H.-J. Buschmann et al.: The Reversible Hydration of Carbonyl Compounds in Aqueous Solution, Part I 41 T h e same is true with respect to the theoretical approach concerning the stability of W/O microemulsions within the validity range of this model (wo > 20). The surprising validity of the applied equipartition principle as concluded from the excellent coincidence between measured and calculated points, appears noteworthy. T h e latter observation certainly points to a remarkable monodispersity of the discussed W/O microemulsions.The equilibrium constants of hydration (given in parenthesis) have been determined for the aliphatic aldehydes acetaldehyde (1.2), propionaldehyde (1.24), butyraldehyde (0.58), pentanal (0.34), and hexanal (0.41), for the halogenated acetones chloracetone (0.091), fluoroacetone (0.167), and l,l,l-trifluoroacetone (35), and for the 1,2-dicarbonyl compounds 2.3-butanedione (2.1) and 2,3-pentanedione (1.7). Comparing the constants shows, that the equilibrium of hydration of carbonyl compounds is determined mainly by the inductive effects of the substituents.Die Hydratations-Gleichgewichtskonstanten (in Klammern angegeben) wurden fiir die aliphatischen Aldehyde Acetaldehyd (1,2), Propionaldehyd (1,24), Butyraldehyd (0,58), Pentanal (0,34) und Hexanal (0,41), fur die halogenierten Acetone Chloraceton (0.091), Fluoraceton (0,167) und 1,l,l-Trifluoraceton (35) und fur die 1,2-Dicarbonylverbindungen 2,3-Butandion (2,l) und 2.3-Pentandion (1,7) bestimmt. EinVergleich der Konstanten zeigt, daD das Hydratationsgleichgewicht von Carbonylverbindungen vorwiegend durch den induktiven Effekt der Substituenten bestimmt wird. 0 OD 11 I I 00 KI J I + O i O c CHI-CH~--C-C-CHI .J i 1 i , , , , , 483 280 2.33 185 1MA 28, 162 (1974).Czech. Chem. Commun. 31, 388 (1966).

is removed in a vacuum and the residue is taken up in 200 ml of 0.1 % aqueous hydrocyanic acid and added t o a column (40 mm diameter by 100 mm) of carboxymethylcellulose.Most of the unchanged cyanocobinamide runs through the column; the rest is eluted with 2 % acetic acid, and immediately thereafter the cobyric ester (3) of 1-aminopropan-2-01 is eluted with a 1 : l mixture of 2 % acetic acid and 2 % ammonium acetate solution. This ester is purified by extraction with phenol[3J, taken up in 100 ml of water, and acetylated by slow, dropwise addition to 5 ml of acetic anhydride at 0 to 2°C with stirring. After an hour the product is washed twice with 10 ml of chloroform, and the corrinoid is purified by extraction with phenol. For cleavage, the ester is kept at 0°C for 2 h in 200 ml of 1 M aqueous piperidine solution. The mixture is washed three times with 30 ml of 2:1 isopropyl ether/l-butanol and brought to p H 5.5 by dilute hydrochloric acid. After a further phenol extraction and cellulose-column-chromatography with sec-butanoli water (10: 3) the cobyric acid is obtained in pure form; yield 20-22 %.