The Birch reduction is a chemical reaction that uses alkali metals like sodium or lithium in liquid ammonia or amines to reduce aromatic rings and conjugated dienes. This forms mainly unconjugated dihydro derivatives. Radical ions are reactive intermediates that contain an unpaired electron and a charge. Radical cations have a positive charge while radical anions have a negative charge. Radicals are atoms, molecules, or ions with an unpaired valence electron and can be generated through redox reactions, radiation, heat, electrolysis or electrical discharges. The Birch reduction mechanism involves the alkali metal donating an electron to form a radical anion which abstracts a proton to form an ion that picks up

1. BIRCH REDUCTION
Dr. Akhil Nagar
RCP-IPER

2. BIRCH REDUCTION
• Reduction of aromatic ring by alkali metals sodium or lithium in liq
ammonia or amines with ethanol as proton donor, to give mainly
unconjugated dihydro derivatives is known as BIRCH reduction.
Aromatic ring and conjugated dienes are reduced by this method
while isolated double bond are normally not affected sometimes
ethers are used as co solvents to dissolve the aromatic comp. Use
of t-butanol fulfills the dual role of proton donor and co solvents.
• Radical ion is a free radical species that carries a charge.
Radical ions are encountered in organic chemistry as reactive
intermediates and in mass spectrometry as gas phase ions. Positive
radical ions are called radical cations whereas negative radical
ions are called radical anions.

3. • In chemistry, a radical is an atom, molecule, or ion that has
an unpaired valence electron. It may be generated in a number of
ways, but typical methods involve redox reactions. Ionizing
radiation, heat, electrical discharges, and electrolysis are known to
produce radicals.
A radical is the hydroxyl radical, a
molecule that has one unpaired electron
on the oxygen atom.
The examples are triplet oxygen and triplet
carbene which have two unpaired electrons.

5. Alkynes are also reduced steriospecifically to trans alkene with sodium or
lithium in liquid ammonia and no added proton is needed.
The alkali metal donate an electron to the aromatic comp, forming the
alkali metal cation and radicle anion. The radicle anion is basic and
abstract the proton from protic solvent to give ion. This pick up another
electron to give ion. Its is quenched again by the proton to give dihydro
comp.

6. MECHANISM