[Aurelius8989]

I tried to convert carboxylic acid to ester. But I do not understand the following
[D14]Azelaic acid (30 g, 148 mmol), anhydrous MeOH (150 mL) and
concentrated H2SO4 (3 mL) was refluxed under N2 for 48 h. The solvent
was evaporated until a small amount of MeOH remained. This was then
poured onto a mixture of crushed ice and ammonium chloride, containing some ammonium hydroxide

Do I just mix the ice and NH4Cl or do I have to add the hydroxide too ?

how do i calculate the measurments required ?

[AWK]

Many beginner chemists do not understand the procedures for isolating synthesis products from the reaction mixture - in this case, it is the isolation of dimethyl nonanedioate. You need to read a good organic preparation manual.
In your case, you need to neutralize sulfuric acid and unreacted azelaic acid. The amount of concentrated ammonia must be calculated based on the amount of sulfuric acid and the assumed ester yield (e.g. 70%). Ammonium chloride with ice (3:10) forms a freezing mixture giving about -5C. In this way, you will get a solid ester (check its melting point). Then you can clean the ester by vacuum distillation (check the boiling point). Remember that your procedure has been checked many times and using it as accurately as possible will give you the best synthesis result.

[shivapharma]

Hydrolysis:- hydrolysis is a reaction with water. That is exactly what happens when amides are hydrolysed in the presence of dilute acids such as dilute hydrochloric acid. The acid acts as a catalyst for the reaction between the amide and water.

The alkaline hydrolysis of amides actually involves reaction with hydroxide ions, but the result is similar enough that it is still classed as hydrolysis.


Hydrolysis under acidic conditions

Taking ethanamide as a typical amide:

If ethanamide is heated with a dilute acid (such as dilute hydrochloric acid), ethanoic acid is formed together with ammonium ions. So, if you were using hydrochloric acid, the final solution would contain ammonium chloride and ethanoic acid.
Hydrolysis under alkaline conditions

Again, taking ethanamide as a typical amide:

If ethanamide is heated with sodium hydroxide solution, ammonia gas is given off and you are left with a solution containing sodium ethanoate.



Using alkaline hydrolysis to test for an amide

If you add sodium hydroxide solution to an unknown organic compound, and it gives off ammonia on heating (but not immediately in the cold), then it is an amide.

You can recognise the ammonia by smell and because it turns red litmus paper blue.

The possible confusion using this test is with ammonium salts. Ammonium salts also produce ammonia with sodium hydroxide solution, but in this case there is always enough ammonia produced in the cold for the smell to be immediately obvious.