145.
Temperature dependences of the relative reactivity of potassium aryloxides XC
6H
4O
?K
+ toward 2,4‐dinitrophenyl benzoate in 50 mol% dimethylformamide (DMF)–50 mol% H
2O mixture have been studied using the competitive reactions technique. Correlation analyses of the relative rate constants
kX/
kH and differences in the activation parameters (ΔΔ
Н≠ and ΔΔ
S≠) of the competitive reactions have revealed the existence of two isokinetic series of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides with electron‐donating substituent (EDS) and electron‐withdrawing substituent (EWS), respectively. We have investigated the effect of the substituent X on the activation parameters for each isokinetic series and concluded that the mechanism of the reactions of 2,4‐dinitrophenyl benzoate with potassium aryloxides XC
6H
4O
?K
+ in 50 mol% DMF–50 mol% H
2O mixture is the same as in DMF. Analysis of the obtained data with using the method of two‐dimensional reaction coordinate diagram leads to the conclusion that the variation of the solvent from DMF to 50 mol% DMF–50 mol% H
2O mixture affects the reaction pathway. The rate constant
kX for the reaction of 3‐nitrophenyl benzoate with potassium 4‐methoxyphenoxide and the relative rate constants
kX/
kH for the reaction of 3‐nitrophenyl benzoate with potassium aryloxides XC
6H
4O
?K
+ with EDS were measured in 50 mol% DMF–50 mol% H
2O mixtures at 25°C, and it has been shown that the addition of water to DMF does not change the mechanism but slows down these reactions.
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