| Overview |
| Instructions |
| Operating scheme |
| Substances |
| Equipment |
| Evaluation |
| Analytics |
| + |
|
|
| + |
|
; Side reactions |
Acid catalyzed acetalisation of 3-nitrobenzaldehyde with ethanediol to the correspondent 1,3-dioxolane |
 |
Synthesis instructions as PDF file for printing |
Reaction3-Nitrobenzaldehyde (15.1 g, 100 mmol), ethanediole (6.83 g, 6.20 mL, 110 mmol) and 4-toluenesulfonic acid monohydrate (1.00 g, 5.30 mmol)
are dissolved in
cyclohexane (200 mL)
in a dry 500 mL round bottom flask equipped with magnetic stirring bar, Dean
Stark trap and reflux condenser. The reaction mixture is refluxed until no
more water
is collected in the Dean-Stark trap (approx. 2-3 h
).
Work upThe hot reaction mixture is poured into another 500 mL round bottom flask to separate it from an oily sediment (800 mg) which has formed at the bottom of the reaction vessel. The sediment consists predominantly of product, starting material and 4-toluenesulfonic acid (1H-NMR spectrum). The solvent of the decanted solution is directly removed with a rotary evaporator. A yellow crystalline solid remains as
crude product.
Crude product yield: 19.7 g; melting point 50-52 °C; Purity according to GC: 95% acetale + 4% aldehyde In order to remove unreacted aldehyde as hydrogensulfite adduct, the crude product is dissolved in 200 mL tert-butyl methyl ether and extracted once with 20 mL saturated aqueous sodium hydrogen sulfite solution. The organic phase is dried over sodium sulfate, the sodium sulfate is removed by filtration and the solvent is evaporated with a rotary evaporator
to yield a nearly colorless crystalline residue.
Yield: 17.9 g; melting point 57-58 °C; Purity according to GC: more than 99%. The product is for most uses pure enough. If further purification is required, recrystallization from a solvent mixture of cyclohexane / tert-butyl methyl ether in a ratio of 1:1 (approximately 45 mL) can be carried out. The solution should be allowed to stand covered at room temperature until crystals form (if needed 1 to 2 days). If the solution is cooled quickly in an ice bath, only an oil generally forms. After cooling for a short time in an ice bath, the crystals are filtered and dried until constant mass is achieved in a desiccator at reduced pressure. Yield: 15.9 g; melting point 57-58 °C; colorless crystals; purity according to GC: more than 99%. The product can also be recrystallized from a small amount of hot ethanol, however with a much poorer yield. Duration of the experimentApproximately 5 hours including work up.Where can I stop the experiment?After evaporation of the cyclohexane from the reaction solution.RecyclingThe cyclohexane from the reaction mixture and the tert-butyl methylether are collected and redistilled. |
Suggestions for waste disposal |
||||||||||||
|