First-order rate coefficients a t three temperatures, and energies and entropies of activation, have been determined for the acid-catalyzed hydrolysis of methyl glucopyranosides containing various substituents a t C-5 and for glycopyranosiduronic acids with different aglycones. Substitution a t C-5 increased the stability towards acids of methyl a-and P-D-glucopyranosides, but there was no correlation between either the polarity or the size of the substituent and the rates of hydrolysis. The operation of either an inductive or a coilformational effect alone was accordingly deemed unlikely.Methyl a-and 0-D-glucopyranosiduronic acids and methyl a-D-galactopyranosiduronic acid were only slightly more stable towards acids than the glycoside analogs, while benzyl 0-Dglucopyranosiduronic acid was three times more stable. T h e presence of a methyl ester group a t the carboxyl function increased the stability of the glycuronide bond. Isopropyl, n-butyl, isobutyl, and neopentyl P-D-glucopyranosiduronic acids were hydrolyzed approximately twice and cyclohexyl 0-D-glucopyranosiduronic acid five times as fast as the corresponding glucosides. This appears to be the first time that glycuronides have been found to be hydrolyzed by dilute acid a t a higher rate than their glycoside analogs.The energies and, especially, the entropies of activation were, throughout, lower for the glycuronides than for the glycosides. The difference in entropy suggests that the two classes of compounds are hydrolyzed by different mechanisms.

the solution boiled for 2 hours. Iodine was evolved immediately and deposited on the surface of the condensing tube. After cooling and diluting with water, the iodine was reduced by addition of sulphur dioxide solution, when we obtained a clear pale yellow solution. This was finally concentrated, decolorized with charcoal, and cooled. Beautiful, colorless prisms deposited, which did not melt below 300'. The compound was identified as z,6-dioxypyrimidine-5-acetic acid. The yield was nearly quantitative. A mixture of this and thymine melted below 260'. The compound contained no halogen, was soluble in alkali, and was precipitated from its alkaline solution by addition of acids. When the above mother liquor (HI solution) was digested with an excess of sodium hydroxide, ammonia was evolved, showing the presence of ammonium iodide in the solution. Analysis (Kjeldahl) : Calculated for C,H,O,N,: N, 16 47. Found N, 16 44 z,6-Dioxypyrimidine is not reduced a t the double bond in the 4,5-One-half a gram of the acid There was no colora-This stability positions by the action of hydriodic acid. was recovered unaltered after digestion for 3 hours. tion of the acid, due to the formation of any free iodine. of the unsaturated ring, in presence of hydriodic acid, is remarkable. N E W HAVEN, CONN [CONTRIBTTION FROM THE CHEMIC4L LABORATORY OF THE UNIVERSITY OF ILLINOIS.] METHYL PHENYLIMINOMALONATE AND ITS REACTIONS.

No abstract