The document discusses the advantages of water as a green solvent, highlighting its environmental benefits, safety, and efficiency in synthetic methodologies. It details the physical properties and structure of water that enable its function in various chemical reactions, such as Diels-Alder and Michael reactions. The conclusion emphasizes the growing importance of using water in organic synthesis for its cost-effectiveness and reduced environmental impact.

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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