Addition of alkali before extraction

[Taryn]

This is just a general question that I hope someone can answer.
Why do we add alkali before extraction rather than afterwards?
This is in the experiment I recently did, which was the preparation of p-Toluidine?
This was my main thought... that it helps to saturate the solution so that when ether is added the two layers form?

Any help on this question would be really helpful, just having a little bit of trouble finding something on the net.

 

[chemisttree]

I assume that the pH of the crude material was acidic? Toluidine is an aromatic base. What will happen at acidic pH to this? In this form (acidic solution) do you think that it would be soluble in ether or hexane?

 

[ravenprp]

Adding alkali before extraction is a common practice in organic chemistry. This is because alkali, such as sodium hydroxide or potassium hydroxide, helps to increase the pH of the solution. This change in pH can have several benefits for the extraction process.

Firstly, the increase in pH can help to deprotonate acidic functional groups present in the solution. This makes them more soluble in the aqueous phase, making it easier to separate them from the organic phase during extraction.

Secondly, the addition of alkali can also help to form salts with acidic compounds. These salts are more polar and water-soluble, making them easier to extract into the aqueous phase.

In the specific case of preparing p-Toluidine, adding alkali before extraction can help to convert the amine functional group into its conjugate base form. This form is more polar and can be easily extracted into the aqueous phase.

Additionally, as you mentioned, adding alkali can also help to saturate the solution and create a clear separation between the organic and aqueous layers. This is important for a successful extraction.

Overall, adding alkali before extraction can improve the efficiency and effectiveness of the extraction process, making it a common practice in organic chemistry experiments.