What is electrophilic aromatic substitution?
A reaction where an electrophile replaces a hydrogen on an aromatic ring
Why does benzene undergo substitution instead of addition?
To preserve aromaticity
What forms when the electrophile first attacks benzene?
An arenium ion (sigma complex)
What is the rate-determining step in EAS?
Formation of the sigma complex
What does the energy diagram of EAS contain?
Two transition states and one high-energy intermediate
What is the electrophile in Friedel-Crafts alkylation?
A carbocation
What catalyst is commonly used in Friedel-Crafts reactions?
AlCl3
What is the electrophile in Friedel-Crafts acylation?
An acylium ion
What is a limitation of Friedel-Crafts alkylation?
Carbocation rearrangement
What substituent effect donates electrons via sigma bonds?
The inductive effect
What substituent effect donates electrons through pi overlap?
The resonance (mesomeric) effect
What is an ortho-para directing group?
An electron-donating group
What is a meta-directing group?
An electron-withdrawing group
How do halogens direct electrophilic substitution?
Ortho-para directing but ring-deactivating
Why do electron-donating groups activate the ring?
They increase electron density
Why do electron-withdrawing groups deactivate the ring?
They reduce electron density on the ring
What positions are available on a substituted benzene ring?
Ortho, meta, para
What effect does a nitro group have on the ring?
Strongly deactivating and meta-directing
What type of mechanism explains directing effects?
Resonance of sigma complex intermediates
What is a mesomeric effect?
Electron donation or withdrawal through a pi system
