dissolving metals and birch reduction reaction

1. SEMINAR ON
DISSOLVING METALS AND
BIRCH REDUCTION
BY
MISS. NEHA MILIND DHANSEKAR
[ MSc I ANALYTICAL CHEMISTRY]
THE INSTITUTE OF SCIENCE,
15, MADAM CAMA ROAD, FORT

2.  Dissolving metals reduction using Zn, Li, Na,
Mg under neutral and acidic condition
 Li/Na- liquid NH₃ mediated reduction { birch
reduction } of aromatic compound and
acetylene

3.  Reduction means gain of electron .
 Reduction means gain of hydrogen and loss of
oxygen.
 In reduction addition of electropositive element
takes place.
 Reduction by dissolving metals takes place by
transfer of electron from metal and a proton
donor which may be water , alcohol or an acid.

4. Sodium alcohol
• Reduces ketone to
alcohol
• Reduces ester to
alcohol [
BOUVEAULT-
BLANE reduction ]
• Reduces nitriles,
oximes & aldehydes
Sodium – liquid
ammonia
• Reduces aromatic
ring to give mainly
unconjugated
dihydroderivative [
BIRCH reduction ]
Magnesium
• Reduction of
ketones with
dissolving metals in
absence of a proton
donor lead to the
formation of
bimolecular or
dimerized product
Dissolving metals

5.  This is the easiest method for reducing ketone to
alcohols.
 The reaction is carried out by adding sodium to ketonic
compound in boiling alcohol.
 Example : 1] Reduction of cycloheptenone to give
cycloheptenol.

6.  Example : Sodium alcohol also reduces esters
to alcohols. This reaction is known as
Bouveault-Blane reaction.
 Sodium alcohol also reduces nitriles, oximes
and aldehyde.

7.  Sodium – liquid ammonia reduces aromatic
ring to give mainly unconjugated
dihydroderivative.
 General reaction :


8.  Definition : This process of particularly
reducing the aromatic hydrocarbons or
terminals double bonds in the presence of an
alkali metal [ Li, Na ] as an electron source in
liquid ammonia and alcohol as a proton donar
was discovered by Birch and is called the Birch
reduction.
 Napthalene for instance , under these
condition yield 1,4 dihydronaphthalene.
Eg.

10.  The alkali metals donates an electron to the
aromatic compound , forming the alkali metal
cation and radical anion [1]
 Radical anion is very basic and abstracts a
proton from protic solvent to give a radical [2]
 This radical picks up the another electron to
give an anion [3]
 It is quenched again by proton source (ethanol)
to give unconjugated dihydro compound [4].
The last double bond is often left unreduced in
the ring.

11.  1-napthol on reduction with Na/liq. Ammonia
gives 5,8-dihydro-1-napthol.
 Some other applications.

12.  Reduction of ketones with dissolving metal in
absence of proton donor leads to the formation
of bimolecular or dimerized products.
 The reagents for this purpose are magnesium,
magnesium-amalgam or aluminium-amalgam
 The reduction of acetone to pinacol follows the
following course-

13.  Explain dissolving metals.
Birch reduction

14.  Organic reaction mechanism Author : R. K.
Bansal
 Organic reaction mechanism and applications
Author : V. K. Ahluwalia
 Strategic applications of named reactions in organic synthesis.
Author : E. J. Corey & K.C. Nicolaou.

15. THANK
YOU.
I WISH TO EXPRESS
MY SINCERE
THANKS TO ALL MY
PROFESSORS ,
SENIORS AND MY
PARENTS .