[Siddy]

Hi,
Ive got a question from uni that asked for a practice way of converting Toluene to Bromobenzene. I think it has to be a few steps.
Any ideas?

[Custos]

It will be at least two steps. Bromination of the benzene ring is relatively straight forward but then you have to get rid of the methyl group. One way is oxidation to a benzoic acid and decarboxylation. However if you are going to oxidize toluene to benzoic acid anyway (using KMnO₄ for example) you could get directly to bromobenzene conveniently through the silver salt (look up the Hunsdiecker reaction). Hope that helps.

[Siddy]

Thanks!
Im on the right track now

[Siddy]

ok, i miss read the question.

Its supposed to be, toluene > benzene.

I think bromobenzene was a hint?

Anyone know how to turn halobenzene back to benzene, H2 and catalyst?

[russellm72]

Use the same approach.

Oxidise up to benzoic acid make the silver salt and do a Hunsdiecker affording the halo benzene. This can be dehalogenated by a variety of ways e.g. SmI2, hydrogenation,diazotisation followed by phosphorous acid, metal insertion followed by acid workup....

Any other ideas in less steps?

R.

[Custos]

Direct decrboxylation of the benxoic acid to benzene is possible. Sodium hydroxide and heat should do it. One less step.

[Siddy]

Thats an interesting one, looking into it now.
might do a bit of a write up.

[Siddy]

According to my research, Benzoic Acid + NaOH solution > Sodium Benzoate

Is Benzene formed from that product?
All i can find is un-scientific reports of a reaction with "vitamin-c", is there a for scientific way of producing benzene in high yields?

Ive also found, Toluene + H2 > benzene + CH3
with a silicon dioxide and aluminium oxide catalyst
any one have experience?

[Borek]

According to my research, Benzoic Acid + NaOH solution > Sodium Benzoate

Is Benzene formed from that product?

Depends on conditions. In 'normal' conditions you will get just a sodium benzoate, in high NaOH concentrations and high temperatures you may see benzene and CO₂ between products.