The Conversion of Aldonic Phenylhydrazides to Lactones

The conversion of aldonic phenylhydrazides to acids was carried out in the earlier researches by boiling with solutions of barium hydroxide. 

Some phenylhydrazides are very resistant and there is decomposition and possibly some epimerization in the alkaline solutions on long boiling. It has been found that boiling with a solution of copper sulfate is an advantageous procedure. The following directions for preparing man-nonic lactone from mannonic phenylhydrazide illustrate the method. 

One hundred grams of pure mannonic phenylhydrazide, 80 g. of copper sulfate pentahydrate, one liter of water and 1 cc. of octyl alcohol (to control foaming) were boiled for five hours under reflux. The solution was cleared of copper as sulfide, of sulfuric acid as barium sulfate, and upon concentration to 75 cc. the lactone crystallized readily. Successive crops were obtained by concentration and treatment of the sirups with methyl alcohol. The total yield of pure lactone was 55.8 g. (90%). During the reaction there is a vigorous evolution of nitrogen and in the condenser droplets of benzene appear. 

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