1376
NOTES
hand Muller and Schmid6 found a rather high G-value (G = 2.6) for his-nitrosocyclohexane formed in the system. Experimental Chemicals.-Chemically pure cyclohexane was used. rjitric oxide was prepared by treating C.P. sodium nitrite with dilute sulfuric acid. The gas evolved was purified by passing i t through aqueous solutions of 90% sulfuric acid and 5OyOpotassium hydroxide. Irradiations-Irradiations were made a t 25’ using Gammacell 220, a B°Cosource of activity about 4000 curies. The dose rate in cyclohexane was 3.2 X 1017e.v./g. min. as determined by the Fricke dosimeter. The construction of Gammacell offered no possibility of changing this dose rate. The irradiations were carried out for 7-14 hours, the total dose being of the order of lozoe.v./g. Nitric oxide was bubbled through cyclohexane a t the rate 2000 ml. per hour per 800 ml. of cyclohexane. After the irradiation was finished pure nitrogen was bubbled through the reaction mixture. Analysis.-Acids were extracted from the reaction mixture by shaking with excess sodium carbonate solution and determined by potentiometric titration with hydrochloric acid. Cyclohexanone was determined by means of hydroxylamine hgdrochloride. Cyclohexanone oxime was determined colorimetrically as the yellow compound formed in the presence of ferricammonium sulfate and formaldehyde. For infrared analysis Zeiss spectrophotometer UR-10 was used.
Results I n the reaction mixture colorless crystals were always found on the walls of the reactioil vessel. Those crystals were purified by washing with diethyl ether and then recrystallized from water. The resulting product was identified as adipic acid by means of elementary analysis and determinations of the acid number and of the melting point. The acid number of the crystalline substance not recrystallized from water was 789 mg. of KOH/g. It was then higher than that of adipic acid (768 mg. of KOH). These results suggest the presence of some amounts of lower dicarbonic acids as glutaric or succinic. No considerable amounts of cyclohexanone and cyclohexanone oxime were found. The concentration of cyclohexanone in the reaction mixture was below 0.005 wt. 7 0 what corresponded G
