Chp 18: Aromatic Rxns

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Side Chain: Halogenation

Reagents: Br₂, Cl₂, NBS, hv → attacks more sub. radical C

Side Chain: Oxidation

Reagents:
1. KMnO₄, H₂O, heat

2. H₃O⁺

OR
Na₂Cr₂O₇, H₂SO₄

cannot oxidize quaternary C’s

Side Chain: Reduction

Metal catalyst: H₂ , Pt/Ni (complete)

Clemmensen (carbonyls): Zn(Hg), HCL, heat

Wolff-Kishner (carbonyls): H₂N-NH₂, KOH, heat

Reducing Nitrate → Amine

Option 1: H₂, Pd/C

Option 2:

1. Zn/Fe, HCl

2. NaOH

Side Chain: Substitution (SN) Rxns

SN2: strong nuc (e.g., NaOH), 1° or 2° preferred

SN1: weak nuc (e.g., H₂O, EtOH), 3° preferred (C+)

no heat

Side Chain: Elimination Rxns

E2: strong base (tBuOK, NaOEt)

E1: weak base OK (EtOH…)

both favor tertiary C+ and heat

if OH is LG: H₂SO₄, conc, heat

Full Reduction of Benzenes

Reagents: H₂, Pt/Pd/Ni (inert metal)

Birch Reduction

Reagents: Na, CH₃OH, NH₃

reduces 1 pi bond, if EDG on it: not reduced, if EWG on it: reduced

EAS: Halogenation

Reagents: Br₂, FeBr₃

Cl₂, AlCl₃

I₂, HNO₃
Electrophile: halide cation (I+, Br+, Cl+)

EAS: Sulfonation

Reagents: fuming, conc. H₂SO₄

Electrophile: -SO₃ (SO₃H group added to ring, H is added at the end)
REVERSIBLE: dil. H₂SO₄ → useful as a BLOCKING GROUP

EAS: Nitration

Reagents: HNO₃, H₂SO₄

Electrophile: NO₂

EAS; FC Alkylation

Reagents: R-Cl, AlCl₃

Cons: C+ rearrangement, polyalkylation, can’t rxt w/ strong EWGs on ring (NO₂)

Electrophile: carbocation

EAS: FC Acylation

Reagents: R-C=O-Cl, AlCl₃

Only adds 1 group, no rearrangement, can’t rxt w/ EWGs

Electrophile: acylium cation

EAS: Gatterman-Koch

Reagents: CO, HCl, AlCl₃/CuCl

Adds aldehyde group

NAS: S_NAR (Addn-Elimination)

Reagents: strong nuc (NaOEt, NaOH) (benzene is electrophile)

Requirements: strong EWG (e.g., NO₂) ortho or para to LG (halide)

NAS: Benzyne Mech.

Reagents: 1. NaNH₂, NH₃, 2. H₃O⁺

OR: 1. NaOH, hot, 2. H₃O⁺

No strong EWG needed

If a sub is para to LG, then addn. is para or meta to the sub (racemic)

Protecting Rxns

For NH₂ → NH-COCH₃: CH₃COCl, py

NH₂ (EDG) directly rxting w/ HNO₃ results in NH₃⁺ → strong EWG, deactivates ring

deprotect: 1. 2. H₃O⁺, 2. OH^-