Question

1. In oxidation of borneol to camphor why do we add Sodium bicarbonate??    what role it plays?? what do we want to get rid of??   what chemical reaction takes place??

2. In oxidation of borneol to camphor why do we add Sodium bisulfite??    what role it plays?? what do we want to get rid of??     what chemical reaction takes place??

Please answer my questions. 2 questions Thanks.

Answer 1

This experiment will illustrate the use of a "green" oxidizing agent, sodium hypochlo-rite (bleach) in acetic acid, for converting a secondary alcohol (borneol) to a ketone (camphor). This reaction will be followed by TLC to monitor the progress of the oxidation. The camphor is then reduced by sodium borohydride to give the isomeric alcohol, isoborneol. The spectra of borneol, camphor, and isoborneol will be compared to detect structural differences and to determine the extent to which the final step produces an alcohol isomeric with the starting material, borneol.

1) For the Extraction of Camphor we add we add Sodium bicarbonate.

Extraction of Camphor. When the reaction is complete, allow the mixture to cool to room temperature. Remove the water condenser and transfer the mixture to a separatory funnel using 10 mL of methylene chloride to aid the transfer by rinsing the any remaining Camphor in the round-bottom flask. Shake the separatory funnel remembering the ‘burp’ any methylene chloride vapor. Drain the lower organic layer from the funnel to a beaker. Extract the aqueous layer remaining in the separatory funnel with another 10-mL portion of methylene chloride, combine the two organic layers in the beaker and discard the aqueous layer. Return the organic layer to the separatory funnel and extract the combined methylene chloride with 6 mL of saturated sodium bicarbonate solution, being careful to vent the funnel frequently to release carbon dioxide gas formed from reaction with acetic acid. Drain the lower organic layer and discard the aqueous layer. Return the organic layer to the separatory funnel and extract it with 6 ml of 5% sodium bisulfite solution. Drain the lower organic layer and discard the aqueous layer. Return the organic layer to the separatory funnel and extract it with 6 ml of water. Drain the organic layer into a dry Erlenmeyer flask and add about 2 g of granular anhydrous sodium sulfate to dry the solution. Swirl gently until any cloudiness in the solution is removed. If all the sodium sulfate clumps together when the mixture is stirred with a spatula, add some additional drying agent. Cork the flask, and allow the solution to dry for about 5 minutes.

2) Wash the combined methylene chloride layers with 2.0 mL of saturated sodium bicarbonate solution. Stir the liquid with a stirring rod or spatula until bubbling produced by the formation of carbon dioxide ceases. Cap the tube and shake with frequent venting to release any pressure produced. Transfer the lower methylene chloride layer to another container and remove the aqueous layer.

Return the methylene chloride layer to the centrifuge tube, and wash this solution with 2.0mL of 5% sodium bisulfite. Transfer the methylene chloride layer to another container, remove the aqueous layer, and return the methylene chloride layer to the tube. Wash the methylene chloride layer with 2.0 mL of water and remove the aqueous layer, as just described. Using a dry Pasteur pipet, transfer the methylene chloride layer to a dry test tube or conical vial.