Unit 7 Nomenclature + aromaticity + activation/deactivation identification

toluene structure

phenol

anisole

aniline

benzaldehyde

benzoic acid

if using common name of substituted benzene with multiple functional groups, which one gets #1 when numbering the chain?

the group that is part of the common name of the benzene

propane = ___ # of carbons in chain

3 carbons

pentane = ___ # of carbons in chain

5 carbons

ethane = ___ # of carbons in chain

2 carbons

butane = ___ # of carbons in chain

4 carbons

heptane = ___ # of carbons in chain

7 carbons

ortho =

next to main functional group

meta =

2 away from main functional group

para =

3 away from main functional group

first rule for aromaticity

must be ring comprised of continuously overlapping p orbitals (all carbons are sp2)

second criteria for aromaticity

ring must contain an odd number of pairs of pi electrons (do not count cations) DO count lone pairs participating in pi system

antiaromatic if…

meets first criteria (continuous pi system), but fails second (odd number of pairs of pi electrons)

nonaromatic if…

fails first criteria (continuous pi system/all sp2 C)

a lone pair on sp2 element exists in p orbital IF

the lone pair can participate in a pi system and can be delocalized

CANNOT perform friedel-crafts on _____ or ______ ______ ring / CAN on weakly _______ or activated ring

CANT on: moderately or strongly deactivated

CAN on: weakly deactivated

if halogen on benzene…

weak deactivator BUT ortho, para director

moderate deactivator

groups that withdraw electron density from the ring via resonance (usually if there is a pi bond/triple bond to a electronegative element)

strong deactivator

very powerfully electron withdrawing

• such as multiple halogens as this creates only inductive effect without resonance → Cl3

• NO2

• NR3 (puts positive charge on nitrogen creating strong inductive effect as nitrogen is highly electron poor)

strong activator

lone pair next to the ring that can easily donate electron density

moderate activator

lone pair next to ring but it is tied up in resonance outside of the ring as well so it is less participatory in the pi system

weak activator

alkyl groups (side chains)

• CH3

• Tert-butyl

• ethane

activators direct to …

ortho and para (para is usually major product though due to sterics)

deactivators direct to …

meta position EXCEPT for halogen deactivators

ortho para directors always beat …

meta directors (deactivators)

strong activators always beat …

weak activators