Question

Question: How would you synthesize the following compounds from benzene? Assume that ortho and para isomers can be separated.

a)

b)

Short answer

a)

b)

Step-by-step solution

Synthesis of Compound A from benzene

For the formation of ortho bromo para nitro toluene from benzene firstly make aren’t benzene that is toluene by reacting the benzene with methyl chloride in presence of aluminium chloride now nitro is at para nitration is done in the presence of nitrous acid and followed by bromination in presence of ferrous bromide to add bromide at the ortho bromination because para is already filled.

Nitration is done before bromination because if bromination done first then para position is occupied by the Br ion but as per product formation nitro is present at para.

Mechanism for compound A formation

The steps followed as:

1. Parent benzene is formed that is toluene
2. Nitration occurs so nitro present at para
3. Bromination so Br occupy ortho position
4. o-bromo p- nitro toluene formed

Synthesis of Compound B from benzene

As per the formation of the compound the benzene first do acylation with the acyl chloride then followed by chlorination at the meta position in presence of ferrous chloride and then the removal of carbonyl is occur which is done by the Lindlar’s catalyst then sulphonation occur at the ortho position.

Mechanism for compound B formation

The steps followed as:

1. Acylation of benzene occurs on reacting with ${\left({\mathrm{CH}}_3\right)}_2\mathrm{CHCOCI}$
2. Chlorination in the presence of ${\mathrm{CI}}_2,{\mathrm{FeCI}}_3$
3. Reduction of the carbonyl in the presence of ${\mathrm{H}}_2/\mathrm{Pd},\mathrm{C}$
4. Sulphonation in the presence of${\mathrm{SO}}_3,{\mathrm{H}}_2{\mathrm{SO}}_4$