EXTERNALLY COMPENSATED TETRAHYDROQUINALDINE. 21 99CCXXVIII.-Extenzally Compensated Tetrahydroquin-aldine (Tctrahydro - 2 - methylqzcinolirbe) uncl itsOptically Active Components.By WILLIAM JACKSON POPE and JOHN READ.THE resolution of externally compensated tetrahydroquinaldine(tetrahydre2-methylquinoline) into its opti.cally a t i v e componentswas effected by Pope and Peachey (Trans., 1899, 75, 1066) bycrystallising its hydrochloride (two equivalents) with ammoniumd-a-bromocamphor-?r-sulphonate (one equivalent) in aqueous solu-tion ; the deposit consists of practically pure I-tetrahydroquinaldined-a-bromocamphor-n-sulphonate. The d-tetrahydroquinaldine wasisolated from the mother liquors by fractional crysta-llisation of thebenzoyl derivative prepared from the separated crude d-base andsubsequent hydrolysis of the pure benzoyl-d-tetrahydroquinaldine.The method thus briefly described affords an easy method for thepreparation of I-tetrahydroquinaldine, but the isolation of theenantiomorphously related base is lengthy and difficult; in thepresent paper a method is described by means of which the twoenantiomorphously related bases can be readily prepared in a state ofhigh purity.bExternally Compensated Tetrahydroquinaldine.This base was prepared, in the manner previously described, asa colourless oil, boiling at 196O/207*5 mm.; at the ordinary tem-perature it is a mobile liquid which shows no tendency to crystallise,and, on cooling in boiling liquid air, it solidifies to a hard, resinousmaterial, which does not crystallise even after long exposure t o thelow temperature thus obtained.When, however, a few drops ofthe base are dissolved in ten times their volume of light petroleum,and the solution cooled in boiling liquid air, tetrahydroquinaldinecrystallises out as a mass of white needles; on inoculating carefullypurified externally compensated tetrahydroquinaldine with thesecrystals at the ordinary temperature, crystallisation at once sets in,and after the lapse of some hours the whole of the base becomesconverted into ilr hard, crystalline mass.It is thus evident that at the ordinary laboratory temperatureexternally compensated tetrahydroquinaldine is a supercooled liquid ;no other method than the one above described has get been foundfor causing the crystallisation.In all probability, the fact thatcrystallisation can only be started by such an uncommon methodas that just described is responsible for the observation not havin2200 POPE AND READ : EXTERNAT,LY COMPENSATED TETRAHYDRO-been previously made that the modification of tetrahydroquinaldinestable at the ordinary temperature is a crystalline one.A specimen of externally compensated tetrahydroquinaldine,prepared from a sample of the hydrochloride which had beenrepeatedly crystallised from acetone, after having been caused tocryshllise in the manner indicated, melted at 20'75O ; after meltingthe crystalline mass, cooling it to 15O, and inoculating the liquidwith the crystalline base, a standard thermometer immersed in thesolidifying substance showed that the temperature rose to 20'75Oduring crystallisation.This may therefore be taken as the meltingpoint of externally compensated tetxahydroquinaldine. It isinteresting to note that on preserving a quantity of the crystallinematerial in contact with the liquefied substance at the laboratorytemperature, the mass of minute crystals gradually becomes con-verted into several large rhombohedra; the latter grow to a diameterof four or five centimetres, and are very transparent, with highlyplane faces. A good example is thus afforded of the well-knownfact that the larger crystals present in contact with a solution tendto grow a t the expense of the smaller ones (Curie, Bull. SOC. Min.franc., 1885, 8, 145).Preparation of Ammonium d- and 1-a-Bromocamphor-n-sulphonat es.For the preparation of the large qua.ntities of ammonium cl- andI-a-bromocamphor-7r-sulphonates required in this and similar work,the sulphonation with chlorosulphonic acid (Kipping and Pope,Trans., 1895, 67, 356) is inconvenient, and may be replaced by aslight modification of t.he method first used by these authors(Trans., 1893, 63, 577).A mixture of fuming and 100 per cent.sulphuric acids is made of such concentration that a-bromocamphordissolves in it to a deep amber-coloured solution, and is not pre-cipitated by pouring on to ice; the concentration of the acid usedrequires careful adjustment, and a suitable concentration was foundto have the density 1.865 at 15O, and to consist of 200 C.C. of100 per cent.sulphuric acid with 75 C.C. of 65 per cent. sulphurtrioxide. This quantity of acid, cooled to the ordinary temperature,readily dissolves 95 grams of d-a-bromocamphor, and simultaneouslythe temperature rises to about 50°. After agitation for half aminute, the mixture is poured through a large funnel filled withcrushed ice, when an insignificant separation of unchanged bromo-camphor occurs; if the acid used is too concentrated, thesulphonation product suddenly carbonises with evolution of torrentsof sulphur dioxide. It is convenient to sulphonate a kilogram ofd-a-bromocamphor in quantities of 100 grams at a time, and almostto neutralise the diluted solution with milk of lime, completinQUINALDINE AND ITS OPTICALLY ACTIVE COMPONENTS. 2201Anamoniumd-a- Bromocamphor-n-su Zphoncite.2.0439 grams in 50 C.C.NWD line).Hg(ye1low). Hg(green).a $13.94" +14*72" +17*30"[u] +85.25 $90.02 -!-105*SOAmmonium1 -a- horn ocnmphor- rr-sulphonate.2.0150 grams in 50 C.C.Na(o line). Hg(ye1low). Hg(green).- 13.62" - 14'47" - 16-97" - 84 '58 - 89-85 - 105.38Resolution of Externully Compensated Tetraliydro~uiizaldine.On treating racemic tetrahydroquinaldine hydrochloride withrather less than half an equivalent of ammonium d-a-bromocamphor-Ir-sulphonate, as already described (Trans., 1899, 75, 1066), thegreater part of the Z-base separates as the sparingly soluble Z-tetra-hydroquinaldine d-a-bromocamphor-n-sulphonate ; the latter salt isobtained in a state of high purity by crystallisation from alcohol.The mother liquors, containing the whole of the d-base, are thentreated with sodium hydroxide, the base separa.ted, and distilled ;VOL. XCVII.7 2202 POPE AND READ : EXTERNALLY COMPENSATED TETRAHYDRO-I-Base, d-Acid.0,2118 gram in 30 C.C.h ' q ~ line). Hg(ye11ow). Hg(green).a +0*91" +0*96" +1*14"[a] +32'22 333.99 +40*37the rotatory power of the distillate is then determined, and the per-centage of d-base calculated; in general, about 80 per cent. of d-baseis present. This base is next dissolved in the requisite amount ofdilute hydrochloric acid, and to the hot solution is added ammoniumI-a-bromocamphor-r-sulphonate ; the proportion of the latter usedis about 2 per cent. less than the quantity equivalent to thed-tetrahydroquinaldine present, Crystallisation does not ordinarilyoccur spontaneously, but may be induced by inoculation with a littlecrystalline .d-tetrahydroquinaldine I-a-bromocamphor-lr-sulphonate ;the la,tter is readily obtained by evaporating a few drops of thesolution to dryness, and rubbing the residue with ether. Afterinoculation, crystallisation takes place with considerable rise intemperature, and almost the whole of the d-base separates as thesalt of the optically active acid ; the salt is purified by crystallisationfrom boiling alcohol, and its physical properties correspond withthose of the enantiorvorphously related salt.The base extracted from the final mother liquors consists mainlyof I-tetrahydroquinaldine, which may be separated by again treatingwith ammonium d-a-bromocamphor-crr-sulphonate in hydrochloricacid solution. The practically quantitative separation of theexternally compensated tetrahydroquinaldine into its optically activecomponents is thus effected.d-Base, 1-Acid.0.2034 gram in 30 C.C.H g(p el lo w) .Na ( D I in e). Hg( green 1.- 0.87" - 0 '92" - 1.05" - 32 '08 - 33 '92 - 40 '1QUINALDINE AND ITS OPTICALLY ACTIVE COMPONENTS. 2203d- Tetrahydroquinaldinne at 16'.NaD (line). Hg(ye1low). Hg(green).u +61'13" +63'66" +71*85"[u] +59+79 +62'26 +70*271- Tetiuhydroquimldine at 20'.Na(o line). Hg(yel1ow). Hg (green).- 61 '20" - 63-80" - 71.97"-60.04 -62.59 70.61d-(1-> T e t rah y dro qwinaldine d-(l-> a-Bromo carnphor-n-sulphonat e.On dissolving pure d-tetrahydroquinaldine in the equivalentquantity of d-a-bromocamphor-?r-sulphonic acid solution and7 3 2204 POPE AND READ : EXTERNA1,LY COMPENSATED TETRAHYDRO-d-Base, d-Acid.0'2143 gram in 30 C.C.1-Base, 1-Acid.0.2082 gram in 30 C.C.d- and l-Tetrahydropuinaldine Hydrochloiide, CloH~3N,HCl,H20.For comparison with the salts wit,h optically active acids, it seemeddesirable to determine the rotatory powers of the hydrochloridesprepared from pure d- and Ltetrahydroquinaldine; these salts wereprepared as already described, and recrystallised from acetone.Thefollowing determinations were made in aqueous solution in 4-dcm.tubes at 1 7 O :Hydrochloride of d-Base.Weight in 30 C.C. Na(o line).Hg(ye11ow).0*1111 gram a + 0.99" + 1-02"66-83 68.860'2004 ,, a 1 7 8 1 '8466-62 68'86a 3.64 3-78 [.I 66.33 68'88[a1r.10'4116 ,,Hg(green>. + 1 - l i "78.982'1078 -594-3178'5QUINALDINE AND ITS OPTICALLY ACTIVE COMPONENTS. 2205Eydrochloride of l-Base.Weight in 30 C.C. N ~ D line). Hg(yel1ow). Hg(green1.0'1136 grain a - 1 *01" - 1.05" - 1 *20"0.2062 ,, a 1-83 1 -90 2'18a 3 *56 3.70 4 *2366'68 69-32 79.2s66.56 69.11 79-29[a1 66.47 69.80 78.98[a11.10.4017 ,,Mean molecular rotatory powers : [MI,, 134.24" ; [M]Hg (yellow) 139.15" ;The mean rotatory dispersions are, for Hg(green)/Na(yellow) = 1.1 86,It will be seen that the values for the two hydrochlorides agreevery closely, and that the specific rotatory power decreases slowlyas the concentration increases.The mean values are appreciablyhigher than were obtained by Pope and Peachey, who found thevalue [MI, - 121-7O for Z-tetrahydroquinaldine hydrochloride indilute aqueous solution.From the values now recorded, the molecular rotatory powers ofthe optically active basic and acidic ions can be calculated for com-parison with those directly observed with the tetrahydroquinaldinehydrochlorides and the ammonium a-bromocamphor-a-sulphonatesby means of the formuh:[MI of dBdA + [MI of ZBdA =Twice [MI of dA ion.[MI of dBdA-[MI of lBdA=Twice [MI of dB ion.[M]Hg (green) 159'14".and for Hg(yelIow)/Na(J'ellow) = 1 -03 7-The following values are t h u s calculated :Basic ion. Acidic ion.Nap line).Hg(ye1low). Hg (green). Na(D line). Hg(ye11ow). Hg(:(sraen).[MI 126'4" 131.7" 152.2" I 273.8" 287.3" 337'8"Dispersions : Hg(green)/Na(yellow) = 1.203 ; Hg(green)/Nt~(ye~ow) = 1 '230 ;Hg(;(sellow)/Na(Sello\r) -- 1 '041 ; Hg(yellow)/Na(yeUow)= 1 '049.The appended values are those deduced from the examination ofthe hydrochlorides of the base and the ammonium salts of theoptically acfhe acids ;N a ( o line). Hg(:(selIow). Hggreen). Na(D he). Hg(ye1Iow). Hg(green).Dispersions : Hg(green)/Na(yellow) = 1'186 ; Hg(green)/Na(ye~ow) = 1.243 ;[MI 134.2" 139.1" 159.1" I 278.7" 295'2" 346'6"Hg(yel~ow)/Na(;(sellow)= 1 -037 ; Hg(yellow)/Nqyellow) = 1 *059.It is noteworthy that, although the molecular rotatory powersand dispersions calculated in the two different ways respectively areof the same order, the differences are much greater t'han could beattributed t o experimental errot .The discrepancies are scarcelytraceable to the disregard of the concentration of the solution2206 EXTERNALLY COMPENSATED TETRAHYDROQUINALDINE.examined, and are possibly due t,o the operation of isomeric change(compare Kipping, Trans., 1905, 87, 628); the whole question isnow being further studied.The Opticdly Active Benzoyltetrahydroq~~nald~ne~.With the aid of the pure optically active tetrahydroquinaldineswhich have been now prepared, it is possible to obtain the benzoylderivatives in a greater state of purity than previously, and to makestandard measurements of their rotation constants ; these are ofinterest because the sign of rotation of the base changes duringpreparation of the benzoyl derivative. The benzoyl derivativeswere prepared in the manner already described, and the followingdeterminations made in absolute alcoholic solution in 4-dcm.tubes :Benzoyl-d-t etrahydroquinale.Weight in 30 C.C. t. N ~ D line). Hg(yel1ow). Hg(green).0.1602 gram ......... 17" a - 7'03" - 7-40" - 8'59"0.5031 gram ......... 18 a 21.93 23-00 26 '68[a] 329.1 346-4 402.1[u] 326.9 342.9 3 9 i *7B enzo yl-1-t e t rah y dro quinaldin e .0.1751 gram ......... 17" a + 7.70" -f- 8'08" + 9'40"[u] 329.8 346.1 402.60.5067 gram ......... 18 a 22-07 23'12 26'84The agreement between the specific rotatory powers of the d- andZ-isomerides for similar concentration and identical wavelength isvery close. The mean specific rotatory powers are, for the lowerconcentration at 17O :[u] 326.7 342.2 397'3[ a l D 32 9-46' ; [a]Hg (yellow) 346.26' ; [a]Hg (green) 402.38'.The rotatory dispersions are, for Hg(green)/Na(yellow) = 1.221, andFor the higher concentration at 18O, the mean values are :The rotatory dispersions are, for Hg(green)/NZt(yellow) = 1.21 7, andfor Hg(yellow)/Na(yellow) ,= 1 '048-I n view of the obvious high order of accuracy of the above deter-minations, it can be safely concluded that the rotatory dispersionsof the benzoyl derivatives diminish slightly as the concentrationincreases, and that the rotakory dispersions of the benzoyl derivativesand those of the parent bases are not identical.for Hg(yellow)/Na(yel~ow) = 1.051.[a], 326.79' ; [a]Hg (yellow) 342.54' [a]Hg (green) 397.50'-THE CHEMICAL LABORATORY,UNIVERSITY OF CAMBRIDGE