26 CROSSLEY AND RENOUF : DIHYDROLAUROLENE, DIHYDRO- VI.-The supposed identity of Dihydrolaurolene and Dihydi8oisolaurolcne with 1 : 1 -Dinzethylhexahyclrobenxene. By ARTHUR WILLIAM CROSSLEY and NORA RENOUF, Salters’ Research Fellow. IT was stated in a previous communication (Trans., 1905, 87, 1487) that the main object the authors had in view when preparing 1 : 1-di- rnethylhexahydrobenzene was a comparison of its properties with those of dihydrolaurolene and dihydroisolaurolene, with which hydrocarbons it has been supposed by Zelinsky and Lepeschkin (AInnaZen, 190 1,319, 303) to be identical. As these authors based their conclusions on the physical properties of the hydrocarbons and gave no details of their chemical properties, such as oxidation products, it became necessary to prepare dihydrolauroiene and dihydroisolaurolene, and to investigate them from the chemical standpoint.ISOLAUXOLENE AND 1 : 1 -DIMETRYLHEXAHYDRORENZENE 27 The following is a list of the more important papers dealing with laurolene and isolaurolene, and all references in this communication are to these papers unless otherwise stated.Lacurole ne.-Wreden, Annalen, 1877, 187, 171 j Reyher, Inaug. Dissertation, Leipig, 1891, 51 ; Aschan, Annulen, 1896, 290, 185 ; Noyes, Amer. Chem. J., 1895, 17,432 ; Walker and Henderson, Trans., 1896, 69, 750 ; Zelinsky and Lepeschkin, Annalen, 1901, 319, 311. i s o L a u v o I ene.-Moitessier, Juhresber., 1866 ; Wreden, ibid. ; Damsky, Ber., 1887, 20, 2959; Koenigs and Meyer, Ber., 1894, 27, 3470; Blanc., Bull. sbc.chim., 1898, [iii], 19, 699 ; Zelinsky and Lepeschkin, ibid., p. 307. B i h y d r o I a zc r o lene. Laurolene was first prepared by the distillation of camphanic acid, and is a colourless, highly refractive liquid boiling at 119-122', by far the largest portion distilling at 119.5-120*5". It possesses the properties previously attributed to it except as regards optical rota- tion, which was never found to be as high as + 2 3 O (see p. 38), a point which is being further investigated. Laurolene is not identical with 1 : 1 -dimethyl-A3-tetrahydrobenzene (Trans., 1905, 87, 1600), with which it is isomeric. The conversion of laurolene into its hydriodide is an operation attended with great difficulty, which information would not be gathered from the description given by Zelinsky and Lepeschkin, who state that they obtained more than 70 per cent.of the theoretical quan- tity, boiling at 69O/15 mm., by heating the hydrocarbon with fuming hydriodic acid for five hours in a water-bath. The present authors, although varying the amount of hydriodic acid used and the length of time of, heating, could never obtain more than 25-30 per cent. of the theoretical quantity of hydriodide, boiling much higher than as above stated, namely, 101-106°/33 mm., and a certain amount of unchanged hydrocarbon was always recovered. Zelinsky and Lepeschkin do not quote an analysis of the hydriodide, nor was it found practicable on the present occasion to carry out an iodine estimation, as the substance cannot be distilled even in a vacuum without some decomposition and always contains free iodine.The agent employed by Zelinsky and Lepeschkin for the conversion of the hydriodide into dihydrolaurolene was zinc-palladium, but as experiment showed that reduction of the hydriodide by means of zinc dust and aqueous alcohol leads t o the same result the latter method was employed, as it is much less troublesome to carry out. The process is again a wasteful one, as only 30 per cent. of the theoretical quantity of the pure saturated hydrocarbon is obtained, which is28 CROSSLEY AND RENOUF : DIHYDROLAUROLENE, DIHYDRO- largely due to the fact that during reduction the elements of hydrogen iodide are to some extent removed from the hydriodide, giving rise to an unsaturated hydrocarbon, which is destroyed on treating the raw reduction product with potassium permanganate.That the dihydrolaurolene obtained by the above reactions differs from 1 : 1-dimethylhexahydrobenzene will be seen from the following comparison : 1 : 1-Dimethylhexa- 1 1200 0,7864 { resembling PP-dimethyl- hydrobenzene ... J geranium adipic acid Dihydrolaurolene 11 1 *5--114O 0.7633 camphoraceous oxalic acid oxidation b. p. sp. gr. odour. product. Regarding the probable constitution of dihydrolaurolene, there is not much to be said on the present occasion. Zelinsky and Lepesch- kin have shown that, when laurolene hydriodide is treated with di- methylaniline, the elements of hydrogen iodide are removed, and laurolene is recovered unchanged except that it is optically inactive. If, therefore, laurolene gave oxidation products containing the carbon complex present in the hydrocarbon, as is the case with isolaurolene, the determination of its constitution would not be a difficult matter, but it does not, and it has been found, in accordance with the observa- tions of previous experimenters, that the only definite oxidation pro- ducts obtainable from laurolene are oxalic and acetic acids.It seems probable that, as Zelinsky and Lepeschkin point out, laurolene (ibid., p. 312) is a mixture, for its boiling point is not par- ticularly constant, its behaviour towards hydrogen iodide is not that of a homogeneous substance, and, further, although prepared from pure camphanic acid under precisely similar conditions, its optical activity varies (see p. 38). Moreover, this view is supported by a considera- tion of its magnetic rotation (see p.36) and of the theory of its formation from camphanic acid (I), which takes place as here re- presented : C H , - G l CH,*$?H- CH,-C--CO = 2c02 + CH2*Y- 11. I 1 (pH,), 9 I 7(CH3)2 I c=, CH3 I. It is obvious that the bonds in a substance having formula I1 must at once undergo rearrangement to give a stable compound, and this may occur in a variety of ways, giving rise to pentamethylene or hexamethylene derivatives :ISOLAUROLENE AND 1 : 1-DIMETHYLHEXAEYDROBENZENE 29 111. IV. V. CH,--GH I V*CH, dH2*FH-6H, VI . CH, Experimental evidence is not yet sufficiently complete to allow a definite expression of opinion as to how the reaction takes place, but it may be pointed out that, although dihydrolaurolene is not identical with dihydroisolaurolene, there is, on theoretical grounds, no reason why the former should not contain a proportion of the latter, for, supposing that the intermediate product represented by formula I1 rearranges itself to form substances having either formula I11 or IV, then on treatment with hydriodic acid and reduction of the hydriodide formed there would be produced 1 : 1 : 2-trimethylcyclopentane identi- cal with dihydroisolaurolene.Under these conditions, however, some aa-dimethylglutaric acid should result from the oxidation of dihydro- laurolene, but up to the present stage of the inquiry it has not been found possible to isolate even traces of this acid. D ih ydroisolaurolene. isoLaurolene has usually been prepared by heating isolauronolic acid in sealed tubes for eight hours a t a temperature of 300-340° (Blanc, p.700; Zelinsky and Lepeschkin, p. 307), a process which, as pointed out, frequently means considerable loss on account of the bursting of tubes. A new method was therefore sought, and it was found that if isolauronolic acid is heated with one and a half times its weight of pure anthracene somewhat above the melting point of the mixture, a reaction sets in and isolaurolene slowly distils over, the end of the reaction being indicated by the fact that anthracene sublimes into the neck of the distillation flask. The reaction takes three to four hours for completion, but when once the temperature has been regulated no further attention is required, and the yield of isolaurolene is almost quantitative.When treated with fuming hydrioclic acid, isolaurolene is readily converted into the liquid hydriodide (yield 75 per cent. of the theoretical), which, on treatment with zinc dust in aqueous alcoholic solution, gives from 60 to 62 per cent. of the theoretical amount of dihydroisolaurolene, which hydrocarbon is not identical30 CROSSLEY AKD BENOUF : DIHYDROLAUROLENE, DIRYDRO- with 1 : 1 -dimethylhexahydro benzene, as seen from comparison : 1 : 1-Dimethglhexa- hydrobenzene . . . b. p. sp. gr. odonr. resembling geranium } 120' 0.7864 { sweet cam- Dihydroisolaurolene 11 3-1 13.5" 0.7762 the following oxidation product. @@dimethy 1- adipic acid aa-dimethyl- glutaric acid Constit&ion of Biluyo%oisoZauroZene. As the formula to be assigned to dihydroisolaurolene nahrally depends on the constitution of isolaurolene, the evidence in favour of the latter substance being 1 : 1 : 2-trimethyl-A2-cycZopentene must be very briefly reviewed.Damsky (p. 2959) was the first experimenter to investigate the properties of isolaurolene at all fully ; his oxidation experiments '( did not, however, give rise t o any solid product, but only to oily fatty acids." This oil must have been the ketonic acid, C,H,,O,, described on p. 46, which, on being extracted from the oxidation liquid, is accompanied by small amounts of acetic acid, and does not show any signs of solidificatiou until it has been distilled. In 1898, Blanc definitely established the constitution of isolaurolene in the following manner. Accepting his formula for isolauronolic acid (VII) as correct, he believed isolaurolene to be represented by formula VIII : CH,*F](CH,), =: co, + I p H 3 CH,* 7<""3>2 I p = 3 CH,* C CO,H C'H;CH VII.VIII. that is to say, that during the loss of carbon dioxide no change in the structure of the ring takes place. This was proved by the fact that isolauronolic chloride (IX), when treated with zinc methide, gave rise to the same ketone (X) as is produced by the action of acetyl chloride on isolaurolene in presence of aluminium chloride : "H,*$wH3)2 cII,*c*coc1 A CH,*y(CHd, I EaCH:3 + Zn(CH3)2 \ IX. I Ii-CH, cILI,-F(CH,), Z CH,.C*CO*CH3 CI3,nCH I g*CH3 + CH;COCl ,-" x. Blanc further showed that when isolaurolene is oxidised withISOLAUROLENE AND 1 : 1-DIMETHYLHEXAHYDROBENZENE 31 potassium permanganate there is obtained y-acetyldimethylbutyric acid (XI), previously obtained by him from the oxidation of isolau- ronolic acid (Bull. SOC.chim., 1898, [ iii], 19, 533) : and this ketonic acid, on further oxidation, gave m-dimethylglutaric acid (XII). As Blanc says, the formation of 7-acetyldimethylbutyric acid by the Oxidation of isolmrolene shows that it can only have the constitution represented by formula VIII and no other. ‘‘ Aucune ambiguite ici n’est possible.” Yet Zelinsky and Lepeschkin in 1901 did not accept this conclusion, but regarded isolaurolene as a six-ring compound. Accepting then the foregoing formula (VIII) for isolaurolene, the next point is to prove that when isolaurolene is treated with fuming hydr- iodic acid a t a temperature of 120-125O no change in the nature of the ring is produced.This might seem probable, because isolaurolene, when brought into contact with hydriodic acid at the ordinary tem- perature, gives a solid and very unstable hydriodide; whereas at- 120-1 25O, a comparatively stable and liquid hydriodide is produced. Nevertheless, it is easily demonstrated that this liquid hydriodide con- tains the same carbon complex as isolaurolene itself. For this purpose, the hydriodide was treated with diethylaniline, when it readily lost the elements of hydrogen iodide, giving an unsaturated hydrocarbon, C8HIQ, boiling at 108-1 08*5O, and possess- ing properties identical with those of isolaurolene. I n order that there should be no doubt on this point, the hydrocarbon was oxidised with potassium permanganate, when it yielded 7-acetyldimethylbutgric acid, and this, on further oxidation with sodium hypobromite, gave arc-dimethylglutaric acid. These are the same products as Blanc obtained by the oxidation of isolaurolene (see above), and conclusively prove that no isomeric change takes place during the production of the hydriodide, which must therefore have one of the following formulze : There is, moreover, no reason to suppose that heating this hydriodide with zinc dust in aqueous alcoholic solution would produce a change in the construction of the ring, and this is proved by the fact that when32 CROSSLEY AND RENOUF : DIHYDROLAUROLENE, DIHYDRO- the resulting hydrocarbon (dihydroisolaurolene) is oxidised with diluted nitric acid it gives rise to au-dimethylglutaric acid : that is, to the same oxidation product as isolauronolic acid yields when treated with diluted nitric acid (Blanc, Bull.Xoc. chim., 1898, [iii], 10, 284). These experiments prove conclusively that dihydroisolaurolene is a pentamethylene derivative and is 1 : 1 : 2-trimethyZcyclopenntalze, a deduction which receives striking confirmation from the magnetic rotation of dihydroisolaurolene, and to which Dr. Perkin makes allusion in his report (see p. 36). Zelinsky and Lepeschkin concluded, as a result of their experiments, that dihydrolaurolene and dihydroisolaurolene were identical, a con- clusion which does not seem to be warranted by the results obtained by the present authors. Further, from a consideration purely of the physical properties of dihydroisolaurolene, these authors supposed that it was a hexamethylene derivative, and, since laurolene hydriodide and isolaurolene hydriodide, both of which substances contain the same carbon ring as dihydroisolaurolene, when treated with diethylaniline regenerate lnurolene and isolaurolene respectively, that therefore the latter substances contain a six-membered carbon ring, which '' very probably is also present in isolauronolic and camphanic acids." '' Man konnte weiter gehen und schon voraussetzen, dass die Kamphersaure .. . einen Hexamethylenring besitzt." Komppa's synthesis of cam- phoric acid (Ber., 1903, 36, 4332) is a sufficient answer to the latter suggest ion, Zelinsky and Lepeschkin then argue that dihydroisolaurolene, C8HI6, must be a dimethylhexamethylene, and since it was not identical with 1 : 2-, 1 : 3-, or 1 : 4-dimethylhexahydrobenzene, all of which sub- stances have been described by Zelinsky, i t must be the only remain- ing possibility, namely, 1 : 1 -dimethylhexahydrobenzene, a conclusion which is certainly wrong.They attempt to explain the fact that the boiling point of their supposed 1 : 1 -dimethylhexahydrobenzene (1 14') is lower than the boiling points of the 1 : 2-, 1 : 3-, and 1 : 4-isomerides, because the two methyl groups are bound to one and the same carbon atom, and quote in support of this the fact that 1 : 3 : 3-trimethyl- hexahydrobenzene, which also contains two methyl groups attached to the same carbon atom, boils 4 O to 5 O lower than theisomeric 1 : 2 : 5-tri- methylhexahydrobenzene.We now know chat the boiling point of 1 : 1-dimethylhexahydrobenzene is almost identical with those of theISOLAUROLENE AND 1 : 1-DIMETHYLHEXAHYDROBENZENE. 33 isomeric hydrocarbons, as will be seen from the following table, and therefore the presence of the gem-dimethyl group does not in this case give a compound of lower boiling point than its isomerides : 0 bservers. b. p. sp. gr. 1 : 2-Dimethylhexahydrobenzene (Zelinsky and 1 : 3-Dimethylhexahydrobenzene (Zelinsky and 1 : 4-Dimethylhexahydrobenzene (Zelinsky and 1 : 1 -Dimethylhexahydrobenzene (Crossley and Lepeschkin, Annalen, 1901, 319, 319) ......... 116-118' 0.7733 Naumoff, Be?.., 1895, 28, 781) .................. 1195" 0.7688 Keformatsky, Ber., 1898, 31, 3207) ............119.5-12W Renouf, Trans., 1905, 87, 1498) ............... 120' 0,7864 0.7690 Zelinsky and Lepeschkin further state that, if dihydroisolaurolene were a pentamethylene derivative, it would be 1 : 1 : 2-trimethylcyclo- pentane,and its boiling point would not therefore be higher than ill', because the difference in boiling point for the homologues of this series is about 20°; but as it contains two methyl groups attached to the same carbon atom, so its boiling point would probably be below 11 1'. The boiling point of dihydroisolaurolene (1 : 1 : 2-trimethylcyclo- pentane) is now shown to be 113-113*5', or 22" higher than the boil- ing point of dimethylcyclopentane (91-91-4') as given by Zelinsky and Rudsky (Jour. Buss. Chem. Xoc., 1899, 31, 408), which is an almost identical difference as that found between the boiling points of cyclo- pentane, 50.3-50.7' ( Wislicenus, AnnaZen, 1893, 275, 329), and rnethylcyclopentane (Zelinsky, .I Buss.Chem. Soc., 31, 408) 72-72*2O, namely, 21.5'. The authors desire to express their warmest thanks to Dr. W. H. Perkin, sen., for the interest he has taken in this work, and for kindly determining the physical constants of the hydrocarbons, on which he reports as follows : Densities, Magnetic Rotations, a n d Refractive Powers of Lu u r o Ze n e, B i h y d r o Zacur o Zen e, is o Laur ol e me, a n d B ithydro- i s o l a u r o l ene. .Laurolene. Density : d4'/4'= 0.8097 ; d1O0/10' = 0.8048 ; d15'/15'= 0.8010 ; d2Oo/2O0 = 0.7974 ; d25'/25'= 0.7939. Magnetic rotation : t, sp. rot. Alol.rot. 19.1" 1.1737 5.987 VOL. LXXXIX. D34 CROSSLEY AND RENOUF : DIHYDROLAUROLENE, DIHYDRO- Refractive power : t= 19.5" ; d19*5'/4'= 0.79650. Index of Sp. refraction. 1101. refraction. P i ? p i f. Calculated. refraction, I*- H ...... 1.44253 0.5555 9 61,114 60.5 H ...... 1.45246 0.56806 62.486 H ...... 1,45845 057558 63.314 - - Dispersion Ha - H, = 2.20. Uihydrolaurohe. Density : d4'/4'= OW18 ; d1O0/1O0= 0,7670 ; d15'/15'= 0,7633 ; Magnetic rotation : d20°/200 = 0.7596 ; d25'/25'= 0.7567. t. Sp. rot. Mol. rot. 19.6' 1*0181 8.332 Refractive power : t = 19.8' ; dl9*8'/4O= 0.7588. Index of Sp. refraction. Mol. refraction. ; 5. Calculated. refraction. P-1. P* d If ...... 1.42424 054588 61.138 60.8 H ...... 1.42162 0.55561 62.228 H ...... 142591 0.56126 62.86 1 - - Dispersion Ha - H, = 1.723.isolaztrolene. I)eu.sitg : d-Lo/4* = 0,7953 ; dlOO/lO" = 0.7907 ; d15'/15'= 0,7867 ; dZO0/2Oo= 0.7830 ; d25"/25'= 0.7795. Magnetic rotation : t. Sp. rot. 1101. rot 14.3" 1,1270 8.749 Refractive power : t = ld*1° ; d16°10/40 = 0.785 10.ISOLAUTROLENE AND 1 : I-DIMETHYLHEXAHYDROBENZENE~ 35 Index of Sp. refraction. Mol. refraction. H ...... 1.43227 0.55059 60-565 60.5 H ...... 1.44136 0.563 16 61,847 - H ...... 1.44690 0.56923 62.615 Calculated. refraction. P-2, q p . P. d - Dispersion Ha - H, = 2.050. Dilt,ydroisoZauroZene. Density : d4'/4' = 0.7847 ; dlOo/lOo = 0*7800 ; dl5'/ 15'= 0.7762 ; d20'/20'= 0.7727 ; d25O/25" = 0.7694. Magnetic rotation : t. Sp. rot. Mol. rot. 1 4 ~ 3 ~ 1.0298 8.249 Refractive power : t = 16.2" ; d 1 6 .2 ' / ~ = 0.77463. Index of Sp. refraction. Mol. refraction. refraction. P - 1 P - 1 P- d T P . H ...... 1.43244 0.54534 61-078 H ...... 1.42998 0.55508 62.169 H ...... 1,43398 0 -5 6 02 4 62*815 Dispersion Ha - H, = 1 *7 37. Calculated. 60.8 - - t)n comparing the densities and magnetic rotations of dihydro- isolaurolene and isolaurolene, also of dihydrolaurolene and laurolene, respectively with those of 1 : 1-dimethylhexahydrobenzene and 1 : 1- dimethyl-AWdxahydrobenzene (Trans., 1905, 87, 149l), considerable differences are noticed : Magnetic Densities. Difference, rotations. Differeiice, ......... ;:;:; +0'099 1 : l-Dimethyl-A3-tetrahydrobenzene ... 0'8040 - o,0173 @3:: - o.154 1 : 1-Dimethyl-A3-tetrahydrobenzene ... 0.8040 - o,oo30 ;*iN); + o.084 1 : l-Dimethylhexahydrobenzene 0'7864 Dihydroisolanrolene........................... 0'7762 - o'0102 isoLaurolene ................................... 0 -7867 1 : l-Dimethylhexahydrobenzene ......... 0.7864 Dihydrolaurolene ............................. 0'7633 0'0231 :'ti: fo'182 Laurolene ....................................... 0'8010 I n the cases of dihydroisolaurolene and isolaurolene, me have large and irregular differences, which are dissimilar to those of dihydro- laurolene and laurolene. These iso-compounds are evidently different Crorn all the others of the same composition, and one especial 0 236 CROSSLEY .4ND 1tENoUF : DIHYDROLAUHOLENE, DIHYDKO- peculiarity is that the difference between the magnetic rotations of the saturated and unsaturated products is remarkably small, thus : Mol.rot. Dilference. ............... 0.500. isoLaurolene S.743 Dihydroisolaurolene ...... S-24'3 Now it has been shown that the average influence of uusaturation, mused by the loss of H, in the paraffin series, results in a rise of rotation of +05'20 (Trans., 1902, 81, 292), and that, when these unsaturated chain compounds are joined up by loss of H2 soas to form ring compounds, the result of unsaturation remains practically the same. This has been found to be the case with dihydrobenzene and with 1 : 1-dimethyl-A3-tetrahydrobenzene. This is, however, a much larger effect than that found in the case of dihydroisolaurolene and iso- laurolene ; but i t has been shown that in the lower menibera of the ali- phatic series the differences for unsaturation are exceptionally small, as seen in the halogen derivatives of ethylene and propylene (Trans., 1884, 45, 568).If the individual rotations of the unsaturated hydrocarbons be examined (Trans., 1895,67,261) it will be observed that in the case of amylene the difference amounts to only 0.578, and therefore we may assume that this would be about the influence of unsaturation in the corresponding ring compounds. It is very interesting to note that this is near to that found in the case of isolaurolene, indicating that this substance and its dihydro-derivative are trimethyl five carbon ring compounds. This is quite in agreement with the view of Blanc as regards isolaurolene and the results obtained by the authors of the present communication regarding dihydroisolaurolene.The differences observed in the cases of dihydrolaurolene and laurolene are difficult to interpret; for if these hydrocarbons are related to each other in the same way as dimethylhexahydrobenzene is related to dimethyltetrahydrobenzene, these differences should be similar for each of the properties, whereas they are much larger in the case of dihydrolaurolene. It is, however, worth while calling attention to the difference between the magnetic rotations of laurolene and dihydrolaurolene, which is as follows : Difference. ............. + 0.655. Laurolene.. 8.YS7 Dihydrolaurolene ... 8.332 This, it will be seen, lies between the effect of unsaturation of a five and a six carbon ring and might result if laurolene and dihydro- laurolene were mixtures of such compounds.Zelinsky and Lepeschkin (page 382) have proposed the two bridged ring f o r r n u l ~ f u r isolaurolene and laurolene :ISOLAUROLENE m n I : I-T)IMETHYT,HF,XAHTDRORENZENE. 37 Laurolene. but the magnetic rotations of such compounds mould be very much smaller than those found, because the effect of the bridged ring is quite different t o that of an ordinary double linking (Trans., 1902,81, 266). A comparison of the refractive values of these hydrocarbons, made on the same lines as that of densities or magnetic rotations, does not appear to afford much light in reference to their structure. EX P E R I M E N T A L. Preparation of Laurolene. Bromocamphoric anhydride was prepared according to the directions given by Zelinsky and Lepeschkin (p.310), except that the raw product was crystallised from glacial acetic acid instead of chloroform. The yield was about 75-80 grams from 100 grams of camphoric acid. This anhydride was then converted into camphanic acid by heating with a solution of sodium carbonate (Aschan, Ber., 1894, 2'7, 3506). The yield after crystallising from benzene is 55-60 grams from I00 grams of the anhydride. I n preparing lauroleno from camphanic acid, the very precise details given by Aschan (p. 187) were followed. The yield of laiirolene was 33 grams from 150 grams of camphnnic acid, and its purity was proved by analysis : 0.1 149 gave 0,3665 CO, and 0.1 326 H,O. C = 87.00 ; H = 12.82. C,H,, requires C = S7.27 ; H = 12-73 per cent. Pvoperties of the Hy~~occcrbon.-Laurolene is a clear, colourless, highly refractive liquid boiling at 119-122°/760 mm., by far the major portion distilling at 11 9.5-1 20-5O.It possesses an odour resembling both camphor and turpentine, but much less sweet than that of isolaurolene. With alcoholic snl phuric acid (carried out as previously described, Trans., 1905, 87, 1494), the hydrocarbon gives a green colour turning to bronze-green, and when treated with concentrated sulphuric acid in acetic anhydride solution there is produced a dark bronze-green coloration, changing to deep grass- green. Having observed that when laurolene was treated with hydriodic acid (see p. 40) some of the hydrocarbon remained mattacked and appeared to be iinaltered, except as regards optical activity, it was decided to examine the rotations of some of the preparations of38 CROSSLEY AND RENOTTF : DTHYDROLAUROLENE, DlHPDRO- laurolene.This seemed to be more desirable, as the observations of previous workers regarding this point do not, agree, RS mill be seen from the following table : Reference. Source . Rotation. Aschan (p. 189) . . . . .. . . . .. . .. . , .. ... Camphnnic acid . . . .. . [ uIi - 23.0" Walker and Henderson (p. 752) p o ~ ~ ~ ~ r a ~ ' l ~ ~ e ~ h . y l [ u], - 29.2' Tiemannn (Ber., 1900, 33, 2949) Aminolauronolic acid [u] + 19.9" Zelinsky and Lepeschkin (p. 31 1) [ ulD + 22.9" The last-named authors, after partial oxidation with potassium permanganate, obtained laurolene with a rotttion [aIn + 16*2', and express the opinion that on this account laurolene prepared from camphanic acid may possibly be a mixture of isomeric hydrocarbons. Four separately prepared specimens of laurolene have now been examined, and the following numbers obtained : 1.[a], + 11.4'. 2. Inactive. 3. [a], + 6.6". 4. [ a], + 4.1". This irregular rotation might be put down to a difference in the method of distilling camphanic acid, but Aschan gives such very definite instructions as to temperature and the number of drops of the distillate per minute, that it may certainly be said each pre- paration was carried out, as near as it is possible to do so, under identical conditions. The camphanic mid employed was always in the s m e state of purity, and, moreover, specimens 3 and 4 were prepared from the same bulk of camphanic acid. It, mas then thought that two hours' heating of lanrolene with metallic sodium might cause some change to take place, especially as the liquid becomes dark brown during the heating. Specimens 3 and 4 were therefore examined after drying over calcium chloride, and then at intervals during the heating with sodium, but no changa in the initial rotation was observed, and, so far, no satisfactory explanation of this behaviour has been found.Action of Bromine on Lauro2ene.- When a solution of bromine in chloroform is added to a solution of laurolene in the same solvent, cooled in ice-water, a green colour is at once produced, changing to brown, which is destroyed on further addition of bromine, returning as the bromine is used up, and ultimately the solution assumes a violet colour. If then an excess of bromine is added, the violet disappears as the bromine is absorbed, and the green, and finally violet, colorations return.During the whole operation, clouds of hydrogen bromide are evolved, and on evaporating the chloroform a green resin remains. Having found it iinpossible t o get any idea of the quantity of Camphanic acid . . . . . .ISOLAUROLEXE AXn 1 : 1-DIMETHYLHEXAIIYDROBEX’ZESE. 39 bromine used up in chloroform solution, carbon tetrachloride was tried in its place, as recommended by Aschan (p. 190). TJnder these conditions, bromine is gradually absorbed and hydrogen bromide evolved, but none of the colour changes noticed when using chloroform was observed. When 1,0641 grams of the hydrocarbon were taken, the 6rst indication of a permanent bromine colour was observed when 2.2156 grams of bromine had been added, the required amount for absorption of Br, being 1.5477 grams.Nor was the absorption then quite complete, as further :%mounts of bromine were slowly used up on standing. This does not agree with Aschan’s statement that under the above conditions laurolene absorbs exactly two atoms of bromine and no more. On evaporating the carbon tetrachloride solution, hydrogen bromide was evolved and a green resin remained. Oxidation of Laurolene. (1) Vith 21ritlpic Acid.-Six grams of Inurolene were heated in a flask, attached to a condenser, with 80 C.C. of one part fuming nitric acid and two parts water. The residue obtaiaed from this liquid by working it up in the usual way was proved to consist for the moat part of oxalic acid, together with a minute quantity of a dark oily liquid, smelling of burnt sugar, from which no definite chemical compound could be isolated.(2) With Potassium Permc6nganate.-Twenty grams of the hydro- carbon were suspended in 1 litre of water, and powdered potassium permanganate was gradually added until the coloration became per- manent, a result which required 50 grams and occupied seventy hours. The filtered liquid was evaporated to a small bulk, acidified with sulphuric acid, and distilled in steam. The distillate was neutralised with caustic soda, evaporated to complete dryness, and treated with concentrated sulphuric acid, when a volatile liquid passed over, which was proved to consist of acetic acid by its boiling point, and analysis of a silver salt prepared from it.0.21 10 gave 0.1363 Ag. Ag = 64.60. U,H,O,Ag requires Ag = 64 67 per cent. No product of a definite nature could be isolated from the residue of the above steam distillation, nor were any substances other than acetic and oxalic acids obtained by oxidising laurolene with potassium permanganate in acetone solution, or with a mixture of potassium dichromate and sulphuric acid (compare Aschan, p. 193). The action of a nitrating mixture on laurolene was found to give results coinciding with those recorded by Walker and Henderson (p. 752) and Aschan. The action of nitrosyl chloride on laurolene was tried in the hope of obtaining a solid derivative, but only dark green resinous sub-40 CROSSr,ET AICD RENOUF : DTHYDROTAUROJAENE, DIHYDRO- stances were obtained, similar in appearance to the products of the action of bromine on laurolene. taurolene Hydriodide.Laurolene, in quantities of 10 C.C. at a time, was heated, as directed by Zelinsky and Lepeschkin, with 50 C.C. of fuming hydriodic acid (sp. gr. 1.97) in an ordinary stoppered bottle in a water-bath for six hours. The resulting liquid was poured into water and the whole extracted with ether, the ethereal solution washed successively with water, aqueous sodium bicarbonate, a solution of sodium thiosulphate, and finally with water, dried over calcium chloride, and the residue obtained on evaporating the ether distilled under diminished pressure. After working up 33 grams of laurolene in this manner, the following fractions mere collected at 33 mm.Below 90°=10*5 grams; 101-106°= 18.7 grams; 106-150°=5*4 grams. The fraction below 90° was repeatedly distilled over metallic sodium, when it passed over as a clear, colourless, highly refractdive liquid boiling at 119*5-12lo. 0.1166 gave 0.3719 CO, and 0.1352 H,O. This liquid possessed properties identical with those of laurolene, except that it was optically inactive, It is, however, impossible to state, in view of the data given on p. 38, whether racemisation had taken place or not, as the optical activity of the laurolene used in this experiment was not tested before treatment with hydriodic acid. The fraction 101-106° was a greenish-brown liquid and consisted of laurolene hydriodide, which is very much more unstable than iso- laurolene hydriodide.Zelinsky and Lepeschkin (p. 313) give the boil- ing point of this substance as 69O/15 mm., and state that they obtained 15.5 grams from 10 grams of laurolene, but do not mention the quantity of hydriodic acid used or whether they recovered any unaltered hydrocarbon. Although the experiment was repeated under veryvaried conditions, no better yield of the hydriodidecould beobtained, and there was always recovered a certain quantity of unchanged hydro- carbon which, when again heated with fuming hydriodic acid for six hours, was only partially converted into the hydriodide. The fraction 106-1 50' was not further investigated. C = 87.00 ; H= 12.88. C,H,, requires C = 87.27 ; H = 12.73 per cent. Dihydro Zccuro Zene. Thirty-nine grams of laurolene hydriodide were dissolved in 210 C.C.of 90 per cent. alcohol, and 78 grams of zinc dust mixed with an equal volume of .and added, and the whole heated on the water-bath for tenhonrs and then worked up as previously described (Trans., 1905, 87, 1497). The hydrocarbon was suspended in water and treated with potassium permanganate until no further oxidation took place and the whole distilled in steam, when the hydrocarbon slowly passed over. It was separated from the water, dried with calcium chloride, fractionated over sodium, arid analysed : 0.1016 gave 0.3198 CO, and 0,1318 H,O. C,H,, requires C = 85.71 ; H = 14.29 per cent. Dihydrolaurolene is a clear, colourless, refractive liquid boiling at 11 1.5-1 14*/760 mm. and possessing a sweet camphoraceous odoixr ; it does not absorb bromine nor is i t acted on by potassium permangnnate, and gives no evidence of the formation of a nitro-derivative on treat- ment with a mixture of nitric and sulphuric acids.The yield is very much smaller than in the case of dihydroisolaurolene, amounting to about 35 per cent. of the theoretical quantity from the hydriodide employed. Oxidation with ,Vitric Acid.--Two grams of the hydrocarbon were treated in the usual way with 30 C.C. of fuming nitric acid. Large needle-shaped crystals separated from the residual liquid which were proved to consist of oxalic acid. On evaporating to complete dryness and heating with excess of acetyl chloride, only a minute syrupy residue resulted, which was too small to permit of further examina- tion. After finding that dihydroisolaurolene gave act-dimethylglutaric acid on oxidation with diluted nitric acid, dihydrolaurolene was again oxidised exactly as described on p.44. It was not found possible to establish the presence of even the minutest quantities of aa-dimethyl- glutaric acid in the oxidation products obtained. C = 85.83 ; H = 14.41. Preparation of isolauroZe.rze. isoLauronolic acid was prepared according to the directions given by Lees and Perkin (Trans., 1901, ’79, 341), and the yield obtained was as these authors state, namely, from 45-50 per cent. of the weight of camphoric anhydride used, but only when the purest form of aluminium chloride was employed. isoLauronolic acid, mixed with one and a half times its weight of pure anthracene, was placed in a double-necked (Claisen) distillation flask connected with a condenser and carefully heated, when a reaction began almost as soon as the mixture of substances became molten, and a colourless liquid slowly distilled.At the end of three hours, anthracene began to sublime into the neck of the distillation flask, which denoted that the reaction was almost complete, as on heating for62 CROSSLET AND RENOUF : DIHYDROLAUROLENE, DIHYDRO- two hours longer only one or two grams of hydrocarbon passed over. I n the first experiment, 10 grams of isolauronolic acid were used, but the reaction occiirs eqiially readily when 30 or 40 grams are heated a t one time. The hydrocarbon was dried over calcium chloride and dis- tilled from metallic sodium, when the whole passed over at 10S-109°. For the purpose of analysis, it was again distilled over metallic sodium in an atmosphere of carbon dioxide, when i t boiled quite constantly at 108-108*2O. 0.1332 gave 0.4260 CO, and 0.1532 H,O.C = 87.22 ; H= l24”i. C,H,, requires C = 87-27 ; H = 12.73 per cent. C H, * F( CHJ CH,*CH isolaurolene (1 : 1 : 2 -t,rirnetliyl-A2-cylopentene), I ;C;*CH3 , the yield of which is 85-90 per cent. of the theoretical, is a colourless, mobile, highly refractive liquid boiling at 108-108*2°/742 mm., and possessing a sweet odour resembling both camphor and turpentine. With sulphuric acid in alcoholic or acetic anhydride solution, it gives only a pale straw colour, and on adding a few drops of the hydrocarbon to a cold saturated solution of mercuric chloride and shaking, a cloudi- ness appears, and a sticky, amorphous mass separates, which, after standing for some days, becomes pinkish-brown (compare Zelinsky and Lepeschkin, p.308). When a chloroform solution of bromine is added to a solution of the hydrocarbon in the same solvent, coolod in ice-water, the bromine is absorbed without any evolution of hydrogen bromide, the reaction being a quantitative one for the absorption of two atoms of bromine. C,H,, requires Br, = 160. On careful evaporation of the chloroform solution, a practically colourless, crystalline solid was obtained which, when spread on porous plate, set to a waxF mass somewhat resembling camphor, and having a strong odour of camphor and turpentine. It was twice crystallised from methyl alcohol, in which solvent it is very readily soluble, dried as rapidly as possible, and the bromine estimated.1.1809 absorbed 1-7609 Br. Molecular absorption, Rr = 164. 0.1031 gave 0.1429 AgBr. Br = 58-98. C,H,,Br, requires Br = 59.25 per cent. bH,* CH Br readily soluble in the cold in the usual organic media, but can be crystallised from absolute methyl alcohol, when it, separates in fern-IWLAUKOLENE AND 1 : I-DIMETHYLHEXAHYDROBEKZENE. 43 like aggregates of needles melting a t 80-85'. On standing, it decomposes with evolution of hydrogen bromide and gradually resinifios. Damsky (p. 2961) has described the formation of this compound by the direct action of bromine on isolsurolene, but gave to it the formula C8H12Br2, and in support of this quotes a bromine estimation 60.30, whereas the calculated value for CsHI2Br2 is 59.70.Damsky did not in any way purify his compound, and it would probably contain some higher brominated products, which are formed, as Damsky points out, when bromine acts directly on the hydrocarbon. There can be no doubt that this substance is really the dibromo-additive compound of isolaurolene, for when prepared as above described, no hydrogen brom- ide is evolved. It seemed, however, useless to estimate the carbon and hydrogen, as the calculated numbers for C8H1,Br2 and C,H,,Br, are so close to one another as to prevent any accurate conclusions from being drawn. isoLaurolerze Hydriodide. Quantities of isolaurolene were worked up in the following manner. Ten C.C. of the hydrocarbon and 40 C.C. of fuming hydriodic acid" (sp. gr. = 1.96) were placed in an ordinary narrow-necked, stoppered bottle of 120 C.C.capacity, the stopper wired down, and the whole heated in a glycerol bath for six hours at 120-125'. The contents of the bottle were then poured into water, the heavy oil which separ- ated extracted with ether, the ethereal solution washed successively with water, dilute aqueous sodium carbonate to remove acid, dilute sodium thiosulphate solution to remove free iodine, and, finally, with water. It was then dried over calcium chloride, and, after evaporation of the ether, distilled under diminished pressure. At first, a very small amount of a volatile liquid passed over, which was proved to consist of some hydriodide and unchanged hydrocarbon ; then the thermometer rose rapidly, and the pure hydriodide distilled constantly at 101.5'/33 mm.(Zelinsky and Lepeschkin give the boiling point of this liquid as 75---80°/15-17 mm.) as a practically colourless, oily liquid with a pungent camphoraceous odour. The yield is about 75 per cent. of the theoretical amount. Dih ydyoisolaurolene. Thirty-six grams of the hydriodide were dissolved in 192 C.C. of 90 per cent. alcohol, and 72 grams of zinc dust, mixed with an equal * During the addition of hydriodic acid to the hydrocarbon, the formation of the solid hydriodide was observed (compare Damsky, p. 2961, and Zelinsky and Lepeschkin, p. 308).44 CROSSLEY AND RENOUF : DIHYDROLAUROT,ENE, DIHYDRO volume of sand, added, and the whole heated on the water bath for twelve hours and then worked iip as previously described (Trans., 1905, 87, 1497). A second quantity of 36 grams of the hydriodide was treated in exactly the same manner.The hydrocarbon obtained from both experiments was then suspended in 150 C.C. of water and 5 grams of powdered potassium permanganate gradually added, with constant shaking, when the colour of the oxidising agent remained permanent, even on heating t o the temperature of the water-bath for several hours. The whole was then distilled in steam, when the hydrocarbon passed over very readily, being notably more volatile with steam than dihydrolaurolene (see p. 41). It was then dried over calcium chloride, twice distilled from metallic sodium, and analysed. 0.1205 gave 0.3792 CO, and 0,1554 H,O. C = 85.82 ; H = 14.33. U,H,, requires C = 85.71 ; H = 14-29 per cent..Dihydroisolaurolene ( 1 : 1 : 2-trimethylcycZopentane), C H i p%), I p*CH,, CH,*CH, is a clear, colourless, refractive liquid boiling a t 113-113~5"/750 mm. and possessing a sweet camphoraceous odour. It does not decolorise a chloroform solution of bromine, nor is i t acted on by potassium permanganate. The yield of pure fractionated hydrocarbon is from 60-62 per cent. of the theoretical amount. Oxidation with Fuming Nitric Acid.--Two grams of the hydro- carbon were added t o 30 C.C. of fuming nitric acid, when, on warming slightly, a reaction started which gradually became more vigorous. Heating was therefore discontinued until the action had completed itself, and then the whole was heated for half an hour. After remov- ing the nitric acid in the usual manner and evaporating, the residue solidified.It was spread on porous plate, when a white solid was obtained, which was proved to consist entirely of oxalic acid. Oxidation with Diluted Nitric Acid. Five grams of dihydroiso- laizrolene and a mixture of 26 C.C. of fuming nitric acid and 14 C.C. of water were heated to boiling on a sand-bath in a reflux apparatus with a ground glass attachment, when oxidation took place slowly. After six hours, the unattacked hydrocarbon was removed and heated with a fresh quantity of nitric acid, and this process repeated until all the hydrocarbon had been oxidised. On evaporating the nitric acid liquors to dryness, an oily residue was obtained which slowly solidified. It was heated for two hours with excess of acetyl chloride, the solvent evaporated, and the residue (1.5 grams) distilled, when i t boiled for the most part at 260---265" (boiling point of aa-dimethylglutaricISOLAUROLENE AND 1 : 1-DIMETHYLHEXAHYDROBENZENE. 45 anhydride = 265" ; Blanc, Bull.SOC. cTt,im., 1898, [ iii], 19, 285). A portion was converted into the anilic acid, which crystallised from dilute alcohol in lustrous plates melting a t 141'; nor was this melting point altered on mixing the substance with pure aa-dimethylglutar- anilic acid. The remainder of the anhydride was dissolved in boiling water, the solution evaporated to dryness, and the solid residue crystal- lised from a mixture of benzene and light petroleum, when it separ- ated in bunches of minute needles melting at 83'. It was not con- sidered necessary to analyse this substance, as the melting point was unaltered on mixing with the analysed aa-dimethylglutaric acid obtained by the oxidation of y-acetyldimethylbutyric acid (see p.46). Action of Diethylaniliize on iso Laurolene Hydviodide. Thirty-three grams of the hydriodide and 50 grams of freshly dis- tilled diethylaniline were heated in a long-necked distillation flask attached t o a condenser, a thermometer being inserted in the liquid. The first signs of a reaction commenced at 150°, when the source of heat was removed. The temperature gradually rose to 154", when the whole suddenly became turbid and a rather vigorous reaction set in, which maintained the temperature of the mixture at 15'7". When com- plete, the thermometer was raised out of the liquid and the whole heated until everything boiling below 160' had passed over.The dis- tillate was then suspended in water, hydrochloric acid added, and dis- tilled in steam, and the separated hydrocarbon washed with water, dried over calcium chloride, and fractionated. It contained halogen, which could not be completely removed by a second treatment with diethyl- aniline, and it was therefore heated for two hours with 100 C.C. of a boiling saturated solution of alcoholic potassium hydroxide and dis- tilled in steam, the distillate poured into a large volume of water, and the separated hydrocarbon dried over calcium chloride and dis- tilled over sodium, when all but a few drops passed over between 108" and 109". This was again distilled over sodium in an atmosphere of carbon dioxide, when it boiled constantly at 108-108.5" and gave the following numbers on analysis : 0.1 11 1 gave 0.3558 CO, and 0.1278 H,O.C8H,, requires C = 87.27 ; II: = 12.73 per cent. This liquid, which was obtained in almost theoretical amount, had a sp. gr. 15"/15" = 0.7857, gave a solid dibromide melting at 80--85", and in other properties was identical with isolaurolene. 0zidcctioi-L with Potassiu~n I~erma?agccnate.--Fifteen grams of this hydrocarbon were suspended in 375 C.C. of water, and a 4 per cent. solution of potassium permanganate added during constant shaking. C = 87.34 ; H = 12.7s.46 DIHY DROISOLAUROLENE. The permanganate was used up fairly rapidly a t first, but for the completion of the reaction, which required 1030 C.C. of the oxidising agent, it was necessary to heat on the water-bath to a temperature of 60-65'. The solution was then filtered from manganese dioxide, which was washed with hot water, and the combined filtrate and washings evaporated to about 150 c.c., acidified with dilute sulphuric acid, and extracted ten times with ether. The ethereal solution was dried over calcium chloride, the ether evaporated, and the residue distilled under diminished pressure. At 47 mm., a few drops of a liquid smelling strongly of acetic acid first passed over, but the main portion (5 grams) distilled at 180-195' and solidified almost com- pletely after standing in a cool place for thirty-six hours. It was spread on porous plate and purified by crjstnllisation from water, in which it is very soluble, and from which it separated in transparent, four-sided prisms melting a t 48.5' ; nor was this melting point lowered on mixing the substance with dimethylhexanonic acid, kindly sent to us by M. G. Blanc. It gave the iodoform reaction, characteristic of ketonic acids containing the group CH,*CO-, and on analysis the following numbers were obtained : 0.1081 gave 0.3400 CO, and 0.0868 H,O. C8H,,0, requires C = 60.75 ; H = 8-86 per cent. These data prove conclusively that this substance is identical with the y-acetyldimethylbutyric acid (dimethylhexanonic acid) obtained by Blanc (p. 702) by the oxidation of isolaurolene. This acid was then further oxidised with sodium hypobromite (Blanc, ibid.). The oily oxidation product was heated with excess of acetyl chloride for two hours, the anhydride thus obtained distilled, and the portion boiling at 260-265O further examined, A portion was dissolved in boiling water, the solution evaporated to dryness, when it a t once solidified, and after recrystnllisation from a mixture of benzene and light petroleum melted a t 83'; nor was this melting point altered on mixing with pure aa-dimethylglutaric acid, kindly sent to us by M. G. Blanc. 0 = 60.55 ; H = 8.92. 0.1019 gave 0.1960 CO, and 0.0664 H,O. C7H1,0, requires C = 52.50 ; H = 7.50 per cent, Another portion of the distilled anhydride was converted into the anilic acid, which crystallised from dilute alcohol in lustrous plates melting a t 140-1 41°, the melting point of pure aa-dimethylglutar- anilic acid being 141". CY = 52-45 ; H = 7-24. RESEARC'IL LABORATORY, ~'HAKMACEU'I'ICA4L ~OCIISTY, 17, BLOOMSBURY SQUARE, W. C.