XXIX.—The action of alkyl iodides on silver malate and on silver lactate

Thomas Purdie, G. Druce Lander
1898 Journal of the Chemical Society Transactions  
THE silver salts of organic acids react, as a rule, very readily and completely with the lower alkyl iodichs, and as the chemical chwge usually follows a perfectly normal course, it affords, as is well known, one of the most trustworthy processes for the preparation of ethereal salts, furnishing a pure product and a satisfactory yield in many cases where the commoner processes of etherificationcannot be employed. The method obviously recommends itself for the preparation of the ethereal salts
more » ... he ethereal salts of optically active acids which are liable to have their activity impaired by the action of mineral acids ; for this reason, it was employed in the preparation of the active ethereal alkyloxy-succinates (Trans., 1895, 67, 970), and it gave satisfactory results. I n applying the method, however, to hydroxy-acids, we find that the reaction does not proceed entirely in the normal direction, and that it cannot be relied ou to produce the ethereal salts of such acids in a state of purity. J. Wallace Walker (Trans., 1895,67,916) prepared ethereal lactates from the silver salt and found them to be more active than specimens prepared by other investigators by the commoner methods. This result suggested a research on the optical activity of ethereal malates and lactates prepared by different methods (Purdie and Williamson, Trans., 1896, 69,818), which showed that in general the ethereal salts obtained by the action of primary iodides on the silver salts did, in fact, exhibit a considerably higher activity than those prepared with the aid of hydrochloric or sulphuric acid, the difference amounting in some cases t o about 20 per cent. of the total activity. The reaction in these cases appeared, nevertheless, to run its normal course ; the results of analysis, the nearly constant boiling points of the products, the yield obtained, and the comparative constancy of the activity of different preparations seemed to preclude the idea that the ethereal salts could be contaminated with substances of higher activity. The obvious alternative explanation, that the lower activity of the ethereal salts made by the commoner methods might be due t o racemisation, was not supported by experiment, as racemic compounds could not be detected in the products of hydrolysis in such quantity as would account for the defect in activity. No explanation of the apparent anomaly could be given. I n attempting to prepare isopropylic malate (Zoc. cit.), it was found that the action of isopropylic iodide on silver malate was quite abnormal. The yield of ethereal salt obtained was very small, the activity of different preparations varied considerably, and was nearly two and a half times as great as that of normal propylic malate, an n 2
doi:10.1039/ct8987300287 fatcat:clmwfsx7d5hq3idxirep6jxdtu