2218 CROSSLEY AND GITLTNQ : SYNTHESIS OE'CCXXX1.-Synthesis of 1 : 1 : 3- Trimethylcyclohexene(cyclo Geraniolene).By ARTHUR WILLIAM CROS SLEY and CHARLES GILLING (Salters'Fellow).SOME years ago Tiemann and Semmler (Ber., 1893, 26, 2708)prepared from the aldehyde citral (geranial) an open-chain hydro-carbon, C9HI6, named by them geraniolene. The constitution ofthis substance (I) follows from that of citral, which was establishedby Barbier and BouveauIt in 1896 (Compt. rend., 122, 393).When geraniolene is shaken with a 60 per cent. solution ofsulphuric acid, an isomeric change takes place, the open-chainhydrocarbon being converted into a mixture of two cyclic hydro-carbons, a- and P-cyclogeraniolene (I1 and 111), in which mixturethe a-variety is present in larger quantity:CMe,: CH*CH,*CH,*CMe: CH, -+ CMe2<E2: :>OH and(1.1 ~ (11.)-CHzCNe(111.)CMe2&,.CQ2>CH2The constitutional formuh of these hydrocarbons were ultimatelydetermined by Tiemann (Ber., 1898, 31, 816, 881; 1900, 33, 3711)from a study of their oxidation with potassium permanganate, theproducts isolated being two ketonic acids, isogeronic (IV) andgeronic (V) acids, together with as-dimethylsuccinic acid and BB-di-methylglutaric acidI : 1 : 3-TRIMETHYLCYCLOHEXENE (CYCLOGERANIOLENE). 2219The formation of the two modifications of cyclogeraniolene wasascribed to the addition of two molecules of water to the moleculeof geraniolene which were subsequently eliminated. According toTiemann, hydroxyl groups became attached to the carbon atomsbearing methyl groups, so that the first stage in the reaction consistsin the formation of a compound of formula VI; this is succeededby ring-formation due to elimination of a molecule of water andsubsequent union of the two carbon atoms marked *:It is obvious that the second molecule of water may be eliminatedfrom the compound (VII) in two different ways, and the formationof the two modifications of cyclogeraniolene is thus explained :A third hydrocarbon having the formula :is a possibility, but no evidence of its presence is recorded.Tiemann did not actually isolate either of the hydroxy-compoundsV I or VII, but a synthesis of 1: 1: 3-trimethylcyclohexan-3-01(VII) has now been effected by a method which leaves no doubtas to its constitution, and it is found that this alcohol can be readilyconverted into cy clogeraniolene, thus affording confirmation ofTiemann's supposition.The starting point was 1 : 1-dimethylcyclohexan-3-one (VIII),prepared by the action of reducing agenh on 5-chloro-1 : l-dimethyl-A~cyclohexen-3-one (Trans., 1907, 91, 81).When this ketone istreated with an ethered solution of magnesium methyl iodide andthe product decomposed with water, trimethylcyclohexanol (IX) isobtained as a well-defined, crystalline substance, melting at 72'5O(X- 1Fuming hydrobromic acid converts the alcohol into 3-broms3 : 1 : 3-t.rimethylcycZohexane (X), which, when treated withalcoholic potassium hydroxide, losses the elements of hydrogen7 F 2220 CROSSLEY AND QILLING : SYNTHESIS OFbromide in two ways, giving rise to the same mixture of hydro-carbons as described by Tiemann.The work of Tiemann on the preparation of cyctogeraniolene wasrepeated by Wallach (Annalen, 1902, 324, 97), who prepared thenitrosate of a-cyclogeraniolene, and proved that it was transformedby the action of alkalis into the oxime of 1 : 1 : 3-trimethyl-A2-cycZo-hexen4-one. The identity of the hydrocarbons described in thepresent communication with cyclogeraniolene has been establishedby preparing this crystalline nitrosate, and from it the above-mentioned oxime ; further, by oxidising the hydrocarbons withpotassium permanganate, when the products isolated were as-di-rnethylsuccinic acid, isogeronic and geronic acids, the two latterbeing identified as their semicarbazones, melting at 195O and 164Orespectively .EXPERIMENTAL.>CH,.I : 1 : 3-Trimethytcyclohexan-3-oZ, CMe,<CI12 CH,*CMe(OH) CH2Thirty grams of 1 : l-dime~hylcycZohexan-3-one (Trans., 1907, 91,Sl), dissolved in an equal volume of ether, were gradually added toa Grignard reagent prepared from 33 grams of methyl iodide and5.7 grams of magnesium turnings in 100 C.C.of dry ether. Theethereal solution was gently boiled on a water-bath for one hour,cooled, and poured into a concentrated solution of ammoniumchloride, t o which ice had been added. The ethereal layer wasseparated, the saline solution extracted three times with ether, themixed ethereal liquids washed, dried over potassium carbonate, andevaporated, when a solid residue (23 grams=70 per cent.of thetheoretical amount) was obtained, which, after drying on porousplate, was recrystallised from dilute alcohol and analysed :0.1061 gave 0.2965 CO, and 0.1209 H,O.C,H,iO requires C = 76-06 ; H = 12.67 per cent.1 : 1 : 3-Tm'methyZcyclohexan-3-ol is readily soluble in the cold inall the ordinary organic solvents, and may be crystallised fromdilute alcohol or dilute acetone, from which it separates in beautifulfour-sided, elongated prisms, having a characteristic, stronglycamphoraceous odour, and melting at 72'5O.C=76*21; H=12-66.3-Bromo-I : 1 : 3-trimethylcyclohexane.Trimethylcyctohexanol, in quantities of 10 grams at one time,were sealed up with 50 C.C. of a solution of hydrogen bromide(saturated at Oo) in small soda-water bottles, which were heatedin a boiling-water bath for one hour.The mixture was poureI : 1 : 3-TItIMETHYLCYCI.OHEXENE (CYCLOGERANIOLENE). 2221into water, extracted three times with ether, the ethereal solutionwashed with a solution of sodium hydrogen carbonate, then withwater, dried, evaporated, and the residue distilled under diminishedpressure, when, after two distillations, 11.5 grams passed overconstantly at SS0/20 mm.:0.1527 gave 0.1375 AgBr.C,H,,Br requires Br = 39-02 per cent.Bromotrimethylcyclohexane is, when freshly prepared, a faintlyyellow liquid boiling at 8 8 O / 20 mm., which, especially on exposureto air, evolves fumes of hydrogen bromide and rapidly decomposes,becoming green, and finally black.The rapidity with which thisdecomposition takes place accounts, no doubt, €or the low result forbromine quoted above.Br = 38-31.1 : 1 : 3-Trimetliyl43- and 42-cyclohexenes. a- and /3-cyclo-Geranwlene,Thirty grams of potassium hydroxide were dissolved in a littlewater, and added to 35 grams of bromotrimethylcyclohexane dis-solved in 150 c . ~ . of absolute alcohol. The whole was heated on thewaterrbath for one hour, cooled, poured into water, and extractedfour times with ether; the ethereal solution was washed, dried, andevaporated, and the residue distilled, when the following fractionswere collected : 110-136O = 2 grams; 136-142O= 13 grams ;142-150° = 3 grams. m e fraction 136-142O was twice redistilledover sodium and analysed:0.1244 gave 0.3971 CO, and 0.1430 H,O.C9H,, requires C= 87.10 ; H= 12.90 per cent.Trimethylcyclohexeme (cyclogeruniolene) is a colourless, refractiveliquid, possessing a pronounced terpene-like odour.It boils at137-140°/760 mm., and has a density of 0.8085 at 15O/15*.This hydrocarbon has also been prepared by the action ofdehydrating agents on trimethylcyclohexanol (potassium hydrogensulphate at 130-140°, and zinc chloride at 160-170°) and byshaking trimethylcyclohexanol with dilute sulphuric acid (D 1-67)for several hours at the laboratory temperature. If this latteraction is prolonged for several days, the principal product is apolymeric modification of the hydrocarbon boiling at 165-170°/30 mm.When dissolved in glacial acetic acid and treated with amylnitrite and nitric acid according to the directions of WallachC = 87.06 ; H = 12.772.222 SYNTHESIS OF 1 : 1 : 3-TKIMETHYLCYCLOHEXENE.(Zoc.cit.), _the mixture of trimethylcydohexenes, prepared by any ofthese methods, yielded the crystalline nitrosate of 1 : 1 : 3-trimethyl-A3-cycZohexene, melting at 103-104°, which by the action of sodiummethoxide was transformed into the oxime of 1: 1 : 3-trimethyl-A%yclohexen-4-one, melting at 128O.The hydrocarbon was oxidised with potassium permanganate asdescribed by Tiemann (Ber., 1900, 33, 3711), when the residueobtained on working up the product partly solidified on keeping.It was spread on plate, and the residue crystallised from water,when it melted at 140O.The identity of this substance with as-di-methylsuccinic acid was proved by the mixed melting-point method,and by preparing from it an anilic acid, which melted at 186O.The porous plate (see above), on extraction with ether, yieldedan oil which was dissolved in alcohol and treated with a solutionof semicarbazide acetate. After some time a solid wils deposited,melting at 185-192O, which crystallised from alcohol, in whichsolvent it is only sparingly soluble, in feathery needles, melting anddecomposing at 198O. (Found, N = 18.46. Cl,Hl,03N3 requiresN=18.34 per cent.) These data prove the substance to be thesemicarbazone of isogeronic acid.On concentrat.ing the mother liquor from the above semicarbazone,a further quantity of crystals was obtained in glistening lamellae,melting, after recrystallisation, at 163O.(Found, N = 18.37.Cl,H,,03N, requires N = 18.34 per cent.) The substance was therefore the semicarbazone of geronic acid (compare Tiemann).It appeared to be of interest, in connexion with other work whichis in hand, to try the action of Grignard reagents, other thanmagnesium methyl bromide, on dimethylcyclohexanone, but theresults are most disappointing, as with increase in the molecularweight of the alkyl group, the yields of the products decreaserapidly, and further work in this direction has been abandoned forthe present.1 : l-DimethyZ-3-ethiyZcyclohexan-3-oZ, prepared by the action ofmagnesium ethyl bromide on 1 : l-dimethylcycZohexan-3-one, is acolourless, refractive liquid, boiling at 94O/ 30 mm., and possessing apenetrating, camphoraceous d o u r :0.1363 gave 0.3851 CO, and 0'1552 H20.C,,H2,0 requires C = 76.93 ; H = 12.82 per cent.The alcohol is readily converted by the action of fuming hydro-bromic acid into 3-bromo-l : 1-dimethyl-3-ethylcyclohexane (b. p.105-106O/ 22 mm.), from which substance hydrogen bromide iseliminated by potassium hydroxide to give a mixture of isomeric1 : I-dimethyl-3-ethylcyclohexenes :C = 77.05 ; H = 12.65MOORE : THE cmsrI'rumn OF GELSEMIUM. 22230.1210 gave 0.3848 CO, and 0.1425 H,O.Dim,ethyZethyZcyclohexene is a colourless, refractive liquid,, boilingC = 86.73 ; H = 13.09.CIoHl8 requires C = 86.95 ; H = 13.04 per cent.at 156O/760 mm.RESEARCH LABORATORY, PHARMACEUTICAL SOCIETY,17, BLOOMSBURY SQUARE, W.C