STUDY OF THE EFFECT OF THE REAGENT RATIO ON THE REDUCTION OF ACETYLDIPHENYL WITH ALUMINUM ISOPROPOXIDE

V. L. Ivasenko, E. E. Sirotkina, V. P. Lopatinsky

(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)

In a previous communication, results were presented from a study of the effect of temperature on the reduction of acetyldiphenyl. For a more detailed investigation of the reduction of acetyldiphenyl with aluminum isopropoxide in a p-xylene medium, we studied the effect of changing the ratio of aluminum isopropoxide to acetyldiphenyl on the yield of phenylstyrene and on the reaction order, since it is known that the reduction of aliphatic-aromatic ketones may proceed by a reaction having a fractional order that varies depending on the reagent ratio [1, 2].

The reduction process was studied at ratios of acetyldiphenyl to aluminum isopropoxide of 1 : 1, 1 : 3, and 1 : 6, at a temperature of 100°C. The reduction procedure is given in work [2]. The concentration of acetyldiphenyl during the reduction process was measured polarographically according to the method developed by V. D. Bezugly [3]. The change in the concentration of aluminum isopropoxide during the reduction process was determined by calculation, based on the fact that, in the reduction of aliphatic-aromatic ketones with aluminum isopropoxide in an aromatic-hydrocarbon medium, one mole of aluminum isopropoxide is consumed for the reduction of one mole of ketone [2]. The concentration of carbinol was determined by the method given in work [4]. The yield of phenylstyrene and of its polymer was determined from the difference between the amount of ketone that had reacted and the carbinol formed, since part of the phenylstyrene polymerizes during the reduction process. The reaction order with respect to aluminum isopropoxide was determined by the method recommended by Yatsimirsky [5].

The results of the investigations are presented in the figure.

From the data presented it is evident that, with an increase in the ratio of aluminum isopropoxide to acetyldiphenyl, the yield of phenylstyrene increases and that, with a decrease in the concentration of aluminum isopropoxide, the reaction order decreases. The reduction of acetyldiphenyl with aluminum isopropoxide in an aromatic-hydrocarbon medium probably proceeds by two parallel reactions, one of which is first order and the other second order with respect to aluminum isopropoxide; moreover, the principal amount of phenylstyrene is formed by the reaction having an overall third order. Phenylstyrene may also be formed in part as a result of dehydration of the carbinol, which is formed by a reaction having an overall second order.

Fig. 1. Effect of the ratio “acetyldiphenyl : aluminum isopropoxide” on the yield of phenylstyrol and on the reaction order at a temperature of 100°C.

— reaction order;
△ — concentration of acetyldiphenyl;
× — concentration of carbinol;
○ — concentration of phenylstyrol.

Conclusions

1. The effect of the reagent ratio on the yield of phenylstyrol and on the reaction order in the reduction of acetyldiphenyl with aluminum isopropoxide in an m-xylene medium was studied.

2. It was shown that, as the ratio of aluminum isopropoxide to acetyldiphenyl increases, the yield of phenylstyrol increases.

3. It was shown that, as the concentration of aluminum isopropoxide decreases, the reaction order decreases.

References

1. W. N. Moulton, R. E. Van Atta. J. Org. Chem. 26, 290 (1961).

2. V. L. Ivashko, E. E. Sirotkina, V. P. Lopatinshchii et al. Reduction of Certain Aromatic Compounds with Aluminum Isopropoxide. Izvestiya TPI, 185, 1970.

3. V. D. Bezuglyi. Polarography in the Chemistry and Technology of Polymers. Publishing House of Kharkov State University, Kharkov, 1964.

4. I. Guben-Weyl. Methods of Organic Chemistry, Vol. II, Goskhimizdat, Moscow, 1963.

5. K. B. Yatsimirskii. Kinetic Methods of Analysis, Khimiya Publishing House, Moscow, 1967.