Ch. 18 - Reactions of Aromatics: EAS and BeyondSee all chapters
All Chapters
Ch. 1 - A Review of General Chemistry
Ch. 2 - Molecular Representations
Ch. 3 - Acids and Bases
Ch. 4 - Alkanes and Cycloalkanes
Ch. 5 - Chirality
Ch. 6 - Thermodynamics and Kinetics
Ch. 7 - Substitution Reactions
Ch. 8 - Elimination Reactions
Ch. 9 - Alkenes and Alkynes
Ch. 10 - Addition Reactions
Ch. 11 - Radical Reactions
Ch. 12 - Alcohols, Ethers, Epoxides and Thiols
Ch. 13 - Alcohols and Carbonyl Compounds
Ch. 14 - Synthetic Techniques
Ch. 15 - Analytical Techniques: IR, NMR, Mass Spect
Ch. 16 - Conjugated Systems
Ch. 17 - Aromaticity
Ch. 18 - Reactions of Aromatics: EAS and Beyond
Ch. 19 - Aldehydes and Ketones: Nucleophilic Addition
Ch. 20 - Carboxylic Acid Derivatives: NAS
Ch. 21 - Enolate Chemistry: Reactions at the Alpha-Carbon
Ch. 22 - Condensation Chemistry
Ch. 23 - Amines
Ch. 24 - Carbohydrates
Ch. 25 - Phenols
Ch. 26 - Amino Acids, Peptides, and Proteins

Birch Reduction

See all sections
Sections
Electrophilic Aromatic Substitution
Benzene Reactions
EAS: Halogenation Mechanism
EAS: Nitration Mechanism
EAS: Friedel-Crafts Alkylation Mechanism
EAS: Friedel-Crafts Acylation Mechanism
EAS: Any Carbocation Mechanism
Electron Withdrawing Groups
EAS: Ortho vs. Para Positions
Acylation of Aniline
Limitations of Friedel-Crafts Alkyation
Advantages of Friedel-Crafts Acylation
Blocking Groups - Sulfonic Acid
EAS: Synergistic and Competitive Groups
Side-Chain Halogenation
Side-Chain Oxidation
Birch Reduction
EAS: Sequence Groups
EAS: Retrosynthesis
Diazo Replacement Reactions
Diazo Sequence Groups
Diazo Retrosynthesis
Nucleophilic Aromatic Substitution
Benzyne
Additional Practice
EAS: Sulfonation Mechanism
EAS: Gatterman–Koch Reaction
EAS: Total Benzene Isomers
EAS: Polycyclic Aromatic Hydrocarbons
EAS: Directing Effects
Resonance Theory of EAS Directing Effects
Activated Benzene and Polysubstitutions
Clemmensen Reduction
EAS: Dueling Benzenes
Hydrogenation of Benzene
EAS: Missing Reagent
EAS: Synthesis
Diazonization of Aniline
Diazo Coupling Reactions
SNAr vs. Benzyne
Aromatic Missing Reagent
Aromatic Synthesis
Aromatic Retrosynthesis
EAS on 5-membered Heterocycles
Johnny Betancourt

Birch reduction reduces aromatic compounds to isolated dienes. Substituents attached to the ring can affect the orientation of the double bonds. 

Overview: 

How exactly does Birch reduction work? Good news! It uses reagents very similar to those in a reaction you’ve already learned: dissolving metal reduction (AKA metal-ammonia reduction of alkynes). Before we cover the effects substituents have, let’s cover the basics. Birch reduction uses two equivalents of lithium or sodium metal, two equivalents an alcohol, and liquid ammonia. The only major difference between this reagent set and dissolving metal reduction is the presence of alcohol.

Mechanism: 

The mechanism will look very similar to that of dissolving metal reduction, so strap in! The first step is sodium’s (or lithium’s) donation of an electron to the benzene, and that forms the radical anion. The resulting lone pair then pulls a hydrogen from the alcohol, resulting in a conjugated radical. Another equivalent of sodium donates an electron, and then the resulting lone pair pulls a hydrogen from another equivalent of alcohol. This mechanism produces an isolated diene, forgoing the more stable conjugated diene. 

Birch-reduction-mechanismBirch reduction mechanism
Substituent Effects:  

That’s all fine and dandy, but what happens when there are substituents on the benzene? Remember that benzene substituents can be divided into two categories: electron-donating groups (EDGs) and electron-withdrawing groups (EWGs). The methoxy group on anisole would be an EDG, and the chlorine on chlorobenzene would be an EWGEDGs and EWGs will orient the double bonds differently. EDGs attach themselves to the diene, and EWGs


Birch-reduction-generic-substituents

Birch reduction generic substituents

Above is the general reaction scheme with generic substituents. Below is the reaction scheme with toluene, aniline, nitrobenzene, and acetophenone.


Birch-reduction-specific-examplesBirch reduction specific examples

So, that’s about it! Good luck studying. Remember that I’ve got tons of videos on this topic and everything else you need in Organic Chemistry.


Johnny Betancourt

Johnny got his start tutoring Organic in 2006 when he was a Teaching Assistant. He graduated in Chemistry from FIU and finished up his UF Doctor of Pharmacy last year. He now enjoys helping thousands of students crush mechanisms, while moonlighting as a clinical pharmacist on weekends.