benzene substituent effects Flashcards
how does induction affect a benzene ring
creates dipole moments, push effects, removes electron density, decreases nucleophilicity
how does resonance affect a benzene ring
pull effects, adds electron density, increases nucleophilicity
which is stronger; resonance or induction
resonance
what happens when electron density is pushed into the ring
creates an o/p directing activator
what are strong activators
have a lone pair of electrons adjacent to the ring
what are moderate activators
have a lone pair next to the ring but these electrons are delocalize in resonance outside of the ring
what are weak activators
alkyl groups (R) including phenyl
what happens when electron density is pulled out of the ring
creates a meta directing deactivators
what are strong deactivators
withdraw electron density from the ring via resonance, or can accept electron density from the ring
what are moderate deactivators
no lone pair next to the ring
what is the exception to the resonance>induction rule
halogens
describe how halogens act
display strong inductive effects away from the ring and are o/p directing weak deactivators
how do we combat over substitution
use stoichiometric amounts
1 equiv = mono addition
describe steric affects on o/p directing
more bulky sub = more para product
what are the rules for competing subs
- o/p directors always beat m
- strong activators beat weak ones
- when there’s a tie, consider sterics
