Question

How are the following preparation carried out .
Benzaldehyde from Toluene.

Answer 1

Benzaldehyde is a colourless liquid with a smell of almond oil. The melting point for benzaldehyde is $- {26^o}C$ and a boiling point is ${179^o}C$. It is only slightly soluble in water but it is completely soluble in ethanol and diethyl ether. It is strongly refractive in nature. It is denser than water.

Complete step by step answer:
Benzaldehyde is an organic compound which is an aldehyde with a chemical formula of ${C_6}{H_5}CHO$. Toluene is also an organic compound with the chemical formula of ${C_6}{H_5}C{H_3}$. In toluene a methyl group is attached to benzene ring, while in benzaldehyde an aldehyde group is attached to benzene ring
So to prepare benzaldehyde from toluene we can do the side chain chlorination of toluene to benzylidene chloride. Then further the process of hydrolysis takes place in which the formation of benzaldehyde and two moles of hydrochloric acid is formed as a product. The equation for toluene with chlorine is given below,
${{C}_{6}}{{H}_{5}}C{{H}_{3}}+C{{l}_{2}}\xrightarrow{heat}{{C}_{6}}{{H}_{5}}CHC{{l}_{2}}+{{H}_{2}}$ ${{C}_{6}}{{H}_{5}}CHC{{l}_{2}}\xrightarrow[heat]{hydrolysis}{{C}_{6}}{{H}_{5}}CHO+2HCl$
Now the above main product called benzylidene chloride will undergo hydrolysis. The equation for this is the following,
${{C}_{6}}{{H}_{5}}CHC{{l}_{2}}\xrightarrow[heat]{hydrolysis}{{C}_{6}}{{H}_{5}}CHO+2HCl$
So at the end the product formed are benzaldehyde and hydrochloric acid.

Note: Toluene is a colourless liquid with an aromatic odour. It is used as a solvent in making paint, paint thinners, nailpolish, adhesives, rubber, lacquer. It is also used in the leather tanning process. It is not acidic. It is generally found in crude oils. It is a respiratory irritant and affects the central nervous system. it causes nausea, dizziness, and headache.