video tutorial p-Nitrobenzoic acid from p-nitrotoluene using dichromate (narrated by James Earl Jones)
Objective: oxidize 8.5 g pyrro nitro toluene to pyronitrile benzoic acid (85% yield).
Reagents/conditions: potassium dichromate (28 g, ~1.5 equivalents) in water (45 mL) with concentrated sulfuric acid added slowly via a pressure-equalized addition funnel; stirring and controlled acid addition; reflux and heating; milky distillate from unreacted nitrotoluene; color changes to green indicate reaction progress.
Workup: cool and precipitate product by ice; filter crude (about 12 g, green/brown); wash and dry.
Purification: dissolve crude in 100 mL water with 4.5 g NaOH to form sodium salt; chromium removed as chromium hydroxide; reacidify filtrate with 10 mL conc HCl to precipitate product again; filter and dry.
Final product: 8.8 g of pyronitrile benzoic acid; yellow color; minor chromium salts present; total yield ~85% of starting material; suitable for subsequent reactions.
Notes: reaction is exothermic and requires closed apparatus; scale-up requires caution; benzene recrystallization avoided for safety.
