No abstract

Substituted nitrobenzenes were among the first organic compounds to be investigated using the polarographic technique. The early work was performed by the Japanese, Shikata and his co-workers, and from this work Shikata and Tachi3 formulated the "electronegativity rule of reduction potentials," i. e., that organic compounds are more easily reduced as more electronegative groups are substituted in the same molecule.These investigators measured the reduction potentials by the tangent method us. the normal calomel electrode. This method of measurement deviates from present practice. I t was felt desirable to extend their investigations of substituted nitrobenzenes and to determine the relative effect of the position of the substituent upon the reduction process.The ortho-, meta-and para-isomers of nitrobenzoic acid, dinitrobenzene, nitrochlorobenzene, and nitrotoluene were selected for study. The reduction of these compounds a t the dropping mercury cathode from carefully buffered solutions over the PH range 2 to 14 was investigated to determine the nature of the reduction process and the effect of the position of the substituent groups upon the half-wave reduction potential. ExperimentalAll of the compounds investigated were obtained from Eastman Kodak Company and were further purified before use. Water solutions of 0.002 M concentration of oand m-nitrobenzoic acids and of 0.001 M concentration of

No abstract

exchange resins such as Amberlite IR-4B, Deacidite, L and Amberlite IRA-400 are excellent catalysts for promoting Knoevenagel condensations between aldehydes and esters, such as ethyl cyanoacetate, ethyl acetoacetate, and diethyl malonate. Condensations with diethyl malonate cannot be accomplished at room temperature but may be carried out by refluxing in

The nitroparaffins have long been recognized as pseudo acids. They dissolve in alkaline solution through the formation of salts according to the equation This neutralization is a relatively slow process and the rates of neutralization by different bases have been investigated by Maron and La Mer3 and more recently by P e a r~o n .~ In both investigations the reaction rate was followed conductometrically.De Vries and Ivett5 reported that the wave heights for the reduction of nitroparaffins were proportional to the concentration of the nitroparaffin when 0.05 mo1a.r sulfuric acid was used as the supporting electrol.yte but that this relationship was not linear when 0.05 molar sodium sulfate was used in place of sulfuric acid. When sodium sulfate was used as the supporting electrolyte the @H increased as the reduction progressed because hydrogen ions were used up in the reduction process. This increase in @H caused a shift in the equilibrium between the normal and aci-forms of the nitroparaffin in favor of the aci-form which was not reducible a t the dropping mercury cathode. As the concentration of the nitroparaffin was increased the pH became still greater resulting in still more of the aci-nitroparaffin being formed and consequently the wave height was not proportional to concentration. The nitroparaffins could not be reduced in 0.1 N sodium hydroxide or 0.1 N tetramethylammonium hydroxide. This investiga-R-CHzNOz -t OH-+ R-CH-NO2-+ Hz0(1) Presented before the Division