The document discusses green synthesis and microwave-assisted reactions. It describes the conventional synthesis of adipic acid and catechol and provides examples of green syntheses for these compounds. It also defines microwave irradiation and lists advantages of microwave heating over conventional heating. Examples of microwave-assisted reactions discussed include Hofmann elimination, hydrolysis of methyl benzoate, and oxidation reactions using water or organic solvents.

1. EXAMPLES OF GREEN
SYNTHESIS/ REACTION
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2. GREEN SYNTHESIS OF ADEPIC ACID
• Adipic acid is bulk chemical used for production of Nylon 6,6.
• In produced chemically is more than 2 million kg.
• Conventional method of Adipic acid synthesis
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3. N20 +
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7. GREEN SYNTHESIS OF CATECHOL
It is also called as Pyrocatechol or 1,2-dihydroxybenzene
 MOLECULAR formula is C6 H4 (OH)2
 It was I st discovered by destructive distillation of Plant extract catechin. (Edgar H.
Emil, 1839)
 About 20,000 tonnes of catechol is synthesized annually
Other Names of Catechol
 2- Hydroxy phenol
 1,2-Benzene diol
1,2.- dihydroxy benzene
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9. Microwave assisted reactions in water:
Hofmann Elimination
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10. Definition of microwave
A microwave (MW) is a form of electromagnetic energy. It is defined as a
measurement of the frequency of 300 to 3000000 MHz which comes from
the lower end of the electromagnetic spectrum, corresponding to
wavelengths of 1 cm to 1 m.
The main difference between microwave energy and other forms of
radiation such as X-rays and Y-rays is that microwave energy is non-
ionizing and thus does not change the molecular structure of the
compounds, it only provides thermal activation.
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11. Advantages of microwave
heating over conventional heating
1. Microwave heating does not depend on the thermal conductivity of the vessel whereas
conventional heating depends on the thermal conductivity of the vessel.
2. Microwave heating enhanced product purities as unwanted side reactions are less compared to
conventional heating.
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12. 2. Microwave heating enhanced product purities as unwanted side reactions are less compared to
conventional heating.
3. In microwave heating, the reaction mixture is homogeneously heated whereas, in conventional
heating, heat is transferred from surface to reaction solvent and then to species, making it less efficient.
4. In microwave heating, reaction time is dramatically reduced as compared to conventional heating
.
5. Microwave heating gives us better reaction kinetics compared to conventional heating.
6. Microwave heating gives us more product yield with high purity as compared to conventional heating.
7. Microwave heating has high energy efficiency as the surrounding heat loss can be reduced as
compared to conventional heating
.
8. Microwave heating minimizes the chances of unwanted side chemical reactions compared to
conventional heating.
9. Microwave heating is modern and more reliable as compared to conventional heating.
10. Microwave heating gives high reproducibility in results as compared to conventional heating.
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13. Solvents used in the microwave-assisted synthesis
Solvents having higher dielectric constant are preferred
like water, methanol, DMF, ethyl acetate, acetone, acetic
acid, etc.
Solvents having a low dielectric constant like hexane,
toluene, carbon tetrachloride, etc. are not preferred
because they do not couple and do not get heated rapidly
under microwave irradiation.
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14. Microwave-assisted reactions in water
1. Hofmann Elimination
In this method, thermally unstable Hofmann elimination product is
synthesized using microwave irradiation. It is done in a water-chloroform
system to get a high yield.
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15. 2. Hydrolysis of methyl benzoate to benzoic acid
(Saponification)
3-Oxidation of Toluene
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16. 4. Oxidation of Alcohols
(a) Oxidation of Primary alcohols
Primary alcohols can be oxidized to carboxylic acid using sodium tungstate as a
catalyst in 30% aqueous hydrogen peroxide.
b) Oxidation of Secondary Alcohols
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17. R, R1 = Various aromatic, aliphatic, and heterocyclic groups
Secondary alcohols can be oxidized under microwave irradiation by using doped
supports like clayfen, silica manganese dioxide, clay cap, CrO3- wet alumina,
iodobenzene diacetate-alumina, CuSO4-alumina, and oxone-wet alumina.
Oxidation of linear and cyclic secondary alcohols and benzylic alcohols to
carbonyl compounds can be done under microwave irradiation conditions.
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18. 2. Microwave-assisted reactions in organic solvents
1. Diels-Alder reaction
This reaction involves 1,4-addition of an alkene (say maleic anhydride) to
a conjugated diene (say anthracene) to form an adduct of a six-
membered ring. Under usual conditions, the reaction requires a reflux
period of 90 min. However, under microwave conditions, diglyme is used
as a solvent and 80% yield of the adduct is obtained in 90 seconds.
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19. 2. Decarboxylation reaction
Conventional decarboxylation of carboxylic acids involves refluxing in quinoline in
presence of copper chromite and the yields are low. However, in the presence of
microwaves, decarboxylation takes place in a much shorter time.
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