INVESTlGATIONS ON DEPENDENCE OF ROTATORY POWER, ETC. 267 7CCL.-Investigations on the Dependence of RotatoryPower on Chemical Constitution. Part X . TheOptical Dispersive Power of Tetrahydro-%naphtholand its Esters.By JOSEPH KENYON and ROBERT HOWSON PICKARD.IT has been shown in Parts V I and IX (this vol., pp. 1117 and2644) that the opt'ically active 1-naphthylalkylcarbinols of thegeneral formula C,,H,*CH(OH)*R have complex dispersive powersat all temperatures up to those far removed from their meltingpoints. Thus the methyl member of the series has a complex dis-persive power at,all temperatures up to about 160° and the corre-sponding a-hexyl hoinologue up t o about 180°, above which limitingtemperatures the rotations of each obey the law of simple dispersivepower a3 expressed by the Drude equation with one term,a = k / h 2 - h $ .It is further of interest to note that in the super-cooled state a t a few degrees below the melting points of thesecom p ou nd s their temper a tu re-r ot a t i on curves for so di um- y ell o w t omercury-violet light, which are perfectly regular throughout, exhibita region of so-called anomalous dispersion.It has been suggested (Zoc. cit.) that below these limiting tem-peratures the apparently homogeneous carbinols are really mixturesof two isomerides having rotatory powers of opposite sign, anddiffering in dispersive power. The further suggestion that theisomerism is due to a different disposition of the valencies in theaaphthyl radicle (the two forms being of the nature of ar- andac-derivatives) makes it desirable t o consider the dispersive powerof other compounds containing either the naphthyl radicle or otherradicle closely related to it.Already in Part 111 (T., 1912, 101, 1427) the preparation andsome of the optical properties of both dextro- and kvo-rotatoryac-tetrahydro-%naphthol have been described, but unfortunatelythe optical measu.rements were confined t o light of one wave-lengthonly.Accordingly, the work described there has been partlyrepeated, and the results confirmed and extended. It has now beenfound that the temperature-rotation curves of ac-tetrahydro-2-naphthol in the fused state from a temperature of about 120° downto its melting point at 50°, and beyond in the supercooled state to(at least) 153, are perfectly regular and smooth.The rotationsobserved in the homogeneous state up to 120°, as also in varioussolvents, obey the law of simple dispersive power, but above 120°VOL. cv. 8 BKENYON AND PICKARD : INVESTIGATIOXS ON DEPENDENCEFIG. 1.160"140"120"100"80"60"40"20"0"CHARACTERISTIC DIAGRAMforac-Tetrahydro-2-naphthol and someof its derivatives.Points marked 1 to 4 correspond with the rotations of the hydrogen phthalatea t 5 per cent. concentration in ethyl alcohol, chloroform, pyridine and benzenerespectively, points 5 and 6 with ethgl-alcoholic solutions of the sodium andpotassium salts, points 7, 9 ar.d 10 with the rotations of the valerate in thehomogenecus state a t 200", 100" and 20" respectively, and points 8 and 11 withsolutions of the valerate in chloroform and carbon disulphide.Points marked 12to 17 refer t o the rotations of the tetrahydronaphthol in the homogeneous state a t2OO", a t 140., dissolved in carbon disulphide and in chloroform, and in thehomogeneous state a t 60" and 20" respectively. It will be noticed that pointsmarked 1, 3, 5, 6 , 7 and 12 do not fit on the lines of the diagmmOF ROTATORY POWER ON CHEMICAL CONSTITIJTION. 2679the dispersive power becomes complex. Of this phenomenon theredoes not seem to be any simple explanation, but the properties ofthe reduced compound are in marked contrast t o those of the1-naphthylalkylcarbinols. The n-valeric ester in the homogeneousstate a t ZOO and in solution and the hydrogen phthalate whendissolved in benzene or chlorof o m also exhibit rotations, whichappear to conform to the law of simple dispersive power.Thevalerate, however, in the homogeneous state at higher temperatures,solutions of hydrogen phthalate in alcohol o r pyridine, and aqueousor alcoholic solutions of the sodium or potassium salt of the latterester all show complex dispersive power.The alternative method of plotting such rotations by means of a" characteristic diagram " brings out these relations in a strikingmanner. Thus the diagram (Fig. l), which is constructed in theusual manner, using the rotations for mercury-green light as areference line, only correlates those rotations of the substances justmentioned, which conform to the law of simple dispersive power.It is not surprising that the diagram fails t o correlate the rotationsof the valerate in the homogeneous state a t higher temperatures,for not only has the ac-tetrahydro-2-naphthol then a complex dis-persive power, but.also, as has been repeatedly shown, an esterifiedcarboxylic group exhibits complex dispersive power a t high tem-peratures. Assuming that dynamic isomerism is the underlyingcause of the complex dispersive power exhibited by a colourlesscompound of simple chemical constitution (containing only oneasymmetric carbon atom), i t may be stated generally that in caseswhere complex dispersive power is exhibited a t all temperatures thecompound will contain more than one possible centre of dynamicisomerism.Illustrations of this general statement can be seen inthe esters of ihe naphthylalkylcarbinols and of ac-tetrahydro-2-naphthol, whilst each of the substances mentioned above as showingcomplex dispersive power when dissolved in certain solvents con-tains, when so dissolved, two possible centres of dynamic isomerism,and the observed rotations cannot be correlated on the characteristicdiagram (Fig. 1). However, the rotations shown by aqueous SOlU-tions at various concentrations of sodium ac-tetrahydro-2-naphthylphthalate can be correlated oli another diagram (Fig. 2) speciallydrawn for these, and permit the inference that there is some relationbetween them.Attention has already been drawn in this series of investigationst o the danger of basing conclusions on the values of any one disper-sion ratio.A good example of this danger is to be seen in thedispersion ratios of the1 substances named in tables I and 11. Itwill be noted that in the homogeneous state the ratio f o r mercury-8 M 2680 KENYON AND PICKARD : INVESTIGATIONS ON DEPENDENCEvioletlgreen remains constant, but that for mercury-violet/sodium-yellow tends constantly to increase. This is well brought out inthe diagram (Fig. l), where' the lines for violet, green and yellowFIG. 8.4"3"s 9 2"&$ 32&h0 1"0"- 1"- 29CHARACTERISTIC DIAGRAMforphthalate in aqueous solutions.(1) 2.0 per cent. solution(4) 8.0 .,Sodium 2-ae-tet ra hyd ro-2-napht hyl(594.2 ,)(3) 6 1 wintersect a t zero.When the green is used as a reference line therotation values for violet and green all lie approximately on thetwo lines, so that the dispersion ratio is constanti, but in the caseswhere complex dispersive power (see, for example, points markeTemp.20"40608010012014016018020020'406080100120140160180Density.D .1.09101.07501.05901.04311.02751.01210-99550.97900.96300-94701.02841.01400.99950-98530.97090.95650.94210,92760.9133[a]",-!- 75.68"71.8568.3565-3662-6659.9457-5055.2652.9650.86- 46.80"45.7744.7143.6242-4841-3040.0538-7937.43TABLE I.R o tat ory Powers u t Di ff ere n t Temperad-ac-Te tra hydro-2-vaapht hol.ial",.+ 90.26"86.7282.6279.1675.3972.3369.8267.3664.6662-47[a]:i.155.51148.98142.05135.65130.13125.88121.04116.10112.15$162.16' -+ [MIL.. 112.0"106.4101.296.792.688.785.181.878.475.3[MI:,.+ 133.6'128.3122-117.1111.6107.0103.499.795.792.51-ac-Te tra hydro-2-naphthyl n-Valerat-56.23" -55-3454.4353.5052.5251.5450.5649.5348.45.99-97" -98.4096.7495.1393.4091-6089.8087.9685.96108.6" -106.2103.7101.298.695.892.990.086.8130.5"128.3126.3124.1121.8119.6117.3114.9112.Length of Weightobserva-Solvent.Pyridine . . . . . .Ethyl alcoholChloroform . . .Carbondisulphide . .Benzene . . . . . .Chloroform . ..Ethyl alcoholEthyl alcoholChloroform . . .Pyridine . . . . . .Benzene . . . . . .Ethyl alcoholtiontube,cm.222022202022222222222222TABLE 11.d-ac-Tetra hydro-2-wpht hol.1.0163 + 8.49' + 10.23' + 18.40' +75.97" +91*54O + 164.6'1.0313 7.79 9.37 16.63 75-56 90.88 161.40.9968 7.38 8.85 15.70 67.32 80.71 143.21.0206 6.36 7.67 13.71 62.30 75.13 134.30.9653 5.95 7-14 12-70 61.50 73.98 131.6d-ac-Tetrahydro-2-mphthyl Hydrogen Phthalate.1.0718 +1*60 +1.89 +3.40 +13*67 +16.03 +28.84Brzscine Salt of the &Ester.1.0621 +@48 +0*25 -1.05 +4.11 f2.14 -8.99l-ac-Tetrahydro-2-6upht hyl H?/droyen Pht0.9830 -1.05 -1.22 -1.85 -9.72 -11.28 -17.1 11.0212 1.54 1.94 3.31 13.71 17-27 29-401.0597 1.85 2.33 3.99 15.87 19.99 34 2 30.4423 1.34 1.62 2.90 27.54 :{3.30 5 ~ 6Cinchonidine Salt of the I-F, / Y fi er.1.1052 -8.81 -11.03 -19.72 -72.46 -90.74 -102.20The solutions for the observations of rotatory power recorded in tables I1 and 111 were preparedsolute to 20 C.C.with the solvent a t the temperature of the laboratory, at whicLength ofobservationtube,Solvent. cm.Water .................. 22 ,, .................. 22,, .................. 22,, .................. 22Ethyl alcohol ...... 22Chloroform ......... 22Ethyl alcohol ...... 20Benzene ............. 20Carbondisulphide ......... 20TABLE 111.Sodium. 1-a c-Tetra.h ydro-2-napht hyl Phthalate.Weightofsolute,grams.0.51 171.03321.52801-96600.94230.98671.00670.82791.0292a,. agr.avi. [a]wf O o +0-04' +0.26' +O" ++_O +()a07 +0*45 +_O +-0.17 -0.14 +0*15 -1.24 --0.45 -0.48 -0.44 -2.54 --1.53 -1.83 -2.91 -18.05 -21.591-a-Tetrahydro-2-naphthyl n- Falerate.-4.45 -6.38 -9.48 -41.01 -49.57-4.15 -4.98 -8.91 -41.21 -49.45-4.44 -5.35 -9.53 -53.63 -64.63-6.57 -7.96 -14.40 -63.86 -77.3affords a much better method of purifying the' ac-compound thanthe older one.This sodium salt crystallises from water in long needles, or fromaqueous alcohol in large tablets, has the compositionCO,Na*C,H,*CO,* C,,H,,, 4H20,eflloresces a t about 60°, does not melt below 200°, and is verysoluble in ethyl alcohol :Na = 5-88.0.3218 lost 0.0582 H,O and gave 0.0584 Na,SO,. H20=18*23;C,8H,,0,Na,4H,0 requires H,O = 18.23 ; Na = 5-88 per cent'.The resolution of the 6Z-hydrogen phthalate was carried out inthe manner already described (Zoc.cit.), and the results were con-firmed. The d- and 1-est'ers form sodium salts, which have similarproperties to that of the' 61-ester.Determi?iations of Rotatory Power (u100mm.) of the Carbin02 awJl-ac-Tetrah ydro-2-izaphthyZ n-?'-alerate in the Homogeneous State.d-ac-l'e trahydro-2-naphthol.Temp. 28.5' 65"a,, ...... +80.50" 71.20" (see also Part III., loc. &.).Temp. 27" 59" 82" 126" 136" 156" 180'a,, ... +96*72' 88.54' 82.00" 71.72' 70.58' 66.88" 62.26'Temp. 26.5" 58' 84' 126' 137" 157' 180'a y t . . . . . . + 173.60" 158.80" 146.04" 129.64" 126.30' 119.70" 111.80'* When not otherwise stated, the experimental procedure is similar to thatpreviously described (Zoc. cit.)KENNER : THE HEDUCTlON PRODUCTS, ETC. 2685l-ac-Te t~niiydro-2-?iapJ~th y l n- Valeya t e.*Temp. 20" 44" 54" 110" 135" 161"a=...... -48.12" 46.24" 45.64" 40.16" 38-36' 35.80"Temp. 20" 43; 6 9 O 110" 138" 160"agr ... -557.80" 55.86" 54.44" 50.22" 47-84' -446.00"Temp. 20" 41" 59" 110" 136" 162"ari . . . - 102.78" - 99.90" - 96-52' - 89.60" - 85.00" - 81.20"The authors desire to express their thanks to the GovernmentGrant Committee of the Royal Society for a grant, which hasdefrayed some of ths expense of this investigation.MUNICIPAL TEOHNICAL SCHOOL,BLACKBURN