The following density determinations were made, d 40°/4° 1.1725; d 50°/4° 1.1617; d 60°/4° 1.1509, = and the following polarimetric observations. Rotation of methylic paratoluylmalate. Observed rotation aD in 999 mm. tube. = Density compared Temperature. 18.5° The results recorded above may be summarised as follows. 1. The lavorotation of ethylic is greater than that of methylic malate. 2. The lavorotation of ethylic malate is diminished by the introduction of the benzoyl and three toluyl groups. The lavorotation of methylic malate is also diminished by the introduction of the benzoyl, paratoluyl, and metatoluyl groups, but is increased by the introduction of the orthotoluyl group. The exceptional influence of the orthotoluyl group on methylic malate will be discussed later, the uniform effect in the other cases of the substitution is to depress the lævorotation, or, in other words, to exert a dextrorotatory, influence. 3. At the ordinary temperature (20°), the dextrorotatory influence of these groups follows in the order paratoluyl > benzoyl > metatoluyl > orthotoluyl both for methylic and ethylic malate. 4. At a high temperature (136°), on the other hand, the sequence of the dextrorotatory influences of these groups is paratoluyl > metatoluyl > benzoyl > orthotoluyl in the case of methylic malate, and paratoluyl > metatoluyl > {orthotoluyl) which are prac- in the case of ethylic malate. tically identical Thus it will be seen from the diagram on p. 346 that the specific rotation curve for methylic benzoylmalate cuts that for methylic metatoluylmalate at a temperature of about 120°, and that the specific rotation curve for ethylic benzoylmalate cuts that for ethylic metatoluylmalate at about 95°, and that for ethylic orthotoluylmalate at about 132°. Again, it will be seen that the influences of the benzoyl, metatoluyl, and orthotoluyl groups become almost identical at the high Specific Rotation of Methylic and Ethylic Salts of Benzoyl and Toluyl (o, m, and p) Malic Acid. 0 20. 30. 40. 50. 60. 70. 80. 90. 100. 110. 120. 130. 140. Temperature in Degrees Centigrade. temperature (136°), both in the case of ethylic and methylic malate respectively. 5. At the ordinary temperature (20°), the rotatory influences of the several groups are as follows. Methylic malate Benzoyl dextrorotatory Λ Orthotoluyl Metatoluyl Paratoluyl Methylic malate Ethylic malate dextrorotatory Thus in all cases the dextrorotatory influence of the aromatic group is greater on the ethylic than on the methylic compound, indeed the orthotoluyl group, whilst exerting a dextrorotatory influence on ethylic malate, exerts a lævorotatory influence on methylic malate. 6. At a high temperature (136°), on the other hand, the rotatory influences of the several groups are as follows. Thus, again, the dextrorotatory influence of the aromatic group is more pronounced on the ethylic than on the methylic compound; indeed, at the high temperature the influence of all four aromatic groups is actually lævorotatory on methylic malate, whilst the paratoluyl group at any rate has still a dextrorotatory influence on ethylic malate. MASON UNIVERSITY COLLEGE, XXXIV. Some Regularities in the Rotatory Power of Homologous Series of Optically Active Compounds. By PERCY FRANKLAND, Ph.D., F.R.S. IT is difficult to find a consistent explanation for the phenomena to which attention has been drawn in the preceding paper, the lower lævorotation of the substituted ethylic malates being particularly perplexing when it is borne in mind that the lævorotation of methylic malate is lower than that of ethylic malate. Thus it would be anticipated that the dextrorotatory influence of the aromatic acidyl group should depress the lavorotation of both methylic and ethylic malates, and that the methyl compound should have a smaller lævo rotation than the ethyl compound, whilst, as a matter of fact, the reverse is actually the case. The following explanation is provisionally suggested to account for the facts. The experimental specific rotations of methylic and ethylic malates are not the specific rotations of monomolecular bodies; both of these ethereal salts are associated, and the methyl compound is more highly associated than the ethyl compound. This association leads to a lower negative specific rotation than is possessed by the monomolecular substances, and of the latter the methylic has a higher negative rotation than the ethylic. On introducing the acid radicles, the molecules become simple or more nearly so, and the dextrorotatory influence which they exercise depresses the negative rotation of both methylic and ethylic malate, the negative rotation of the methylic naturally remaining greater than that of the ethylic compound. This explanation is also in general harmony with the results obtained by Walden (Zeit. physikal. Chem., 1895, 17, 245-266) in the case of other derivatives of malic acid. Thus, Dimethylic acetylmalate -22-92° propionylmalate - 22.94° butyrylmalate - 22'44° * Walden has shown that the chlorosuccinates really corresponding with the ordinary malates have the same lavorotations (Ber., 1896, 29, 133). In the case of all these substituted malates, the substitution raises the lavorotation, and in each substituted series, excepting that of bromacetylmalic acid, the methylic has a higher rotation than the ethylic compound. The following evidence of the association or otherwise of the several compounds referred to in the previous paper is afforded by Traube's formula for the calculation of molecular volume.* *The calculated molecular volumes given in this paper have been obtained by using the formula Vm = m9′9C + n3·1H + p2·30′ + q5′50′′ + 259, in which 0 = atomic volume of hydroxylic oxygen. The value for O' becomes 0'4 when OH is attached to a carbon atom which is also doubly linked to an atom of oxygen (carboxyl group) or when the neighbouring carbon atom is also attached to an OHgroup, as in the ethereal salts of tartaric acid. " = atomic volume of oxygen when doubly linked to carbon (either to one or to two carbon atoms). 25'9 = "Covolume." 13.2 is deducted for each benzene ring present in the molecule (Ber., 1895, 28, 2724). Atomic volume of Cl = 13.2 In my paper in conjunction with Dr. McCrae (Trans., 1898, 73, 324), on some of the monacidyl derivatives of ethylic tartrate, the values employed were taken from an earlier communication of Traube's, and these led to a wider divergence between the calculated and experimental molecular volumes than when the above more recent figures are used in calculation. Thus |