The decomposition by oxygen-free saturated lime-water at 25" of lactose into galactose and a-and p-isosaccharinic acids has been studied. Its mechanism is interpreted in terms of the behaviour of P-alkoxy-carbonyl compounds.IT was concluded in Part I * that analogy with a-alkoxy-ketones suffices to explain the reducing properties of many forms of oxycelluloses but not their sensitivity at the ordinary temperature to weak alkali. Now, in an anhydroglucose unit (I) of cellulose replacement of any of the alcohol groups by a carbonyl group leads to a structure which in relation to the adjoining anhydroglucose units of the chain can be regarded not only as an a-but also as a p-alkoxycarbonyl compound, and in this and subsequent papers we shall adduce evidence of the merits of the latter comparison. Although the behaviour of p-alkoxycarbonyl derivatives towards alkali has not been systematically studied, the formation of ap-unsaturated carbonyl systems from p-hydroxy-and P-nitrosamino-carbonyl derivatives (Jones and Kenner, J., 1933, 363, Adamson and Kenner, J., 1934, 838), and the reversal of the Michael reaction (Ingold and Powell, J., 1921, 1976) are familiar. Closer to our theme is the formation of tetraethyl propane-1 : 1 : 3 : 3-tetracarboxylate by interaction of chlorodimethyl ether with ethyl sodiomalonate (Simonsen, J., 1908, 93, 1777) and of crotononitrile by the action of ethylmagnesium iodide on p-methoxybutyronitrile (Bruylants and Mathus, BUZZ. Acad. YO^. BeZg., 1926,11, 637), and Head has recorded the rapid formation of glyoxal by the action of cold dilute aqueous sodium carbonate on the periodate oxidation product (11) of p-methylcellobioside but not from that of p-methyl-* Part I, preceding paper. that of the p-alkoxycarbonyl system by Nicolet ( J . A m y . Chem. Soc., 1931, 53, 4458) and, with particular reference to oxycelluloses, by Haskins and Hogsed ( J . Org. Chem., 1950Chem., , 15, 1264. Much earlier Kiliani and his collaborators (Ber., 1909, 42, 2603, 3903, and earlier papers) had obtained isosaccharinic acid from lactose by the action of lime-water at and above room temperature. Further, it should be realised that acceptance of the mechanism here developed involves rejection of that put forward by Evans (Chem. Reviews, 1942, 31, 537).Meanwhile, it appears permissible to interpret the decomposition of carbonyl oxycelluloses along similar lines. Thus, in the case of a 2-carbonyl group in an anhydroglucose unit (VII) of the cellulose chain we have : qH,*OH CH,.OH CH,*OH (VII) (R and R' = anhydroglucose chains) I CO,H EXPERIMENTAL Determimztion of the Degradation Products.-A solution (100 ml.) of " AnalaR " lactose (0-8675 g.) in saturated oxygen-free lime-water (0.0386~) was kept at 25". A t intervals
