Laboratory Steps for the Synthesis of Lidocaine
Preparation of N-(2,6-dimethylphenyl)chloroacetamide:
Preparation of Lidocaine:
- Dispense 15 mL of glacial acetic acid in a 125 mL Erlenmeyer flask followed by 3 mL of 2,6-dimethylaniline
- Add 2 mL chloroacetyl chloride and 25 mL of half-saturated aqueous sodium acetate
- The amide should precipitate at this point and stir the product with 60 mL of cold distilled water
- Use vacuum filtration and collect the product and then press dry in the Buchner funnel
Preparation of Lidocaine:
- Transport the amide into a 100 m round bottom flask containing 7.5 mL diethylamine and 25 mL toluene
- Place a stir bar inside the flask and fix a condenser and reflux for 45 minutes
- Let the mixture cool to room temperature and transfer to a clean, dry funnel
- To remove diethylamine hydrochloride and excess diethylamine wash four times with 50 mL portions of water
- Remove and discard the aqueous layer and wash the organic layer with 20 mL 3M HCl
- Once again, remove the aqueous layer and save
- Wash the organic layer with 20 mL distilled water and remove the aqueous layer and mix with the earlier extract
- Transfer the combined extracts into a 150 mL beaker and in a ice bath, cool to 10° C
- Making sure the temperature stays under 20°C at all times, add 5mL portions of 3M NaOH until the solution is strongly basic