Question

a separation and purification scame conclustion

the benzoic acid melting point 122

and dibromobenzene 82

Answer 1

Here, we have three components system, where the components are:

1. Benzoic Acid
2. Benzoin
3. 1,4-Dibromobenzene

So initially all the three compounds are dissolved in Diethylether (DEE).

Reason: Since Ether is neutral and non reactive towards all the compounds present over here and towards wide range of organic compounds, hence, we can use it as solvent.

After dissolving all the compounds and analysing their properties, we know one is acidic, one is basic and one is Neutral. Hence, we add weak base NaHCO_​​3​ and precipitate our Benzoic acid and separate it from mixture.

We recover it by neutralizing NaHCO_​​3 with a strong acid (HCl) over here.

Then we use solvent extraction method, for separation of benzoin and 1,4-Dibromobenzene. In this method, DCM forms an immiscible layer with DEE and since DCM is more polar it interacts with benzoin and extracts it from solvent i.e DEE.

Finally we can obtain benzoin by recrystallizing it by reaction with hot Methanol and 1,4-Dibromobenzene can be recrystallized by reaction with toluene.