Phenyl acetate Bronsted plot

Fig. 18. Bronsted plot for the reactions of nucleophiles with phenyl acetate (PA,D)p-nitrophenyl acetate (PNPA, A) and 2,4-dinitrophenylacetate (DNPA,0) at 25°C. The open symbols (and full lines) represent data for the total reaction, which is in most cases nucleophilic catalysis. The closed symbols (and broken lines) represent general base catalysis of hydrolysis.

Data for the reactions of several cyclic tertiary amines with phenyl, 4-nitro-phenyl and 2,4-dinitrophenyl acetates, at 25°C and ionic strength 1.0, appear in Table 40, and as a Bronsted plot in Fig. 20. The usual irregularities of such plots for nucleophilic attack are evident. Linear relationships between log k and pKa are generally found for groups of compounds of closely similar structure, as for the substituted pyridines in Fig. 20. The data for the two tricyclic amines fall on separate curves, and the points for imidazole clearly fall on neither of the first two sets of lines. The separate lines for the reactions of particular classes of nucleophile are approximately parallel, as is usually found. 

Fig. 20. Bronsted plot of the rate coefficients for the tertiary amine-catalyzed hydrolysis of phenyl (0),p-nitrophenyl (A) and 2,4-din itrophenyl ( ) acetates at 25°C. (Data from ref. 283).

Fox, J.P., Jencks, W.P. General acid and general base catalysis of the methoxyami-nolysis of 1-acetyl-l,2,4-triazole. J. Am. Chem. Soc. 1974, 96(5), 1436-1449. Bruice, T.C., Donzel, A., Huffman, R.W., Butler, A.R. Aminolysis of phenyl acetates in aqueous solutions. VII. Observations on the influence of salts, amine structure, and base strength. J. Am. Chem. Soc. 1967, 89(9), 2106-2121. Williams, A., Jencks, W.P. Acid and base catalysis of urea synthesis nonlinear Bronsted plots consistent with a diffusion-controlled proton-transfer mechanism and the reactions of imidazole and N-methylimidazole with cyanic acid. J. Chem. Soc. Perkin Trans. 2. 1974, 1760-1768. 

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