Question

The following reaction:
\[{{C}_{6}}{{H}_{5}}N{{H}_{2}}\xrightarrow[{{0}^{o}}]{NaN{{O}_{2}}/HCl}X\xrightarrow{CuCN}Y\xrightarrow{{{H}_{2}}O/{{H}^{+}}}Z\], Z is defined as :
A) \[{{C}_{6}}{{H}_{5}}-NH-C{{H}_{3}}\]
B) \[{{C}_{6}}{{H}_{5}}-C{{H}_{2}}-N{{H}_{2}}\]
C) \[{{C}_{6}}{{H}_{5}}-C{{H}_{2}}-COOH\]
D) \[{{C}_{6}}{{H}_{5}}-COOH\]

Answer 1

Hint:On seeing the reaction we can identify that a diazonium salt will be formed. Diazonium is ionic in nature. They are water soluble and the aryl diazonium are colourless crystallized solids. This process of converting primary aromatic amine to diazonium salts is known as dissociation or diazotization.


Complete solution:
When \[{{C}_{6}}{{H}_{5}}-N{{H}_{2}}\]is reacted with hydrochloric acid and \[NaN{{O}_{2}}\]a diazonium salt is formed which is known as benzene diazonium chloride and the chemical formula of the compound is \[{{C}_{6}}{{H}_{5}}-{{N}_{2}}^{+}C{{l}^{-}}\]. When the benzene diazonium chloride is further reacted with CuCN an aryl nitrile or benzene nitrile is formed. The formula for benzene nitrile is \[{{C}_{6}}{{H}_{5}}CN\]. On further reaction of aryl nitrile with water and hydrogen ion an acid is formed. That acid is known as benzoic acid and the chemical formula of that is \[{{C}_{6}}{{H}_{5}}-COOH\].
So the compound X is \[{{C}_{6}}{{H}_{5}}-{{N}_{2}}^{+}C{{l}^{-}}\]benzene diazonium chloride
The compound Y is \[{{C}_{6}}{{H}_{5}}CN\]benzene nitrile
The compound Z is \[{{C}_{6}}{{H}_{5}}-COOH\]benzoic acid.
Benzoic acid is a colourless solid with a monoclinic structure. Due to the presence of aromatic rings around the compound it has a faintly pleasant odour. It is soluble in acetone and alcohol. The acid dissociation constant of benzoic acid is 4.2.

Hence, the correct option is (D).


Note: Diazonium salts are highly unstable under normal conditions. The benzene diazonium chloride only reacts when it is warmed. They are not soluble in water. They are used in dye and pigment industries. They are used in document reproduction. They are used in preparation or formation of many organic compounds.