water can be consider as a potentially green solvent.it is safest & least expensive solvent. organic reaction in aqueous medium.like deals alder reaction,pinacol coupling.

1. WATER –A GREEN SOLVENT
Karunya institute of technology and
science.
Department of chemistry
P.JEYAKIRUBA(PRK18CH1025)
VINAYA JOSE(PRK18CH1002)
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2. WATER : A GREEN SOLVENT...
Water is the best solvent among all the green solvents because of its
many advantages such as.....
 Environmental benefits
 Safety
 Synthetic efficiency
 Potential for new synthetic methodologies
 Cost
 Simple operation
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3. WATER – Physical properties …
 Low viscosity
 High specific heat
 High surface tension
 High dielectric constant
 Large cohesive energy density
 Internal pressure of water
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4. STRUCTURE OF WATER …
 Water has two hydrogen atoms covalently
linked to a central oxygen atom.
 Two lone pair of electrons occupy other two
sp3 orbitals.
 Structure is a distorted tetrahedron or bent
shape.
 This geometry and electronegativity of the
oxygen atom induces a net dipole moment.
 The tetrahedral bond angle is 104.5°.
 Because of the dipole moment, water can
serve as both donor and acceptor .
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5. HYDROGEN BONDING IN WATER…
• One water molecule can form 4 hydrogen
bonds with other water molecules.
• It is potential to form 4 hydrogen bonds
per water molecule that results anomalously
o high boiling point
o high melting point
o high heat of vapourisation
o high surface tension
o high cohesive energy density
• Due to hydrogen bonding, water has dual
activator property. Water can activate both
nucleophile and electrophile.
Hence it accelerates polar reactions.
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6. REACTIONS IN AQUEOUS MEDIUM…
A. DIELS – ALDER REACTION :-
It is [4+2] cycloaddition reaction between a conjugated diene (4
electron system) and a dienophile (2 electron system) to form an adduct.
B. CLAISEN REARRANGEMENT :-
The reaction involves allyl phenyl ether on heating undergo 3,3-
sigmatropic rearrangement.
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7. C. MICHAEL REACTION :-
It is reaction between an ,β-unsaturated carbonyl compound and a
compound with an active methylene group in the presence of base to form
adduct.
D. ALDOL CONDENSATION :-
Enol reacts with carbonyl compound to form a β-hydroxyl aldehyde or
ketone , followed by dehydration to give conjugated enone
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8. E. PINACOL COUPLING :-
Ketone on reaction with Mg/benzene gives 1,2-diol (pinacol).
F. STRECKER SYNTHESIS :-
The reaction of an aldehyde with ammonia followed by reaction with HCN
gives -aminonitrile intermediates which on hydrolysis gives
-aminoacid
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9. G. SUZUKI REACTION :-
The reaction between aryl halides and phenyl boronic acid to give biaryl
derivatives. It was performed in aqueous medium using in microwave
irradiation.
H. WURTZ REACTION :-
Coupling of alkyl halides with Zn in presence of water to give
hydrocarbons.
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10. I. ESTERIFICATION :-
Esterification occurs when a carboxylic acid reacts with an alcohol in
presence of acid catalyst and heat.
J. WILLIAMSONS ETHER SYNTHESIS :-
It is the reaction between phenol and aryl or alkyl chlorides to form ether.
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11. CONCULSION…
 With increasing attention towards greener approaches for organic synthesis
adaptation of greener method is the demand of modern chemistry and in
such a scenario, water is going to be the solvent of choice because of its
unique advantage.
 The use of water as solvent may not cause problems of pollution ,which is
major concern in using volatile organic solvent. Water can be readily
recycled.
 Unlike organic solvent, which are inflammable, potentially explosive and
carcinogenic, water is free of all these disadvantages and is a safe solvent.
 A special advantage is that organic synthesis in water can significantly
reduce the number of steps when designed properly .
 The use of water as a medium for organic reaction will provide economical,
health and environmental benefits….
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