A Kinetic Study on the Nucleophilic Substitution Reactions of Dinitrodiphenyl Ethers or Bromonitrobenzenes with Sodium Nitrophenoxides

Abstract

Rates of reactions of an excess amount of sodium nitrophenox Ides with several dinitrodiphenyl ethers or bromonitrobenzenes in 1, 3-dimethy1-2-imidazolidinone (dipolar aprotic solvent) have been measured. Rate parameters and activation parameters calculated from the Arrhenius standard expressions were summarized in Table 1 and Table 2. It was found from the rate parameters that the ratio of 2, 2'-, 2, 4'- and 4, 4'-isomer of dinitrodiphenyl ether was 3.8 : 34.9 : 61.3 respectively under the conditions of the equilibrium state at 120°C with an equally excess amount of sodium o- and p-nitrophenoxides. The correlation between entropies of activation at 120°C, ΔS^≠, and enthalpies of activation, 41--P, was shown in Fig.1. These plots could be classified into four groups an d each of them showed a good linear free energy relationhip. Group 1, 2 and 3 in Fig.1 had a sam e isokinetic temperature of 71°C and the rate of reaction at this temperature was 3.9 x 10^-5, 8.9 x 10^-8 and 3.6 x 10^-8s^-1respectively, so the rate ratio of nucleophilic activity of m-, p- and o-nitrophenoxide ion could be determined as 440 : 1: 0.4 respectively. Group 4 in F ig.1 had an isokinetic temperature of 216°C and the rate of reaction at this temperature was 2.0 x 10^-3 s^-1. The activation parameters for reaction 5 which rate was too slow to measure could be calculated as ΔH^≠ =10.6 kcal/mol, ΔS^≠ at 120°C= 62.1 cal/mol, that was well located on the line of group 3.