Chapter 16: Electrophilic Aromatic Substitution

Friedel-Crafts Alkylation

adds C-C through R-Cl and AlCl3

R must be alkyl (RX)

FC alkylation, 3 prime, C=C, on end

aryl + vinyl halides don’t react

no reaction occurs if the aromatic ring contains a strongly EWG or amine

both!!

EWG reduce nucleoephility of aromatic ring

reaction is difficult to stop at mono alkylation stage

FC alkylation

product is more reactive than starting material

skeletal rearrangement of alkyl substituting can occur

FC alkylation

1 alkyl halides = bad! (hydride or alkyl shift)

friedel-crafts acylation

addition of acyl group (O=R)

reaction stops at mono____ stage

FC acylation

no carbocation rearrangements

FC acylation

electron-donating groups

activating groups b/c increase energy of pi electrons = speed up reaction

electron-withdrawing groups

deactivating groups b/c decrease energy of nucleophile

-OH

EDG, ortho/para

-NH-C=O-CH3

EDG, ortho/para

-CH3

EDG, ortho/para

-C(CH3)3

EDG, ortho/para

-CH2Cl

weak EWG, ortho/para

-F

weak EWG, ortho/para

-Cl

weak EWG, ortho/para

-Br

weak EWG, ortho/para

-I

weak EWG, ortho/para

everything else

weak EWG, meta directing

inductive effect

the withdrawal or donation of electrons through a σ bond due to electronegativity

• decreased electron density = deactivating

resonance effect

the withdrawal or donation of electrons through a pi bond due to overlap of p orbital on substituent w/p-orbital on aromatic ring