video tutorial o-Nitrotoluene using nitric acid in DCM

Summary: Ortho-nitrotoluene synthesis via in-situ HNO3 in DCM

• Goal: nitrate toluene selectively at the ortho position using nitric acid dissolved in dichloromethane (DCM).
• In-situ generation of HNO3 in DCM:
  • 25 mL concentrated sulfuric acid was cooled.
  • 40 g potassium nitrate ground to a fine powder was added, forming a thick gel with nitric acid fumes.
  • Dry nitrate dissolved in approx. 90 mL DCM to form the nitrating solution (pale yellow, gelatinous solid upon stirring).
• Reactivity tests in the DCM/HNO3 solution showed no reaction with aluminum foil, sugar, or heated foil, suggesting lack of water.
• Nitration of toluene:
  • 25 mL toluene used; assumed ~60% of nitrate transferred to DCM.
  • Reaction performed in an ice bath, starting near 6 °C; minor exotherm to ~11–18 °C; maximum ~18 °C.
  • After ~1 hour, warmed to room temperature and stirred for another hour; color evolved from orange to golden yellow, then red/orange, and back toward yellow with temperature changes.
• Workup and isolation:
  • Quenched with water, separated organic phase, and washed the organic layer with saturated sodium bicarbonate solution (then with water).
  • Removed solvents by distillation; collected 9.5 g of yellow liquid (nitro-toluene; strong almond/aroma) from the organic layer.
  • Purified by freezing; yield ~29% based on toluene used; product resembled the ortho isomer from previous mixed-acid nitration runs.
• Isomer check:
  • Cooling to −12 °C did not produce crystallization or turbidity, inconclusive for pure ortho-nitrotoluene but encouraging.
  • Papers claim near-pure ortho isomer; further testing required for confirmation.
• Outlook:
  • Recommend extending reaction/workup to ~12 hours at the reaction temperature to potentially improve yield of the ortho isomer.