CIE A Level Chemistry复习笔记3.9.3 Synthetic Routes

• Students should be able to critically analyse given synthetic routes and determine whether appropriate reagents and reaction conditions are used
• Students should also be able to predict possible by-product of a synthetic reaction

Worked Example: Two-step synthesis

Answer

The correct answer is  D

The first step involves a nucleophilic addition of CN- using NaCN as catalyst and heat to form a hydroxynitrile.

In the second step, the nitrile is refluxed with dilute aqueous sulfuric acid causing hydrolysis of the nitrile forming a carboxylic acid and ammonium salt.

Worked Example: Synthesis of hexanoic acid

Answer

The correct answer is C

Halogenoalkanes can undergo nucleophilic substitution with ethanolic KCN in which the CN- ion acts as a nucleophile and replaces the chlorine atom in 1-chloropentane to form a nitrile.

The treatment of nitriles with concentrated hydrochloric acid will produce a carboxylic acid and an ammonium salt.

In this case, hexanoic acid and ammonium chloride will be formed.