POPE : RESOLUTION OF RACEMIC CAMPHOROXIBIE. 1105 cx. -The Appl ica t bz. qf Po we 1fu7 Opticnlly Active Acids to tJie Resolzctioiz of ExternaIly Compensated Bccsk Sicbstajizccs. IZesoliitioir of Ruccnzic Cay~hor- OX2132t~, By 11’ ILLIAN JACKSOX POPE. ALTHOUGH tartaric acid may be used in separating the constituents of inactive mixtures of powerful optically active bases, being a weak acid it cannot be successfully used in conjunction with weak bases. I n the present communication, it is shown that the separation is readily effected, even in the case of so weak a base as cnmphoroxime, by means of the strong acid Reychler lias prepared by sulphonating camphor, This acid mas chosen instead of destro-a-bromocainphorsulphonic acid, because it is not so hygroscopic as the latter, and it is possible, there- fore, t o avoid access of water in working with it.Raceinic camphorosiine (60 grams) and carefully purified dextro- camphorsulphonic acid (90 grams) are dissolved in a small quantity of boiling acetone; as the liquid cools, a crystalline, but not homo- geneous, product separates, of which f iirther quantities may be obtained from the mother liquor. The whole of the crystalline material produced in the operation is then fractionally crystallised from boiling ether in a series of beakers, the mother liquors going in one direction through the series, and the crystalline deposits in the other. As the systematic fractionation proceeds, it is noticed that the deposits become more sparingly soluble in the ether, and ultimately two pure products are isolated ; the less soluble substance is dextroczmphoroxime* dextrocainphorsulphonate, and the more soluble is lsvocamphoroxime dextrocamphorsulphonate. * Thr: name dextrocainplioroxiiiic is retniucd for the hvorotatory oxiiue obtained from dex t rocamplior.1106 FOPE : RESOLUTION OF RACEMIC CAMPHOROXIME, Bextvocampho~oxime Bextrocam~horsuJphonate, ~,,~Hl,NoOH,C,oHI,O*SO,H + H,O, Dextrocamphoroxime dextrocamphorsulphonste separates in long, colourless, transparent needles from its ethereal solution ; it is very soluble in alcohol, benzene, acetic acid, chloroform, and most other organic solvents, and tho solutions on evaporation usually become syrupy, and crystallise with difficulty. It is very sparingly soluble i n ethylic acetate or ether and is precipitated as an indistinctly crys t a l h e mass on adding light petroleum to its solution in benzene.On spontaneous evaporation of its cold acetone solution, i t separates in magnificent, lustrous, transparent, orthorhomhic tablets, sometimes 30mm. in length (Fig. 1). The pinacoid 6(010’, is predominant, and the dome ~ ( 1 0 1 ) is the next best form represented ; the form p(110) is larger than p’!210], and both are larger than the pinacoid af100). All the forms observed give fairly good results on measurement. The crystals exhibit no external signs of hemiheclral structure, but there is a very perfect cleavage parallel to t(010), aid on etching cleavage surfaces. with benzene, etch-figures of the appearance represented in Fig. 2 are formed ; two of the bounding sides of these figares appear FIG.1. PIC. 3. a parallel to each other arid to the axis-c, but the other two sides seem t o be not parallel, and to make different angles with the axis-a. It is very difficult to be absolutely sure of t,his, but the etch-figures seem to indicate the sphenoidally hemihedral crystalline structure of the material. Crystalline system.-Orthorhoruhic : Sphenoidal hemihedrism. : 6 : c = 1*2024 : 1 : 0.8943. Forms observed.-a(100), b(010), p{llO), p’{210), ~ { l O l ] .POPE : RESOLUTION OF RACEMIC CAMPHOROXIYE. 1107 The following angular measurements were obbained : Angle. bp =010:110 3?p' =11o: 210 up' = l o o :210 p'p'= 210 : 2 i o 0,. =loo : 101 P,. = l o 1 : 101 pr =110:101 p't =210 : 101 Number of measurements. 42 17 19 14 23 39 12 5 Limits.39'1 6'-40'18' 18 51-10 34 30 45 -31 26 61 30 -62 28 5" 59-54 1 72 46 -73 35 67 1-68 9 53 47 -59 34 Mean. 39'4 5' 19 12 31 3 61 59 53 29 73 17 67 38 58 11 - Calculated, - 19'1 4' 31 1 62 2 53 21'5 67 34 5 9 14 - The acute bisectrix emerges perpendicularly through a cleavage plate ; the optic axial plane is a( 100) arid t.he axis-b is the acute bisectrix. The optic axial angle is large, and the double refraction positive in sign. After melting on n microscope slide and cooling, the material crystal- lises very slowly ; crystallisation may be started and caused to proceed fairly rapidly by cwtiously warming the preparation. The crystal- lisnt,ion is very confused, but consists mainly of long needles, many of which lie perpendicularly to the acute bisectrix of n large optic axial angle ; the double refmction is positive in sign, and this modification is crystallographically identical with tlie crystals deposited from the acetone solution. Deutrocamphoroxime dextrocmphorsulphonate has an odour of camphoroxime, and on exposure to air the percentage of sulphur grad- ually increases, owing to volatilisatiou of the osime.The carefully purified material crystallised from acetone, pomderotl, and dried for 8 short time in the air, melted at 91-93", and gave the following results on analysis : 0.1785 gave 0.37'78 CO, and 0.1341 H,O. 0.3528 ,, 0.2113 EaSO,. S = 5.29. 1.1331 required 27.1 C.C. X / l O NaHO for neutralisation. C,oH,O-SO,H C=57*72 ; H=8*34. 0.1964 ,, 0,4140 CG, ,, 0.1 494 H,O. C: = 57.49 ; IT = 8.46.= 55.49. C,oH,30,NS + H,O requires c1 = 5'7.55 ; H = 8.39 ; S = '7.67 ; C,,H1,O*SO,K = 55.63 per cent. The rotation constants of the salt were determined in absolute alcohol solution; 0.4377 gram, made up to 25 c.c., gave Q~ + 0.15' in a 200 mm. tube a t 21' ; whence [ + 4.3' and [&I JD + 1'7.9'.1108 POPE : RESOLUTION OF RACEMIC CAMPHOROXIME. L~voccc~n~~horoxinze Dextrocccmp~orszcZ~~onc~t~, ClOHl,N*OH,C,,H,,O*SO3H + H,O. Lzevocamphoroxime dextrocamphorsulphonate is even more soluble in the ordinary organic solvents than the salt of dextrocamphoroxime, and the solutions in alcohol, benzene, and acetic acid become syrupy on evaporation in the air. It crystallises on spontaneous evaporation of its solutions in ether, ethylic acetate, and acetone in tiny needles melt- ing a t 90-91', and attempts to obtain measurable crystals were unsuccessful.The small crystals are remarkably similar to those of dextrocamphoroxime dextrocamphorsulphonate in shape and crystallo- graphic properties ; they are flattened upon a six-sided face, b(010), and the acute bisectrix emerges nearly perpendicularly through this face. The double refraction is positive in sign, and the optic axial angle is large ; the plane angle between the two faces corresponding to (101) and (101) on the salt of dextrocamphoroxime was measured as 111-117°, as against 107' on the latter compound. After melting the substance on a microscope slide under a cover slip, it crystallises very slowly a t the ordinary temperature from centres in long, flattened needles j these are crystallographically identical with the crystals deposited from solution, and their formation is hastened by gently warming the plate.The following analytical results, obtained with material crystallised from acetone, powdered and dried in the air, shorn that the salt has the same composition as that from dextrocamphoroxime : 0.1865 gave 0.3937 CO, and 0.1407 H,O. C = 57.57 ; H = 8.38. 0.2197 ,, 0.463'7 CO, ,, 0.1663 H,O. C = 5'7.56 ; H= 8.41. 0.3804 ,, 0.2371 BaSO,. S= 8.64. 1-2285 required 29.4 C.C. A7/10 NnI-fOfor neutralisation. CloH,,0*S03H C,oH3,0,NS + H,O requires C = 57.55 ; H = 8.39 ; S = 7.67 ; CloHl,O*SO,H = 55.63 per cent. Although it seems to be proved by the analytical results given above that these two salts contaiu water of crystallisation, yet they are both decomposed on addition of water, with separation of the cor- responding camphoroxime.I n order to identify these, the salts were treated with water, when flocculent precipitates of the camphoroximes separated ; the solutions were just neutralised with ammonia and the precipitates filtered off, washed, dried, and crystallised from hot alcohol, 0.5765 gram of the oxime obtained from dextrocamphoroxime dextrocamphorsulphonate, made up to 35.2 C.C. with absolute alcohol at 21°, gave aD - 1.89' in a 200 mm. tube ; whence [.IZ, - 41.3", prov- ing the material to be dextrocamphoroxime, = 55.51.POPE : RESOLUTION OF ItACEMIC CAMPHOROXIME. 1109 0,5870 gram of the oxime prepared from laevocamphoroxime dextro- camphorsulphonate, made up to 25.1 C.C.with absolute alcohol at 22*5", gave + 1-95' in a 200 mm. tube ; whence [.ID + 41*7', proving the substance t o be laevocamphoroxime. A consideration of the molecular rotatory powers of dextro- and lsvo-carnphoroxime dextrocamphorsulphonate suggests very strongly t h a t these salts are wholly dissociated in alcoholic solution ; if such were the case, the difference between the molecular rotatory powers of the two compounds should be twice the molecular rotatory power of camphoroxime in alcoholic solution. I n fact, the numbers are 166.8 - 17.9 = 1489 = 2 x 74.4, whereas the molecular rotatory power of active camphoroxime in alcoliolic solution is 70" or 71"; the mole- cular rotatory powers, 70' and 74,' are equal within the rather wide limits of experimental error involved in dealing with these com- pounds.It might possibly bo expected t h a t other salts of tho camphoroximes should similarly dissociate in alcoholic solution ; Forster (Trans., 1897, 71, 1045') has given the specific rotatory power of dextrocamphoroxime hjdrobromide as [ alD - 35*S0, whence the molecular rotation may be calculated as - 88*'7', which, if the componnd dissociated in the alcoholic solution, should be equal t o the molecular rotatory power of dextrocamphoroxime, namely, [MI,, - 7 1 O . A consideration of the foregoing 1vor.k will make it obvious that we are for the first time in possession of a method for resolving ex- ternally compensated osimes into their optically active components, and that i t is therefore now possible, in many cases, to separate racemic ket.ones and aldehydes by purely chemical methods. Many im- portant applications of the new method are evident, such, for instance, as to the elucidation of the constitution of oximos. No chemical method affording direct evidence has yet been devised for judging between Ilnntzsch and Werner's and rival hypotheses as to the con- stitution of the oximes. According t o the one view, however, 0 N-phenylbenzsldoxime has the constitution CHPh<hph, and hence contains an asynimetric carbon atom, whilst, according t o other views, the constitution contains no asymmetric carbon atom, a distinction which may admit of recognition in this, or similar cases, by the use of a method like that now described. Experiments are in progress with this object in view. 1 % ~ hearty thanks are due to the Research Fund Committee of the Chemical Society for a grant defraying the cost of the materials used in this work. GOLDSMITIIS' IXSTITUTE, NEW Ceoss.