coumarin. Butyric anhydride acts but slowly upon the hydride of sodium- salicyl unless heat be applied the sodium compound then loses its colour and gradually dissolves; after boiling for a few minutes the product if poured into water separates as an oil the butyrate of sodium which has been formed dissolving.On rectifylng this oil butyiic anhydride and a little hydride of salicyl at first come over the temperature then rapidly increases and all the product distilling above 290" C. crystallises on cool-ing. This is rendered perfectly pure by pressure between bibulous paper and two or three crystallisations from a.lc0- hol. In one experiment I obtained three grammes of this substance &om twelve grammes of the hydride of sodium- aalicyl. When submitted to analysis it gave the following numbers :-I.-1976 of substance gave *5474 of CO and 01049of H,O. OF COUMARIN AND FORMATION OF ITS HOMOLOGUES. 57 11. -2125 of substance gave ,5902 of CO,and -1115of q0. These numbers give percentages agreeing with those required by the formula- C11H1002 as the following comparisons will show :-Theory. Experiment. I. 11. Cll.. .... 132 '75.86 75-55 75.74 Hlo .... 10 5-75 5.89 5.82 0 ...... 32 18.39 - - 174 100*00 The formula of this substance is C,H higher than that of coumarin the difference being the same as that existing be- tween acetic and butyric acids; this body is in fact a butyric counntarin homologous with the natural product. Butyric coumarin melts at from 70" to 71" C. and on cooling solidifies to a beautifid crystalline mass; at 296' to 297' C.it distils with slight decomposition. It is but little soluble in boiling water the solution becoming milky as it cools and after a time depositing a small quantity of crystals in the form of minute needles. In boiling alcohol it dissolves fieely and on standing separates fiom this solvent in large semi-opaque prisms. It is easily soluble in ether. This body possesses the odour of ordinary coumarin and also of fiesh honey. Butyric coumarin is nearly insoluble in cold aqueous hydrate of potassium and even when gently heated with a saturated solution of that alkali it only melts and floats as an oil upon its surface; if more strongly heated however it dissolves per- fectly forming a pale yellow solution; thk on being further concentrated becomes opaque and on standing a few moments an oily fluid rises to the surface which upon cooling changes to a tenacious mass; it can then easily be separated from the excess of hydrate of potassium which remains fluid.This sub- stance is a compound of butyric coumarin and hydrate of potas- sium ; it is deliquescent and very soluble in water; acids PERKIN ON THE ARTIFICIAL PRODUCTION easily decompose it with separation of butyric coumarh. When heated this compound dries up to a yellow amorphous mass and then undergoes decomposition being converted into the potassium salt of a new acid apparently homologous with coumaric acid; in fact the coumaric acid of butyric coumaiin.This acid is crystalline and easily soluble in carbonate of sodium and ammonia. For want of sufficient substance I have not been able to analyse this acid. The addition of bromine to this coizrnarh causes it to liquefy and on distilling the product a tough resinous mass is obtained giving when digested with alcoholic hydrate of potassium an acid which may be separated from the alkaline solution by means of hydrochloric acid. Ordinary coumarin when treated with bromine yields a similar product. Butyric coumarin when heated with fused hydrate of potas-sium decomposes yielding salicylic acid together with hydrate of phenyl and apparently butyric acid; but the odour of this latter compound is much masked by the presence of the hydrate of phenyl.Ckleric Cournarin. The hydride of sodium-salicyl appears to be scarcely affected by valeric anhydride in the cold but upon the application of heat thege two substances gradually react upon each other forming a clear liquid. In performing this experiment I prefer to add the sodium compound to the boiling anhydride and then to digest the mixture for a few minutes. The oily pro-duct of this reaction after being agitated with water to remove valerate of sodium is collected and distilled the portion boiling above 290"C. being kept separate. This distillate unlike those obtained in the preceding experiments does not crystallise even after standing for days and it was only by repeated trials that I succeeded in obtaining a method for its purifica- tion.This process is based upon the'propcrty of coumarins to dis solve in boiling solutions of hydrate of potassium and was carried out in the following manner :-The above oily distillate after being well agitated with a strong boiling solution of hydrate of potassium was diluted with OF COUMARIN AND FORMATION OF ITS HOMOLOGUES. 59 water and then mixed with ether to separate all oily products the clear aqueous solution when acidified with hydrochloric acid liberated the new coumarin which was taken up with ether and the ethereal solution agitated with carbonate of sodium to remove any acids that might be present. On evaporating this solution the new prodiict was obtained as an oil solidify- ing to a crystalline mass upon cooling. It wa.s then separated from oily impurities by pressure between bibulous paper ; two or three crystallisations from alcohol then rendered it perfectly pure.From twelve grammes of the hydride of sodium-salicyl and about 14 grammes of valeric anhydride I have obtained by the above method two grarnmes of this new coumarin. Two combustions of separate preparations of this body gave the following numbers :-I. ,1990 of substance gave -5600 of C02and *1153of H,O. 11. *2725of substance gave 07630of CO and -1610 of H,O. These numbers give percentages agreeing with the formula- as the following comparisons will show Theory. Experiment. I. 11 C12 144 76.59 7 6.74 76-36 6-43 6.36 HI2 12 6.38 32 17 *03 A -02 -a. -L. 188 100.00 This substance is therefore aaleric cournarin.Valeric coumarin melts at 54O C. and on cooling solidifies to a splendid crystalline mass; at 301"C. it boils a.nd distils with slight decomposition. It possesses a coumaric odour but not to the same extent as the butyiic coumarin. In boiling water it dissolves to a small extent but i8 apparently iiisoluble in cold water. It is very soluble in alcohol fiom which it crystal- lises in splendid transparent prisms nearly three-quarters of an PERKIN ON THE ARTIFICIAL PRODUCTION inch in length; they appear to be oblique six-sided prisms. This body is also very soluble in ether. This coumarin appears to be insoluble in cold solutions of the alkalies. If added to a concentrated solution of hydrate of potassium diluted with about a fourth of its volume of water and gently heated it melts and floats as an oil but when heated fwther perfectly dissolves.This solution on being concen-trated becomes milky and after standing a few moments an oily layer forms onits surface becoming a tenacious mass upon cooling; this is a compound of valeric coumarin and hydrate of potassium. This product is very deliquescent and easily soluble in water. Hydrochloric acid decomposes it liberating the valeric coumarin. If heated strongly it decomposeR yield- ing an acid most probably valeric coumaric. With fused hydrate of potassium this coumarin yields salicylic acid hydrate of phenyl and apparently a small quantity of valeric acid. When distilled with pentachloride of phosphorous it yields a viscid oil which if gently heated emits a turpentinic odour and when burnt communicates a green colour to the edges of the flame showing it to be a chloiinated body.From the preceding results we see that coumarig is but a member of a whole series of homologous bodies producible from the hydride of sodium-salicyl by means of anhydrides. The question therefore which presents itself for consideration is what is the nature of the reaction by which these bodies are formed and their consequent constitution 8 In this inquiry it will be well to consider the formation of ordinary coumarin as the history of this substance is more complete than that of its homologues. In the reaction by which this body is formed there wuuld appear to be two distinct stages the first being the formation of the hydride of aceto-salicyl thus :-CO,H CO,H (".".}())+i:}' =(c6f:}O) '~~}" Na Hydride of sodium salicyl.Hydride of aceto-salicyl. the second consisting in the formation of cournarin from this hydride of aceto-sulicyl by the separa,tion of an equivalent of water. OF COUMARIN AND FORMATION OF ITS HOMOLOQUES. 61 Respecting the first change I have found that by treating the hydride of sodium salicyl in a very careful manner the hydride of aceto-salicyl is actually formed.* The second part of this reaction is not so easy of explana-tion viz. from what part of the hydride of aceto-salicyl is the equivalent of water removed. Seeing that this change must be effect'ed either by the dehy- drat'ing power of boiling acetic anhydride or by a temperature not exceeding 300° C.it would not appear very probable that the acetylic radical was interfered with especially as acetic acid is produced when coumarin or coumaric acid is decomposed with hydrate of potassium. It is also evident that the hydride of aceto-salicyl loses its character as an acetate on changing into coumarin ; otherwise when dissolved in a strong solution of hydrate of potassium coumaxin should entirely split up instead of forming coumaric acid. Further it is evident that it has lost its typical aldehydic hydrogen otherwise coumarin would be an aldehyde. Assum-ing these considerations to be correct the change which the hpdricle of aceto-salicyl undergoes on losing an equivalent of water and thereby being converted into coumariii may be represented thus :-Hydride ofaceto-salicyl.Coumarin. According to this formula coumarin is a mixed acid radical consisting of a molecule of acetyl jointed to a molecule of a radical C,H30. This would belong to the same series as cinnamyl and I propose to name it DZptyZ. It will be well to see in what way the reactions of coumarin may be explained by this formula. I will first take the forma-tion of coumaric acid. * This substance possesses all the properties pointed out by theory namely those of an aldehyde and an acetate. It freely combines with bisulphites and with alcoholic hydrate of potassium easily decomposes yielding acetate of potassium and the hydride of potassium-salicyl.I hope shortly to give a full account of this body. VOL. XXI. B' PERKIN ON THE PRODUCTION OF COUMARIN ETC. This acid is formed by the assimilation of an equivalent of water by coumarin through the intervention of hydrat'e of potassium in the same way that alcohol is formed from ethylene by the intervention of sulphuric acid. Coumarin. Coumaric acid. Ethylene. Alcohol. Thus expressed coumaric acid wouId be a phenol and not a true acid and if' we regard the radical salicyl as a phenol as * well as an acid radical,- Salicyl.. coumaric acid likewise becomes a mixed acid radical acetyl- salicyl. The second reaction it will be well to consider is the trans- formation of coumaric acid into acetic and salicylic acids.It will be seen that this change is easy of comprehension the two radicals simply becoming hydrated. CH Coumaric acid Acetic acid. Salicylic acid. (Acetyl-salicyl) To express the formation of the homologues uf coumarin it is evidently only necessary to replace acetyl by other acid radicals. Coumarin and its homologues probably have several isomers corresponding in iiiirnber to tlzc ads isomeric with salicylic and WILLIAMS ON THE PREPARATION OF UREA. 63 if coumarins are simply acid radicals the possible number of such substances capable of existence is enormous. The following is a table of the bodies described in this paper written out according to the foregoing theoretical views. Also of coumaric acid and its probable homologues not yet analyzed-Ace& coumarin } CgH60 :$$$} (Coumarin) Acetyl-diptyl.Propionic coizmarin wanting. Butyric coumalin .. C lHl,O Butyl-diptyl. %2:} Valeric coumarin .. Cl,H,,O gig$} Yalyl-diptyl. Acetic coumaric acid ) C,H30 J Acetyl-(Coumaiic acid) ~9~803 C,H,(HO)O I salicyl. Propionic coumaric acid wanting. Butyric cciurnaric acid C ,W,,O Butyl-hop} salicyl. I am at present studying some new derivatives of coumariii and its homologues with a view of obtaining a clearer insight into their nature