Question

Accomplish the following conversions:
Aniline to benzyl alcohol

Answer 1

To answer this question, you must recall the various reactions and reagents in organic chemistry. An Aniline group can be substituted easily to prepare a large variety of compounds by preparing its diazonium salt.

Complete step by step solution:
Diazonium salts are a group of organic compounds that contain the functional group . The nitrogen group is covalently bonded to an organic compound, may be either an alkyl or aryl group and the X denotes an organic or inorganic anion, commonly halide ions are used. It is not a very stable group and thus is very reactive. It can be easily substituted by a number of nucleophiles producing nitrogen gas as a side- product.
Here, we convert aniline to benzene diazonium chloride. It is a salt of the diazonium cation and chloride anion. It is formed from aniline by treating it with sodium nitrite and hydrochloric acid at low temperatures of around 273- 278 Kelvin. The attacking species is ${\text{HN}}{{\text{O}}_{\text{2}}}$ and it is formed in- situ due to its high reactivity.
After the benzene diazonium chloride is formed, we substitute the diazo group with a cyanide group in order to increase the number of carbon atoms. For this we use the Sandmeyer reaction treating the diazonium salt with potassium chloride in presence of copper cyanide. We obtain benzonitrile.
Now we have to remove the nitrogen atom and for that we hydrolyze benzonitrile to produce benzoic acid. Benzoic acid can then be reduced easily to obtain benzyl alcohol.

Note:
It should be noted that the reactions involving diazonium salt must be carried out at a temperature less than $278{\text{ K}}$ above which it becomes unstable and dissociates.