| Overview |
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| Operating scheme |
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; Side reactions |
Nitration of toluene to 4-nitrotoluene, 2-nitrotoluene and 2,4-dinitrotoluene |
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Synthesis instructions as PDF file for printing |
ReactionPreparation of the nitrating acid: 61.0 mL (1.11 mol) concentrated H2SO4 are slowly added under constant shaking and ice cooling to 53.0 mL (0.766 mol) ice cold concentrated HNO3, which was placed in a 250 mL wide-necked Erlenmeyer flask. Using an ice-salt cooling bath, cool the nitrating acid subsequently to -5 °C. The reaction apparatus consists of a 500 mL three-neck flask with magnetic stirring bar, an internal thermometer and a dropping funnel with pressure balance. Connect the remaining opening of the flask to a rubber tube as outlet for possibly formed nitrous gases using an adapter with ground-glass joint. The rubber tubing connects to a safety wash bottle, which is connected to another wash bottle, which contains 500 mL of aqueous 2 N NaOH solution. Charge the reaction flask with 46.1g (53.0 mL, 500 mmol) Toluene, which was freshly distilled from sodium. Cool the toluene in the reaction flask to -10 °C with an ice-salt cooling mixture. The cooled nitrating acid is placed in small portions (to avoid its warming up) into the dropping funnel of the reaction set up and is added dropwise under cooling to keep the internal temperature of the reaction mixture below 5 °C. It takes approx. 2 hours to add the entire nitrating acid. After complete addition the reaction mixture, still placed in an ice water cooling bath, is allowed to slowly warm up to room temperature. Warming up must be so slow to avoid the formation of nitrous gases. After reaching room temperature, stir the reaction mixture for additional 2 hours.Work upPour the reaction mixture into a 600 mL beaker containing 250 g of ice. Then place the mixture into a separating funnel, and extract it once with 170 mL, and twice with 40 mL of cyclohexane .
The combined organic phases are washed subsequently with 50 mL
water, 40 mL saturated aqueous
NaHCO3 solution
and again with 40 mL water. The organic phase is dried over
Na2SO4, the
drying agent is removed by filtration. The residue in the filter
is rinsed with additional 30 mL of
cyclohexane
and the solvent is removed using the
rotary evaporater. The crude product remains as an oily residue.
Crude product yield: 62.5 g; Purify the crude product by distillation at 20 hPa. The receiving flasks must be cooled. The desired product distills over in a boiling temperature range of 100-130 °C (20 hPa) yielding yellow product as a liquid and a solid distillation residue. The liquid product of the distillation crystallizes at -20 °C. Isolate the crystalline material by filtration over a cooled Buechner funnel and recrystallize it from methanol. Repeat the recrystallization step, if necessary. 4-Nitrotoluene: Yield: 3.20 g; melting point 49 °C;
Recrystallize the solid residue of the distillation from
ethanol.
Collect the crystalline product by filtation with a Buechner funnel and dry it
in an evacuated desiccator over silica gel.
2,4-Dinitrotoluene: Yield: 2.60 g; melting point 69 °C; Duration of the experiment1 day, without recrystallization.Where can I stop the experiment?Before distillationRecyclingThe evaporated cyclohexane of the reaction mixture is collected and redistilled. |
Suggestions for waste disposal |
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