This document discusses types of sonochemical reactions, specifically heterogeneous solid/liquid and liquid/liquid reactions, and their synthetic applications. Heterogeneous solid/liquid reactions involve solids dispersed in liquids, where ultrasound enhances reactivity by cleaning the solid surface and increasing its effective area through cavitation bubble implosions and microstreaming. Heterogeneous liquid/liquid reactions generate emulsions that increase the interfacial contact area between immiscible liquids, allowing reactions to occur more readily across phase boundaries. Several examples of synthetic applications of these sonochemical reactions are provided, including esterification, saponification, Cannizzaro reactions, and Ullmann-type coupling reactions, which see increased yields, lower temperatures, or shorter reaction

1. Department of Pharmaceutical Sciences
Rashtrasant Tukadoji Maharaj Nagpur University
Nagpur-440033
Topic : Types of Sonochemical
(Heterogeneous Liquid-liquid & Liquid – Solid Reaction)
And its Synthetic Application
Presented By-
Tahmina Khan
M. Pharm. 1st Year
(Pharmaceutical Chemistry)

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Content
• Introduction
• Types Of Sonochemistry-
Heterogenous Solid /Liquid Phase Reaction.
Heterogeneous Liquid/Liquid Phase Reaction .
• Synthetic Applications
• References

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ULTRASOUND
• Ultrasound is defined by the American National Standard Institute as
“sound at frequencies greater the 20Hz”
• Ultrasound is sound wave with frequencies higher than the upper audible
limit of human being.
• The normal range of hearing is between 16Hz to 16kHz, and ultrasound is
generally considered to lie between 20kHz to 500MHz.
• Ultrasound is no different from normal [audible] sound in its physical
properties, expect in that human cannot hear it.

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SONOCHEMISTRY
• The introduction of ultrasound in chemistry is known as sonochemistry.
• Sonochemistry is a branch of chemistry dealing with the chemical effects and
application of ultrasonic waves i.e sound with frequencies above 20KHz
(20,000 cycle per second) that lies beyond the upper limit of human hearing
through the frequencies can be extended up to 100MHz that’s especially
affects on chemical activity.

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TYPES OF SONOCHEMICAL REACTION
Types Of
Sonochemistry
Homogeneous
Liquid
Phase Reaction
Heterogeneous
Solidliquid
Phase Reaction
Heterogenous
Liquidliquid
Phase Reaction
..

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HETEROGENOUS SOLID/LIQUID PHASE REACTION -
• In heterogeneous reactions, involving solids dispersed in liquids, the overall
reactivity will depend upon the available reactive surface area.
• Ultrasonically induced enhancements in the chemical reactivity that are
observed in such heterogeneous systems are because of cleaning action of
ultrasound.
• This cleaning action causes “pitting” of the surface of the solid, which acts
both to expose new surface to the reagents and increase the effective surface
area available for reaction.

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• Two processes causes the pitting-
i. The implosion of cavitation bubbles formed from seed nuclei on the
surface.
ii. Micro streaming of a jet of solvents on to the surface when a cavitation
bubble collapses in the solvent close to it.
Example-
• There are two types of reaction involving solid/liquid interfaces :
i. Those in which the solid is a reagent and is consumed in the process, and
ii. Those in which the solid often a metal-functions as a catalyst.

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• Classic use of ultrasound with solid as reagent is the preparation of a
Grignard reagent – an organo-magnesium halide.
• A long-standing problem associated with Grignard reagent synthesis is that in
order to facilitate reaction between the organic halide and the metal in an
ether solvent all the reagents must be dry and the surface of the magnesium
must be clean and oxide free.
• Ultrasonic irradiation gives initiation in under four minutes even in damp,
technical-grade ether without the addition of activators used in conventional
synthesis

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• An example of solid metal functioning as a catalyst addition of hydrogen to
an unsaturated compound – Catalytic Hydrogenation.
• Sonication at room temperature for the total hydrogenation of
diphenylacetylene (2 hours) appear to be almost as good as those obtained
under traditional reflux conditions and are substantially better than obtained
with stirring at 25°C (6 hours)

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HETEROGENOUS LIQUID/LIQUID PHASE REACTION -
• Ultrasound generates extremely fine emulsions from mixtures of immiscible
liquids.
• One of the main consequences of these emulsions is increase in the interfacial
contact area between the liquids and increase in the region over which any
reaction between species dissolved in the liquids can take place.
• This emulsification also leads to the use of ultrasound in place of phase transfer
catalyst.
Disruption of phase boundary
(highly efficient emulsification)
At a liquid liquid interface

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• An additional feature of sonication is that the sonicated emulsion is
continuously subject to mechanical vibration – enhancing any transfer
between phases.
• A good example of this type of application is to be found in the use of a
whistle reactor to enhance the hydrolysis of commercially important oils,
fats, and waxes.
• Under Sonochemical conditions the hydrolyses can be carried out at lower
temperatures, resulting in cleaner and good yield of products.

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SYNTHETIC APPLICATIONS
1. Esterification : The esterification is generally carried out in the presence
of catalyst like sulphuric acid. Reaction requires longer time, and yields
are very low. A simple procedure for the esterification of a variety of
carboxylic acids with different alcohol at ambient temperature using
ultrasound is reported.

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2 .Saponification: Ester hydrolysis is frequently affected under aggressive
conditions. It can be conducted under milder condition when sonication is
used.
Ex : methyl 1-2,4-dimethylbenzoate on saponification (20KHz)
gives 2,4 dimethyl benzoic acid 94% compared to 15% yield by normal
process of heating with aqueous alkali (60 min).

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• Cannizzaro reaction: Under heterogeneous conditions catalyzed by
barium hydroxide is considerably accelerated by low intensity ultrasound.
The yield 100% after 10 min where as no reaction is observed without the
use of ultrasound.

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• Ullmann-type coupling reactions: The Ullmann-type coupling reaction occurs
at a lower temperature and shorter time in almost quantitative yield with probe
sonication.

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Applications of Sonochemistry
1. Sonochemistry has been used for synthesis of composites for energy storage
applications nanoparticles, gold and platinum nanoparticles etc.
2. Synthesis of Cu2O-Graphene, graphene oxide- Fe2O3for lithium ion battery
electrodes. Primary/Binary/Ternary nanocomposites which gave good specific
capacitance, power energy density and cyclic stability applicable for electrode
material in Supercapacitors:
3. Ultrasound finds its application in biomedical devices.
4. Sonoporation: Enhancement in permeation due to acoustic cavitation and
thus used for modifying the permeability of cell plasma membrane. It is
mainly used to allow the uptake of molecules like DNA into the cell.
5. Sonolysis: Application in purifying water because of formation of reactive
species when ultrasound reacts with water.

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References
1. James Clark And Duncan Macquarrie. Handbook of green chemistry and
technology;2002; 372-393.
2. Sonochemistry (Application of ultrasound in chemical Synthesis and
reactions): A Review part I; Az. J. Pharm Sci. Vol. 53, March, 2016
3. Sonochemistry Advantages and Application –A Review. Research gate
publication.

18. Thank you