When N -phenylsydnone is hydrolyzed by acid, an internal oxidation- reduction reaction takes place with the formation of phenylhydrazine, formic acid, and carbon dioxide. The mechanism shown below was suggested for this reaction by Baker and Ollis. Aside from the nature of the end products of this hydrolysis, the strongest evidence cited by Baker and Ollis in support of their mechanism is the paper by Kenner and Mackay who reported the isolation of a-acylhydrazines when the hydrolysis was carried out in benzene with stoichiometric quantities of water and hydrochloric acid. However, Kenner and Mackay gave no experimental evidence to support their conclusions and others have not been successful in repeating this work
Staley, Joanne and Clarke, Donald Dudley PhD, "Acid hydrolysis of 3-phenylsydnone-2-N15 / Joanne Staley and Donald D. Clarke Chemistry Department, Fordham University, Bronx, New York" (1964). Chemistry Faculty Publications. 37.