Reactivities of mixed organozinc and mixed organocopper reagents. Part 13 Kinetic study for phosphine‐catalyzed acylation of alkylarylzincs and effect of residual group on the transfer rate of alkyl group |
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Authors: | Özgen Ömür Pekel |
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Institution: | Ankara University, Science Faculty, Ankara, Turkey |
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Abstract: | Kinetics of reactions of di‐n‐butylzinc, n‐Bu2Zn, and mixed n‐butyl(substituted phenyl)zinc reagents and n‐Bu(functional group (FG)?C6H4)Zn with benzoyl chloride in the presence of tri‐n‐butylphosphine have been investigated. Reaction rates of transferable n‐butyl group have been determined in tetrahydrofuran at 0 °C to compare the transfer rate of n‐butyl group in homo and mixed diorganozincs. Rate law is consistent with a third‐order reaction, which is first order in diorganozinc, benzoyl chloride, and n‐Bu3P, and a mechanism was proposed. The lower reaction rate of n‐BuPhZn than that of n‐Bu2Zn and negative reaction constant in Hammett plot are in accordance with the carbanionic charge of transferable n‐butyl group in the acylation reaction. These findings support the hypothesis that the reaction rate of transferable group, RT, changes depending upon the residual group, RR, in RRRTZn reagents. Copyright © 2016 John Wiley & Sons, Ltd. |
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Keywords: | acylation of diorganozincs kinetics of diorganozincs mixed diorganozincs phosphine catalyst |
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