Chemistry - organic synthesis

According to the AQA a level specification
I need to know why substitution reactions occur in preference to addition reactions in aromatic compounds?
Could anyone please give an A-level chemistry response or links to any good websites which give a good explanation as to why?

Tysm

Reply 1

bl0bf1sh

Original post by Lebkuchen

If an aromatic compound were to undergo an addition reaction, it'd lose the delocalisation, lose the aromaticity, and therefore lose stability – not favourable.
For substitution reactions on an aromatic compound, the aromaticity is maintained :smile:

Chemguide usually explains things pretty well: https://www.chemguide.co.uk/organicprops/arenesmenu.html

Reply 2

Scanjo63

As above addition will destroy delocalisation of the pi electrons which is an endothermic process requiring an input of energy, might be an idea to review the structure of benzene and a little about its history then you might see why this idea of delocalisation is important.
https://www.science-revision.co.uk/A2_benzene_structure.html