134 CHAPMAN : SANTALENIC ACID. XI1 I. -San talenic Acid. By ALFRED C. CHAPMAN, F.T.C. A FEW years ago, in conjunction with Mr. H. E. Burgess, I undertook an examination of the hydrocarbon obtained by distilling santalol with phosphoric oxide, chiefly for the purpose of comparing its properties with those of cedrene. In the preliminary note in which the results of this investigation were given (Proc., 1896, 12, 140), reference was incidentally made to the Formation of a crystalline acid by the action of oxidising agents on oil of sandal-wood, for which we suggested the name sccntalenic acid. At that time circumstances compelled me to discontinue the work, but recently I have been able to make a f u r - ther study of the properties of this acid and its salts, as well as of the conditions under which it is most readily formed, with the results detailed in this paper.In my earlier experiments, that fraction of the sandal-wood oil which boiled at 301--306' (corr.) was used, but I soon found that it was much simpler and more economical to work with the oil itself. Of the samples of oil used, which were all of undoubted genuineness, three were specially distilled for me. As the result of numerous experiments made with the object of ascertaining the conditions under which the best yield was obtained, the following procedure was finally adopted. To 20 C.C. of the oil in a large flask an aqueous solution of potassium permanganate containing 50 grams per litre is added in successive quantities of about 20 C.C.CHAPMAN : SANTALENIC ACID.135 a t a time, thecontents of the flask being thoroughly shaken after each addition. At first, the permanganate is rapidly reduced with the de- velopment of a considerable amount of heat, but when about two- thirds of the solution has been used the oxidation proceeds more slowly. After the whole has thus been added, and the reduction is complete, the oxides of manganese are filtered off, and the filtrate is acidified with sulphuric acid. The precipitated santalenic acid, after having been allowed t o stand for a short time, is filtered off, thoroughly washed with cold water, and dried on a porous tile. Working in this manner, an average yield of 20 per cent. was obtained, but it was found that this depended to some extent on the origin of the oil used, as well as on the rate at which the oxidation was allowed to proceed, The air-dried acid is then dissolved i n alcohol, and water added until the point at which precipitation of the acid occurs is nearly reached.On allowing this solution to stand in a cool place for some hours, the santalenic acid crystallises out in large, transparent plates, and may be further purified by a second crystallisation. After drying in a vacuum over sulphuric acid, two different preparations were analysed, with the following results : 0.2010 gave 0.5540 CO, and 0.1695 H,O. C= 75.17 ; H = 9.36. 0.2105 ,, 0.5810 GO, ,, 0.1800 H,O. C=75*28 ; H=9.50. Cl3Hz0O2 requires C = 75.00 ; H = 9.61 per cent. Titration of ths Acid with Xodcb.-Sodium hydroxide (prepared from sodium) containing 0*00506 gram Na per C.C.was run into a solution of the acid in dilute alcohol, phenolphthalein being used as indicator. 0.494 gram of the acid required for neutralisation 11.4 C.C. of soda solution (= 0.0576 gram Na). For a monobasic acid of the formula C13H2002, 0.0546 gram Na would be required. Molecular Weight.-Two determinations by the freezing point method, using acetic acid as solvent, gave the following results : Depression of Weight of acid. Weight of solvent. freezing point. Mol. weight. 0.185 gram. 8.807 grams. 0-41 9' 194 0.388 ,, 8.430 ,, 1*030° 173 These numbers are in fair accordance with the molecular weight corresponding with the formula C,H,,O,, namely, 208. Using benzene as a solvent, much higher numbers were obtained, but it is well known that many organic acids give abnormal results in benzene solution.Santalenic acid crystallises in thin, colourless plates having a bril- liant pearly lustre, is insoluble in water, but dissolves readily in all the ordinary organic solvents. It melts at 76O, boils without decom- position at 189O (corr.) under a pressure of 25 mm., and can be distilled L 2136 CHAPMAN : SANTALENIC ACID. with steam. Santalenic acid is dextrorotatory. A determination of its specific rotatory power in solution in 90 per cent. alcohol gave the following numbers : c = 10 ; l = 2 dcm. ; a, = 3'37' ; t = 20' ; whence [.ID = + 18.05O. The above number is the mean of two closely agreeing observations, working with different specimens of the acid. When solutions of the metallic salts indicated below were added to an aqueous solution of sodium santalenate, the following results were observed : Gopper sulphate ............Nickel sulphate ............ Magnesium sulphate ...... Zinc sulphate ............... Silver nitrate ............... Mercuric chloride ......... Mercurous nitrate ......... Ferric chloride.. ............. A pale blue precipitate. A pale green precipitate. No reaction. A white precipitate. A white, curdy precipitate. A white precipitate. A white, granular precipitate. A buff-coloured, granular precipitate. Sodium Salt.-This salt was prepared by neutralising a solution of the acid in dilute alcohol with caustic soda, and is soluble both in alcohol and in water. 0,649 gave 0.198 Na,SO,. Na = 9.88. C,,H1,02Na requires Na= 10.00 per cent. Potassium 8alt.-Prepared in a similar manner to the sodium salt.It forms a roughly crystalline, deliquescent mass, soluble in alcohol and in water. 0,332 gave 0.117 K2S04. C,,H,,O,K requires K = 15.86 per cent. Ammonium Salt.-The acid dissolves in dilute aqueous ammonia, but on evaporating the solution ammonia is given off and a residue of the acid left. Silver SccZt.-On adding silver nitrate to solutions of any of the fore- going salts, a white, curdy precipitate is formed which is but slightly soluble in water and not greatly affected by light. After being dried i n a vacuum over sulphuric acid, it was analysed with the following result : K = 15.81. 0-208'7 gave 0.0725 Ag. C,,H,,O,Ag requires Ag = 34.29 per cent. Barium Salt.-This salt may be obtained either by adding barium chloride to a strong solution of the sodium or potassium salt, or by Ag= 34-74.CHAPMAN : SANTALENIC ACID.13'7 neutralising a solution of the acid in dilute alcohol with baryta. is very appreciably Roluble in water. It 0,098 gave 0.042 BaSO,. Ba= 25.20. (C,,H,,O,),Ba requires Ba = 24.86 per cent. Strontium 8ccZt.-Prepared in a similar manner to the barium salt. It is more soluble in water and more distinctly crystalline than the latter. 0*101 gave 0.037 SrSO,. Sr= 17.46. (C1,Hl,O,),Sr requires 8r = 17.39 per cent. The calcium, lead, and copper salts were also prepared and analysed (C,,H,,O,),Ca requires Ca= 8.81. (C,,H,,0,)2Pb ?, P b = 33.33. ,, P b = 33.70 ), (C13Hl902) 2cu 9 9 Cu=13*29. ,? C~=13*36 ,, with the following results : Found Ca = 9-10 per cent.Nethyl Ester, C,,H190,*CH,.--Dry hydrogen chloride was passed into a well-cooled solution of the acid in about six times its weight of methyl alcohol. When the gas ceased to be absorbed, the contents of the retort wera poured into water and the excess of hydrochloric acid carefully neutralised with soda. The precipitated methyl santalenate was then extracted with ether, the ethereal solution dried over calcium chloride, and the ether separated by distillation. The methyl ester then remaining was purified by distillation under reduced pressure, almost the whole of it boiling a t 232-234' under 35 mm. It is a colourless, oily liquid, possessing a faint but agreeable smell, and has a sp. gr. 1.0132 at 1 5 O / 1 5 O . It is lsvorotatory, producing a rotation of - 18"13' in a 100 mm.tube at 20'. On analysis, the following results were obtained : 0.166 gave 0.460 CO, and 0.144 H,O. C,,H2,0, requires C = 75.67 ; H = 9.91 per cent. Bromine Derivative.-Santalenic acid was heated with an excess of bromine in chloroform solution for two days under a reflux condenser, hydrogen bromide being liberated in considerable quantity. On dis- tilling off the chloroform, an oily residue was left, which on standing solidified to a crystalline mass. Very great difficulty was experienced in purifying this by crystallisation, owing to its great solubility in almost all the ordinary organic solvents, and to its marked tendency to separate as an oil. From a mixture of benzene and light petroleum, however, small needle-shaped crystals were obtained, but they were undoubtedly still contaminated with some of the bye-products of the bromination process, and attempts to further purify them faiIed. These C = 75-6 ; H = 9.63.138 CROSSLEY : THE INTERACTION OF crystals melted a t 114--115O, and contained Br=40*8 per cent., a dibromosantalenic acid of the formula CI3Hl8O2Br2 requiring BF = 43.7 1 per cent. In the oxidation experiments above described, the filtrates from the santalenic acid on extraction by ether yielded an oily acid liquid having a peculiar and characteristic odour. The silver salt prepared from this, darkened rapidly on exposure to light, and was much more soluble in water than silver santalenate. This acid is now being studied. Acetic acid and carbon dioxide were also produced in small quantities. It seems not improbable that a further study of the derivatives and decomposition products of santalenic acid may throw some light upon the constitution of the so-called santalols which form the chief con- stituents of the oil.