This document discusses microwave assisted synthesis. Microwaves directly heat materials through ionic conduction and dipolar polarization. Microwave heating is more homogeneous than conventional heating methods. It allows for faster reactions, higher yields, lower energy consumption, and the ability to perform solvent-free reactions. Common organic reactions that can be carried out via microwave irradiation include Diels-Alder, ester hydrolysis, and nucleophilic substitutions. Microwave systems have advanced to enable both laboratory and industrial scale organic synthesis.
3. Microwaves
Wavelenght (λ): 0.1 cm - 100 cm
Frequency (ν) : 300 MHz - 300 GHz
The Electric Field heats the
substance due to ionic
conduction and dipolar
polarization
4. Microwave vs
Conventional Heating
Convection currents
Sample mix Sample
Sample mix mix
Heat conduction Microwaveheating
Microwave irradiation
You heat what
you don’t want to
heat (flask, vessel,
reactor).
Necessity of Lower energy
heating up and consumption
cooling down
solvents for
reaction and
apparatus
5. Greenness of Microwave Synthesis
Homogeneity of heating.
Energy consumption of the synthesis
Speed of heating.
Clean, reproducible and easily automated.
Microwave heating is efficiently used to force
the organic chemical reactions!!!
Under microwave irradiations, high and intense
temperature can be achieved very quickly.
According to Arrhenius equation, K =A∙e(-Ea/R∙T)
microwaves oil bath heating mantle Higher temperature = Higher reaction rate
6. Greenness of Microwave Synthesis
Low energy consumption: homogeneity and speed of heating.
Faster reaction: minutes instead of hours or days (low energy consumption).
Atom economy: greater yield, lesser wastage.
Green solvents: H2O, EtOH, methanol and acetone are strongly responsive to
microwave.
Less or no solvent: possibility to carried out concentrated reaction. Possibility of
neat condition or supported reagents.
Rapid conditions screening: integrated on-line control guarantees safe
operations.
7. List of Organic Reactions Carried
Out by Microwave Irradiation
Reactions in liquid phase
Diels-Alder, etero- Diels Alder, Alder-Bong reactions
Synthesis and hydrolisis of esters and amides
Different aliphatic nucleophilic substitutions
Oxidation of alchol
Condensation of malonic esthers
Cyclocondensations of varius eterocycle compounds
Synthesis of organometallic compounds
Reactions in phase-transfer
Saponifications of hindered esthers
Decarboxilations
Solvent-free reactions
Aliphatic nucleophilic substitutions
Hydrolisis of esters and amides
Dehydration of alchols
Oxidation of alchols
