88785-76-6Relevant articles and documents
Metal ion promoted hydroxide ion and water catalyzed hydrolysis of amides. Effects of the acyl group and the leaving group
Fife, Thomas H.,Bembi, Ramesh
, p. 11358 - 11363 (2007/10/02)
The hydrolysis of anilide derivatives of N-methyl-4-nitroaniline in H2O is hydroxide ion catalyzed; plots of log kobsd vs pH are linear with slopes of 1.0 at pH > 8. When there is a chelating functional group in the acyl portion of the molecule (1,10-phenanthrolinyl or 6-carboxypicolinoyl) and in the presence of saturating concentrations of Cu2+, Co2+, or Zn2+, hydroxide ion catalyzed reactions are observed at pH > 4 (rate enhancements range from 104- to 105-fold), and pH-independent reactions occur from pH 1 to 4. Rate constants are very nearly the same in the metal ion promoted hydrolysis reactions for the anilides with these acyl groups. Thus, the negatively charged carboxylate ligand of N-(6-carboxypicolinoyl)-N-methyl-4-nitroaniline is equally good in facilitating the metal ion promoted hydrolysis reactions as the neutral ligands of the 1,10-phenanthroline derivative. A trifluoroacetyl acyl group produces the same general effect as a chelated metal ion, i.e., a facile OH--catalyzed reaction and a pH-independent reaction at pH 6 is favorable (kOH' = 1.0 × 104 M-1 s-1 at 50 °C), even though the pKa of the anilide N-H function is 5.5 and the second-order rate constant (kOH') is tnat for attack of OH- on the ionized species. Amide deprotonation does not have a large effect on the rate of hydrolysis; ionization of the amide N-H function of N-(trifluoroacetyl)-2-carboxy-4-nitroaniline produces only a 7-fold decrease in kOH. An N-methyl group accelerates the rate of hydrolysis of the (trifluoroacetyl)-2,4-dinitroanilide. N-(Trifluoroacetyl)-N-methyl-2,4-dinitroaniline hydrolyzes very rapidly at 50 °C, kOH = 5 × 106 M-1 s-1 and k0 = 10-2 s-1. The pH-independent reaction governed by k0 proceeds 2.1-fold more slowly in D2O than in H2O. General base catalysis occurs, and the Bronsted coefficient β is 0.3.
