This presentation will give a solid idea about phase transfer catalyst and ultrasound in organic chemistry. both sono_chemistry and phase transfer catalysis widely used in organic synthesis. let explore more in slide

1. Topics
Phase-transfer catalyst
ultrasound in organic reactions

2. Phase transfer catalyst
Phase-transfer catalyst (PTC) is a catalyst that facilitates the
Migration of a reactant from one phase into another phase where
reaction occurs.
Chem. Rev. 2018, 118, 18, 8770–8785
Phase-transfer catalysis (PTC) has been widely used for the synthesis of
organic compounds for more than five decades.

3. Why we need to use phase transfer catalyst?
2. Moreover, Phase-transfer catalysts are useful in green
synthesis by allowing water as solvent.
1. A phase-transfer catalyst enables the reaction in a
heterogeneous system between general organic compounds
soluble in organic solvents and compounds soluble in water
such as inorganic salts.
J. Pure and App. Chem., 2000,72, 7, 1399-1403.
J. Am. Chem. Soc. 1971, 93, 1, 195–199

4. Type phase transfer catalyst
 Phase-transfer catalysts for anionic reactants are often
quaternary ammonium salts. Some commercially available
phase transfer catalysts are benzyltriethylammonium chloride,
methyltricaprylammonium chloride, methyltributylammonium
chloride, and methyltrioctylammonium chloride.
Phase-transfer catalyst,Wikipedia, The Free
Encyclopedia. 2023

5. Type phase transfer catalyst
Halpern, M. (2000) , Ullmann's Encyclopedia of Industrial Chemistry.
 Organic phosphonium salts are also used, e.g.,
hexadecyltributylphosphonium bromide. The phosphonium
salts tolerate higher temperatures, but are unstable toward
base, degrading to phosphine oxide.
 Many commercially available crown ether can be found easily
and are employed as a PTC in various kinds of reactions. The
role of crown ether as PTC in polymer science are also
diversely studied.
Molecules 2021, 26(21), 6542

6. Mechanism of Phase transfer catalyst
In general, there are two immiscible phases in reaction mixture,
viz. an aqueous phase which contains a salt (a base or
nucleophile) and the other an organic phase containing the
substrate which is expected to react with the salt.
Chem. Rev. 2018, 118, 18, 8770–8785

7. When a phase transfer catalyst (usually contains a lipophilic cation) is
added to the reaction mixture, the lipophilic cation (which has
solubility in both aqueous and organic phases), exchanges anions
with the excess of anions in the salt solution.
J. Am. Chem. Soc. 1971, 93, 1, 195–199
Then a phase transfer equilibrium exists as
Once nucleophile or base comes in nonpolar (organic) media, the
displacement can take place with the product formation. The overall
mechanism can be represented as follows:

8. Advantages Phase transfer catalyst
1. Faster reactions rate
2. Higher conversions or yields
3. Lower byproducts formation
4. Reduce the need for expensive/hazardous solvents that
will dissolve all the reactants in one phase
5. Phase-transfer catalysts are especially useful in green
synthesis by allowing water as solvent.
6. PTCs can be employed in a wide variety of organic
synthesis reactions, making them a versatile tool for
chemists.
7. By enabling faster reactions, higher yields, and the use
of less expensive solvents, PTCs can significantly reduce
overall process costs.
Molecular Catalysis, 2019, 466, 212-121

9. Application phase transfer catalyst
2. Asymmetric Oxidation reaction : Epoxidation
1. Improved Williamson ether synthesis using phase transfer
catalysis
1.H. H. Freedman, R. A. Dubois, Tetrahedron Lett. 1975, 16, 3251
Matsumoto, K., Katsuki, T., Comprehensive Chirality, 2012, 5, 69-117

10. Application phase transfer catalyst
4. N-alkylation reaction
3. Carbon–Carbon σ-Bond Formation
Kenkichi Sonogashira, Comprehensive Organic Synthesis, 1991
A. Krutošóková, T. Gracza, Comprehensive Heterocyclic Chemistry III, 2008
Guoshu Xie, ... Béla Török,
Contemporary Chemical Approaches
for Green and Sustainable Drugs,
2022

11. Ultrasound in chemical reactions
 Ultrasound is sound with frequencies greater than 20 KHz.
This frequency is the approximate upper audible limit of
human hearing in healthy young adults.
 when ultrasound is used to accelerate chemical reactions in
solution. The process is called sonochemistry. Usually it uses
frequencies 20 KHz to 40 KHz.
 The influence of ultrasonic waves travelling through liquids was
first reported by Robert Williams Wood (1868–1955) and Alfred
Lee Loomis (1887–1975) in 1927.
Chem. Soc. Rev.
1997, 26, 443
J. Org. Chem. 2021, 86, 20, 13833–13856

12. Mechanism of Ultrasound’s use in reactions
These bubbles act as micro reactors that offer the opportunity of
speeding up certain reactions and also allow mechanistically
novel reactions to take place in an absolutely safe manner.
The use of ultrasound waves to create acoustic cavitation(Rapid
formation and collapse of vapor bubble within liquid), which
generates small, oscillating bubbles of gaseous substances in the
liquid phase.
Bobble formation Growth of Bobble to impulsion
J. Org. Chem. 2021, 86, 20, 13833–13856

13. Advantages of use of ultrasound in reactions
1. Ultrasound Increases the rate of reaction by
enhancing mass transfer and collision frequency.
2. It offer better selectivity of reactions by creating
unique reaction conditions
3. By promoting efficient mixing and preventing side
reactions, ultrasound can lead to higher yields of
desired products.
4. Ultrasound is a clean and non-toxic technology,
often requiring fewer and less hazardous reagents
compared to traditional methods.
5. it can reduce energy consumption by accelerating
reactions at lower temperatures.
Chem. Soc. Rev. 1997, 26, 443

14. Application of ultrasound in organic reactions
2. Accelerates the speed of some know reaction
1. C3-cyanomethylated imidazo[1,2-a]pyridines preparation
with satisfactory yields and good functional group
compatibility. Zhang, Y. Zhang, J. Zhang, Q. Wu, Synlett, 2022, 33, 264-268
B. C. Ranu, A. Hajra, U. Jana, Org. Lett., 1999, 1, 1141-1143.
W. Phakhodee, D. Yamano, M. Pattarawarapan, Synlett, 2020, 31, 703-707

15. Application of ultrasound in organic reactions
3. Alkylation and acylation reactions.
Gharat, Neha N. - Rathod, Virendra K., Sonochemical Organic Synthesis, 2020, 1-4
4. Synthesis of Z and E stilbenes
Gharat, Neha N. - Rathod, Virendra K., Sonochemical Organic Synthesis, 2020, 1-41

16. Thanks for
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