-- and 10.34° (c=551). The rotation of the methoxy-acid, like that of its homologue, is raised by alcohol. The following observations show that the rotation of calcium ethoxypropionate falls with rise of temperature, and that its behaviour therefore is not in accordance with the general rule, that rise of temperature and dilution produce similar effects. p=24·434, d 10°/4° 1.0993, [a] = -37.75° = To the distinctive points in the optical behaviour of lactic and the alkyloxypropionic acids previously indicated (Trans., 1898, 73, 877 ; 1899, 75, 160), we may now add the phenomena exhibited by the zinc and magnesium salts. A N/10 solution of zinc lactate, despite its comparatively slight electrolytic dissociation, gives a rotation which is not much short of the maximum rotation of the alkali salts; the rotations of the zinc alkyloxypropionates at similar concentration, though increasing rapidly, are still far short of the maximum. The molecular rotations of the lactates of the zinc group increase with molecular weight; the converse nolds true for the alkyloxypropionates. UNITED COLLEGE OF ST. SALVATOR AND ST. LEONARD, XLVII.-Position-Isomerism and Optical Activity. The Comparative Rotatory Powers of Methylic and Ethylic Ditoluylglycerates. By PERCY FRANKLAND, F.R.S., and HENRY ASTON, Late Priestley and Forster Scholar in Mason University College, Birmingham. THE influence of position-isomerism in the benzene ring on the rotatory power of optically active substances has formed the subject of several previous investigations by one of us, as well as by other workers (for summary of results in this connection, see P. Frankland and McCrae, Trans., 1898, 73, 307; also P. Frankland and Wharton, Trans., 1896, 69, 1309, 1583; 1899, 75, 337). The present paper deals with the preparation and rotatory properties of the methylic and ethylic salts of the three isomeric ditoluylglyceric acids, which are also compared with the methylic and ethylic salts of dibenzoylglyceric acid. previously prepared by P. Frankland and MacGregor (Trans., 1896, 69, 104). The ethereal salts in question were respectively prepared by the action of the three isomeric toluic chlorides on methylic and VOL. LXXV. L L ethylic glycerates. The toluic chlorides were all prepared by the action of phosphorus trichloride at 120-170° on the corresponding toluic acids; they had the following properties: Paratoluic chloride (from paratoluic acid, m. p. 178.3°), boiled at 102° under 15 mm. pressure in one preparation, and at 108° under 15 mm. pressure in a second, in which the boiling point was taken in a different flask and with another gauge. Orthotoluic chloride (from orthotoluic acid, m. p. 102°), boiled at 99-100° under 14 mm. pressure in one preparation, and at 103° in another, in which a different flask and gauge were employed. Metatoluic chloride (from metatoluic acid, m. p. 109.5—110°), boiled at 109° under 15 mm. pressure. Methylic Diparatoluylglycerate (Inactive). Inactive methylic glycerate (15 grams) was gradually added to twice the calculated quantity of paratoluic chloride (78 grams) at 120-150°. After removing excess of acid chloride by distillation, the residue was dissolved in ether and washed with an aqueous solution of sodium carbonate. The ethereal solution, after drying with calcium chloride, was allowed to evaporate. The resulting crystals were dissolved in benzene, precipitated with light petroleum, and exhibited a final melting point of 98°. I. 0-2068 gave 0·5116 CO2 and 0·1033 H2O. C= 67·47; H=5·55. The following density determinations were made :— d 99.5°/4° 1·1170; d 116°/4° 1·1055; d 134°/4° = 1.0915. Methylic Diparatoluylglycerate (Active). = This was prepared from active methylic glycerate (a, 6·06, 7 = 1) in the same manner as described above for the inactive compound. The final melting point of the crystalline product was 102°. I. 0·2007 gave 0·4964 CO2 and 0·0993 H2O. C= 67·45; H=5·49. II. 0.2077 0.5133 CO2 0.1018 H2O. C 67.40; H=5.44. = C20H2006 requires C=67.42; H=562 per cent. The density determinations gave: d 77°/4° = 1·1411; d 99°/4° = 1·1193; d 117°/4° = 1·1032; Ethylic Diparatoluylglycerate (Active). This was similarly prepared to the methylic compound. Precipitation from benzene by light petroleum, however, only gave the substance as an oil; but on dissolving the latter in alcohol, it was obtained crystalline. The final melting point was 69°. I. 0·2010 gave 0·5022 CO2 and 0·1055 H2O. C=68·14; H=5·83. The density determinations gave: = = d 66°/4° 1.1239; d 84°/4° 1.1076; d 100°/4° -1.0952; = Methylic Dimetatoluylglycerate (Active). The method of preparation was similar to that described above. On precipitating the benzene solution with light petroleum, the substance was obtained as an oil, which could not be induced to solidify. The process of dissolving in benzene and precipitating with light petroleum was repeated until the product had a constant rotation. C=67·31; H=5·51. I. 0.2040 gave 0·5035 CO2 and 0·1012 H2O. The density determinations gave: = d 58°/4° 1.1663; d 74.7°/4° 1.1495; d 99.8°/4° 1.1264; = Ethylic Dimetatoluylglycerate (Active). The preparation was similar to that of the methylic compound, and, ike the latter, it could not be induced to crystallise. I. 0.2073 gave 0·5171 CO2 and 0·1089 H2O. C=68·03; H=5·83. II. 0.2053 0-5125 CO2 0.1081 H2O. C=68.08; H=5.85. C2H22O6 requires C 68.11; H=5.95 per cent. 21 = The density determinations gave: d 56°/4° 1.1436; d 70·8°/4° = 1·1300; d 98·4°/4° = 1∙1060; = Methylic Diorthotoluylglycerate (Active). The mode of preparation was similar to that adopted in the case of the meta-compound. It was only obtainable as an oil possessing a slight yellow colour, which boiling in alcoholic solution with animal charcoal failed to remove. C20H2006 requires C= 67-42; H=5.62. per cent. The density determinations gave: d 58.2°/4° = 1·1773; d 72°/4° = 1∙1659; d 98°/4° = 1·1404 ; and the following polarimetric observations were made: Ethylic Diorthotoluylglycerate (Active). This was prepared in the same way as the meta-compound, and, like it, could only be obtained as a nearly colourless oil. I. 0.2000 gave 0·4995 CO, and 0·1037 H2O. C-68·11; H=5·76. 21 The density determinations gave: d 61°/4° = 1·1562; d 77°/4° = 1·1421; d 98·7°/4° = 1·1217; and the following polarimetric observations were made : Rotation of ethylic diorthotoluylglycerate. A comparison between these values and th ose previously obtained by one of us (Trans., 1896, 69, 106 and 108) for methylic dibenzoyl |
