Question

After the extractive work-up, if litmus paper turned red when dabbing the paper with a glass rod which touched the aqueous solution of your extractive work-up then what would you do?

a. Before proceeding to performing a final drying of the organic solvent containing the target compound (methyl salicylate) using drying salts followed by vacuum filtration and concentration of the organic solvent....one should repeat the extraction (or sometimes called wash) of the organic layer with a fresh aqueous solution of NaHCO3 and then retest the aqueous layer to ensure that it turns blue. This is to make sure all trace acids have been neutralized properly.

b. Before proceeding to performing a final drying of the organic solvent containing the target compound (methyl salicylate) using drying salts followed by vacuum filtration and concentration of the organic solvent....one should repeat the extraction (or sometimes called wash) of the organic layer with a the same aqueous solution of NaHCO3 that was used prior, and then retest the aqueous layer to ensure that it turns blue. This is to make sure all trace acids have been neutralized properly.

c. Before proceeding to performing a final drying of the organic solvent containing the target compound (methyl salicylate) using drying salts followed by vacuum filtration and concentration of the organic solvent....one should repeat the extraction (or sometimes called wash) of the organic layer with the same aqueous solution of NaHCO3 that was used prior, and then retest the aqueous layer to ensure that it turns a more distinct red. This is to make sure all trace acids have been neutralized properly.

d. Nothing. Just proceed to performing a final drying of the organic solvent containing the target compound (methyl salicylate) using drying salts followed by vacuum filtration and concentration of the organic solvent.

Answer 1

option a is correct that is Before proceeding to performing a final drying of the organic solvent containing the target compound (methyl salicylate) using drying salts followed by vacuum filtration and concentration of the organic solvent....one should repeat the extraction (or sometimes called wash) of the organic layer with a fresh aqueous solution of NaHCO3 and then retest the aqueous layer to ensure that it turns blue. This is to make sure all trace acids have been neutralized properly.

This is because NaHCO3 reacts with unreacted salicylic acid to form sodium salicylate, water and CO2 as a by product and hence thorough washing is must