Multivariate analysis in selective reduction of m-iodonitrobenzene by aqueous ammonium sulfide under liquid-liquid phase transfer catalysis

Reduction of m-iodonitrobenzene (m-INB) was conducted under a liquid-liquid phase transfer catalysis system using aqueous ammonium sulfide. This process yielded m-iodoaniline (m-IA) as the sole product. An experimental design based on response surface methodology was utilized to optimize the conversion of m-INB. Box-Behnken design was employed to assess both individual and interactive effects of experimental variables (temperature, catalyst concentration, m-INB concentration, and NH₃/sulfide mole ratio) on the reduction of m-INB. A reliable quadratic regression model was developed, demonstrating strong predictive capability using the experimental design data. Optimization via a desirability function predicted a maximum m-INB conversion of 100 % under the following operating conditions: temperature 321.5 K, catalyst concentration 0.074 kmol/m³ , m-INB/sulfide ratio 0.233, and NH₃/sulfide mole ratio 3.78. The analysis of variance, which yielded an R² value of 99.4 % for m-INB conversion, confirmed strong agreement between experimental outcomes and predicted values obtained from the fitted model. Thus, this study effectively demonstrates the advantages of experimental design to model reaction parameters for m-IA production.