Reactions Caused by Activated Alumina

Abstract

WE have observed that passage of a chloroform solution of diacetyltoxicarol through alumina activated for chromatographic adsorption causes hydrolysis ; in one experiment, 1.1 gm. of pure toxicarol was isolated from 2 gm. of ester. Of the two acetoxy groups attacked, one was derived from a phenolic, the other from an enolic hydroxyl group ; both are very readily hydrolysed by alcoholic alkali. This hydrolysis, which is the more remarkable in that it occurred in a non-polar solvent, was traced to the alkalinity of the alumina used. Commercial activated alumina in water reacts alkaline to phenol-phthalein and the alkalinity can be titrated with sulphuric acid ; the colour returns if the mixture is kept after neutralization ; further quantities of acid are consumed after six and again after eighteen hours ; thereafter the supernatant solution remains colourless. The following figures are for 5 gm. of (1) Merck's alumina for adsorption, activated according to Brockmann, (2) B.D.H. aluminium oxide for adsorption purposes, (3) B.D.H. aluminium oxide, calcined, and (4) B.D.H. aluminium oxide (calcined) AnalaR, shaken in 50 c.c. of distilled water.