Ultrasound and deep eutectic solvent (DES): A novel blend of techniques for rapid and energy efficient synthesis of oxazoles

Article abstract of DOI:10.1016/j.ultsonch.2012.06.003

The present work deals with the synthesis of novel oxazole compounds by using effective combination of ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method (NUS) and the comparative studies are provided. It was observed that applying ultrasound not only improved yields and reduced reaction times but also saved more than 85% energy as shown by energy consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact that it is bio-degradable, non-toxic, recyclable and could be easily prepared using inexpensive raw materials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES and US in organic synthesis.

Full text of DOI:10.1016/j.ultsonch.2012.06.003

Ultrasonics Sonochemistry 20 (2013) 287–293
Contents lists available at SciVerse ScienceDirect
Ultrasonics Sonochemistry
journal homepage: www.elsevier.com/locate/ultson
Ultrasound and deep eutectic solvent (DES): A novel blend of techniques
for rapid and energy efficient synthesis of oxazoles
Balvant S. Singh a, Hyacintha R. Lobo a, Dipak V. Pinjari b, Krishna J. Jarag a, Aniruddha B. Pandit b,
Ganapati S. Shankarling a,
⇑
a Dyestuff Technology Department, Institute of Chemical Technology, Matunga, Mumbai 400 019, India
b Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai 400 019, India
a r t i c l e i n f o
a b s t r a c t
Article history:
The present work deals with the synthesis of novel oxazole compounds by using effective combination of
ultrasound (US) and deep eutectic solvent (DES). The reaction was also conducted by thermal method
(NUS) and the comparative studies are provided. It was observed that applying ultrasound not only
improved yields and reduced reaction times but also saved more than 85% energy as shown by energy
consumption calculations. The advantages of using DES as reaction medium is highlighted from the fact
that it is bio-degradable, non-toxic, recyclable and could be easily prepared using inexpensive raw mate-
rials. The recyclability for DES was studied wherein it was found that ultrasound has no negative effects
on DES even up to four runs. In addition, the present work is the first report on the combinative use of DES
and US in organic synthesis.
Received 13 March 2012
Received in revised form 6 June 2012
Accepted 11 June 2012
Available online 19 June 2012
Keywords:
Oxazole
Ultrasound
Deep eutectic solvent
Choline chloride
Phenacyl bromide
Ó 2012 Elsevier B.V. All rights reserved.
1. Introduction
dures. Therefore, there is an obvious need to develop an efficient
synthetic method that would synthesize oxazoles under milder
The synthesis of substituted oxazole derivatives has attracted
much attention because of their versatile applications, including
biological activity such as antibacterial, anti-fungal [1], anti-tuber-
cular [2] and anti-inflammatory activities [3] as well as their utility
as valuable precursors in many useful synthetic transformations
[4–6]. Oxazoles also attract considerable attention in colorant
chemistry especially as scintillating compounds and as fluorescent
whitening agents for textiles [7,8].
conditions and in an environmentally benign manner.
Application of ultrasound in organic transformation has proved
to be an important tool in enhancing reaction rates and improving
yields [18,19]. It promotes the reaction under milder conditions
where drastic conditions are required conventionally. Ultrasound
functions by cavitation process that involves sequential formation,
growth and collapse of millions of microscopic vapor bubbles
(voids) in the liquid. These rapid and violent implosions generate
short-lived regions with temperatures of roughly 5000 °C, pres-
sures of about 1000 atm as well as heating and cooling rates above
10 billion degree celsius per second [20]. Such localized hot spots
can be visualized as a micro reactor in which the energy of sound
is transformed into a useful chemical form [21,22]. It follows that
ultrasound energy can activate reactant molecules that are capable
of penetrating the atmosphere of the bubble [23]. To add to this, it
has been shown that the rates of ultrasound-assisted reactions can
be improved by lowering the vapor pressure of solvents [24,25]. In
this context, non-volatile solvents like ionic liquids have been re-
ported to be used in ultrasound promoted reactions that can force
even less volatile substrates to undergo the cavitational activation
[26,27].
Although significant progress has been made towards the syn-
thesis of oxazoles, they are most commonly obtained by the reac-
tion of
a-haloketones with amides [9] or the cyclodehydration of
b-ketoamides [10]. Other methods include dehydrogenation of
oxazolines [11] and other processes such as aza-Wittig reactions
[12], Schmidt rearrangements [13], use of isocyanides [14], TosMIC
[15], intramolecular alkyne additions [16] and microwave [17].
Majority of the above stated methods suffer from many demerits
that include use of toxic reagents, volatile solvents or expensive
catalysts. The reaction conditions are also harsh for most of these
reactions and some are even related with tedious work-up proce-
⇑
Corresponding author. Address: Department of Dyestuff Technology, Institute
of Chemical Technology, N. P.Marg, Matunga, Mumbai 400 019, India. Tel.: +91 22
33612708; fax: +91 22 33611020.
Ionic liquids (ILs) are ionic compounds composed of discrete
cations and anions mostly liquid at or below 100 °C. However, ionic
liquids, especially those based on imidazole with fluorinated an-
ions, not only suffer from the demerits of being non-biodegradable,
E-mail addresses: gsshankarling@gmail.com, gs.shankarling@ictmumbai.edu.in
(G.S. Shankarling).
1350-4177/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.ultsonch.2012.06.003

288
B.S. Singh et al. / Ultrasonics Sonochemistry 20 (2013) 287–293
toxic and commercially expensive, but their production is also re-
lated to the use of large amounts of unsafe and volatile organic sol-
vents [28]. In addition, a large group of ILs is found to be
combustible [29] and moisture-sensitive. Hence, with a view to ex-
plore other non-volatile solvents derived from bio-compatible re-
sources, we present the first time use of deep eutectic solvents
(DES) in sonochemical organic synthesis.
reactions were monitored by TLC using 0.25 mm E-Merck silica
gel 60 F254 precoated plates, which were visualized with UV light.
Key intermediates, 2-bromo-1-(4-methoxyphenyl) ethanone, 2-
bromo-1-(4-nitrophenyl)ethanone and 2-bromo-1-(4-bromophe-
nyl)ethanone were prepared by bromination of their respective
acetophenone derivatives with N-bromosuccinimide (NBS) in
accordance to the reported reference [37]. The deep eutectic sol-
vent used in the present work was easily prepared from choline
chloride (1 eq) and urea (2 eq) at 80 °C by a previously reported
method [38] with 100% atom economy. The resulting viscous liquid
was used directly without any purification.
Deep eutectic solvents differ from ionic liquids since the former
can be said to be ionic mixtures rather than ionic compounds, con-
taining combination of organic halide salts (choline chloride) with
hydrogen bond donating compounds (urea, glycerol, etc.) or Lewis
acids (zinc chloride). The ability to form hydrogen bond with the
halide ion gives rise to a eutectic combination. These hydrogen-
bonding interactions lead to depression in freezing point since the
formation of eutectic is more energetically favored relative to the
lattice energies of the pure constituents [30]. Deep eutectic solvents
retain many beneficial properties of ILs like non-volatililty and
recyclability [30]. In addition, they also possess several merits over
conventional ionic liquids like: (1) ease of preparation and storage;
(2) cost-effectiveness due to inexpensive starting materials; (3) bio-
degradable nature; (4) non-toxicity; (5) no sensitivity towards
moisture and (6) high scope of industrial applicability due to the
above discussed merits. Some reports on the utility of DES in organ-
ic synthesis include acetylation of carbohydrates and cellulose [31],
selective N-alkylation [32], phthalimide synthesis [33].
2.2. Reaction scheme
The reaction scheme depicting synthesis of oxazoles from vari-
ous derivatives of phenacyl bromide and amide in deep eutectic
medium is shown in Scheme 1.
2.3. Ultrasound set-up
Ultrasound for sonochemical synthesis is generated with the
help of ultrasonic instrument set-up (horn type). The animated
representation of the set-up is given in Fig. 1. The specification
and details of the set-up, processing parameters used during the
experiments are:
Owing to the similarity of ionic liquid to DES in terms of viscos-
ity, it could be said that the application of ultrasound to DES might
create difficulty in forming cavitation owing to larger cohesive
forces due to high viscosity. However, if once formed, such a cavi-
tation will have lesser solvent interferences due to almost negligi-
ble vapor entering the cavitation bubble. Hence less violent
collapse of bubble due to cushioning effect will not be observed
as seen in the case of more volatile solvents [34]. In addition, the
reduction in solvent interference will minimize the possibility of
DES itself participating in the reaction, thereby making them ideal
as solvents for sonochemical synthesis.
Make: ACE, USA.
Operating frequency: 22 kHz.
Rated output power: 750 W.
Diameter of stainless steel tip of horn: 1.3 ꢀ 10ꢁ2 m.
Surface area of ultrasound irradiating face: 1.32 ꢀ 10ꢁ4 m2
Intensity: 3.4 ꢀ 105 W/m2.
2.4. Synthesis of oxazole derivatives 3a-e by thermal heating in DES
medium
In the present work, for the first time, organic synthesis is per-
formed using effective combination of deep eutectic solvents and
ultrasound technique. Such combination has till now been used
for electrochemical applications [35] and inorganic synthesis of
metal organic frame-work [36]. This technique proved to be a cut-
ting edge technique for synthesis of novel oxazole molecules in
comparison to use of thermal methods. Moreover, the use of DES
in sonochemical organic synthesis is quite suitable owing to their
negligible vapor pressure.
A mixture of 40-substituted phenacyl bromide (1.0 eq) and
amide derivative (1.0 eq) was added to the deep eutectic solvent
(7.0 g) with stirring. The reaction mixture was stirred at
(65 2 °C). After completion of the reaction, as monitored by thin
layer chromatography (TLC), it was found that 3.5–5 h were re-
quired for the completion consumption of the reactant 40-substi-
tuted phenacyl bromide. The reaction mass was extracted using
dichloromethane (DCM). The DCM layer was subjected to evapora-
tion under reduced vacuum to obtain the final product.
2. Materials and methods
2.5. Synthesis of oxazole derivatives 3a-e by ultrasound method in DES
medium
2.1. Materials
A mixture of 40-substituted phenacyl bromide (1.0 eq) and
amide derivative (1.0 eq) was added to the deep eutectic solvent
(7.0 g) and the mixture was stirred initially for slight mixing of
All the solvents and chemicals were procured from S D fine
chemicals (India) and were used without further purification. The
Scheme 1. Thermal and ultrasound assisted synthesis of oxazole derivatives using deep eutectic solvent as reaction medium.

B.S. Singh et al. / Ultrasonics Sonochemistry 20 (2013) 287–293
289
2.6.2. 4-(4-bromophenyl)-N-phenyl-1,3-oxazol-2-amine (3b)
UV kmax (EtOAc)/nm 302 and 341;
max/cm–1 3384 (NAH), 3101
m
(Ar. CAH), 1661 (C@N), 1585 (C@C), 1480 (C@C), 1071 (CAO), 823
(CABr); 1H NMR (300 MHz; CDCl3; Me4Si) d = 7.50–7.25 (10H, m,
CH), 4.90 (1H, s, NH); 13C NMR (300 MHz; CDCl3; Me4Si)
d = 160.7, 139.2, 131.8, 130.4, 127.8, 126.8, 121.5; EIMS m/z
(-Ph)=238.9, 240.9,
Ph = 238.
C15H11BrN2O, calculated m/z: 315, m/z-
2.6.3. 4-(4-nitrophenyl)-N-phenyl-1,3-oxazol-2-amine (3c)
UV kmax (EtOAc)/nm 248 and 347;
max/cm–1 3416 (NAH), 3146
m
Fig. 1. Schematic of ultrasound horn set-up.
(Ar. CAH), 1662 (C@N), 1606 (C@C), 1506 (ANO2), 1419 (C@C),
1348 (ANO2), 1082 (CAO); 1H NMR (300 MHz; CDCl3; Me4Si)
d = 8.26–7.19 (10H, m, CH), 4.66 (1H, s, NH); 13C NMR (300 MHz;
CDCl3; Me4Si) d = 130.8, 129.8, 128.7, 125.5, 124.1; EIMS m/
z = 238.0, 282.1, C15H11N3O3, calculated m/z: 281.3.
substrates. The reaction mixture was then placed under sonication
using an ultrasonic horn (ACE horn, 22 kHz frequency) at 40%
amplitude for required time with a 5 s ON and 5 s OFF cycle from
time t = 0 h. The temperature of the process was maintained at
35 2 °C by means of supply of water to the jacketed reactor, used
for the synthesis. The reaction was monitored by thin layer chro-
matography (TLC) by observing completion consumption of the
reactant 40-substituted phenacyl bromide. The reaction mass was
extracted using dichloromethane (DCM). The DCM layer was sub-
jected to evaporation under reduced vacuum to obtain the final
product. The reaction time was estimated by repeating the same
reaction three times. The final compound was purified by column
chromatography using toluene:ethyl acetate (8:2) as eluent.
The deep eutectic solvent could be easily isolated after extrac-
tion of product as mentioned in procedure owing to its immiscibil-
ity in DCM. The recovered DES was further used for the next run
wherein the reaction between phenacyl bromide and phenyl urea
was considered as a standard reaction.
2.6.4. [4-(4-Nitrophenyl)-1,3-oxazol-2-yl]acetonitrile (3d)
UV kmax (EtOAc)/nm 275 and 347; m
max/cm–1 3409 (NAH), 3143
(Ar. CAH), 1657 (C@N), 1571 (C@C), 1503 (ANO2), 1418 (C@C),
1324 (ANO2), 1081 (CAO); 1H NMR (300 MHz; CDCl3; Me4Si)
d = 8.25–7.26 (5H, m, CH), 4.70 (2H, s, CH2); 13C NMR (300 MHz;
CDCl3; Me4 Si) d = 129.9, 125.7, 124.2; EIMS m/z = 228.2,
C11H7N3O3, calculated m/z: 229.1.
2.6.5. 2,4-Bis(4-Nitrophenyl)-1,3-oxazole (3e)
UV kmax (EtOAc)/nm 251 and 314;
max/cm–1 3112 (NAH), 2932
m
(Ar. CAH), 1602 (C@N), 1518 (ANO2), 1412 (C@C), 1343 (ANO2),
1122 (CAO); 1H NMR (300 MHz; CDCl3; Me4Si) d = 8.40–8.10 (9H,
m, CH); 13C NMR (300 MHz; CDCl3; Me4Si) d = 190.2, 164.2,
151.0, 138.4, 134.4, 131.2, 130.9, 129.1, 128.9, 124.3, 123.8; EIMS
m/z = 313.1, C15H9N3O5, calculated m/z: 312.
3. Results and discussions
2.6. Characterization and spectral data
All oxazole compounds were characterized by FT-IR, 1H NMR,
and 13C NMR spectroscopy and mass spectrometry. 1H NMR and
13C NMR spectrums were recorded on Varian 300 MHz mercury
plus spectrometer, and chemical shifts are expressed in d ppm
using TMS as an internal standard. Mass spectral data were ob-
tained with micromass-Q-Tof (YA105) spectrometer.
3.1. Study of significance of DES in oxazole synthesis by thermal
method
The reaction parameters were optimized by synthesis of a re-
ported derivative 3a by the reaction of phenacyl bromide with phe-
nyl urea. Deep eutectic solvent and conventional organic solvents
were chosen as reaction medium. Very low yields were obtained
even after heating and refluxing the reaction mixture for several
hours in organic solvents like ethanol, chloroform, toluene and
hexane (Table 1). The yield in deep eutectic medium (choline cho-
ride and urea) was much improved in comparison to organic sol-
vents that prompted us to explore the scope for further
improvement in results using ultrasound method. This method
fetched us an improvement of yield to 86% in just 17 min. We also
tried other sonochemical synthesis of oxazoles in other deep
2.6.1. N,4-diphenyl-1,3-oxazol-2-amine (3a)
UV kmax (EtOAc)/nm 299;
m
max/cm–1 3400 (NAH), 3128 (Ar.
CAH), 1667 (C@N), 1567 (C@C), 1493 (C@C), 1447 (C@C), 1068
(CAO); 1H NMR (300 MHz; CDCl3; Me4Si) d = 7.63–7.20 (11H, m,
CH), 5.20 (1H, s, NH); 13C NMR (300 MHz; CDCl3; Me4Si)
d = 160.7, 140.0, 131.5, 129.3, 128.9, 128.7, 127.8, 127.5, 125.2;
EIMS m/z = 237.1, C15H12N2O, calculated m/z: 236.0.
Table 1
Effect of organic solvents or deep eutectic solvent (DES) in the synthesis of oxazole derivatives by NUS or US methods.
Entry
Reaction medium
Reaction conditions
Temperature (°C)
Yield (%)d
1
2
3
4
5
6
7
8
Ethanol
Chloroform
Toluene
Hexane
NUSa
NUSa
NUSa
NUSa
NUSa
USb
60
60
110
70
65
R.T.
R.T.
R.T.
–
–
10
–
60
86
15
Traces
DES (ChCl:urea)c
DES (ChCl:urea)c
DES (ChCl:glycerol)c
DES (ChCl: malonic acid)c
USb
USb
a
b
c
Reaction conditions: NUS (thermal method); phenacyl bromide (1.0 g, 5.0 mmol), phenylurea (0.76 g, 5 mmol), solvent (10 vol), reaction time = 5 h.
Reaction conditions: US (ultrasound method), phenacyl bromide (1.0 g, 5.0 mmol), phenylurea (0.76 g, 5 mmol), solvent (10 vol), reaction time = 17 min.
DES – deep eutectic solvent; ChCl – choline chloride.
d
Isolated yields.

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B.S. Singh et al. / Ultrasonics Sonochemistry 20 (2013) 287–293
Table 2
Synthesis of novel oxazole derivatives from phenacyl bromide derivatives with substituted amides by application of DES-US (deep eutectic solvent-ultrasound) blend.
Entry
Acyl bromide
Product
Reaction Time
Yield (%)
NUSd
Energy utilized
NUSd
(h)
USe
(min)
USe
86
Thermal method
(kJ/g)
Ultrasound method
(kJ/g)
3a.a
5
17
60
8.24
1.05
O
Br
N
O
NH
3b.a
3.5
3.5
15
12
45
65
89
90
6.31
6.25
0.95
0.75
Br
O
Br
Br
N
NH
NH
Br
O
3c.a
O
O2N
N
O2N
O
3d.b
4
4
16
15
62
60
83
82
7.19
6.92
1.04
0.94
O
O2N
O2N
Br
N
O2N
O2N
CN
O
3e.c
O
Br
N
NO2
O
a
b
c
All reactions were carried out with acyl bromide (1 eq), phenyl urea 2a (1 eq), DES (10 vol).
All reactions were carried out with acyl bromide (1 eq), cyanoacetamide 2b (1 eq), DES (10 vol).
All reactions were carried out with acyl bromide (1 eq), 4-nitrobenzamide 2c (1 eq), DES (10 vol).
Isolated yields of oxazoles by thermal method, reaction temperature = 65 °C.
d
e
Isolated yields of oxazoles by ultrasonic method at room temperature.
Fig. 2. Energy utilization by thermal and ultrasound methods in the synthesis of
oxazoles.
Fig. 3. Recyclability data of reaction between phenacyl bromide and phenylurea
catalyzed by combination of DES and US.
eutectic mixtures to check the room for further improvement.
However, the deep eutectic solvent of choline chloride and urea
was found to be the most effective amongst them. Thus the results
obtained, comprehend the effectiveness of the combinative tech-
nique of using ultrasound and DES rather than their individual
usage.
3.2. Synthesis of novel oxazole derivatives and energy efficiency
calculations
Novel oxazole derivatives were synthesized in DES medium by
both conventional heating and ultrasound technique to understand

B.S. Singh et al. / Ultrasonics Sonochemistry 20 (2013) 287–293
291
Scheme 2. Mechanism proposing the role of DES in synthesis of oxazole derivatives.
the merits of ultrasonication. The combination of DES and US
showed marked improvements both in terms of reaction times
and yields as depicted in Table 2. The reactions worked within just
12–16 min by use of ultrasound as against 3–5 h by thermal meth-
od (Table 2). The impact of acoustic energy results in rapid micro-
mixing thus reducing the processing time. In order to exhibit the
flexibility of this methodology for other derivatives as well, phena-
cyl bromide was derivatized and reacted with phenyl urea (entry
3b, 3c, Table 2). Novel derivatives of 2-methyl cyano oxazole (entry
3d, Table 2) and 2-phenyl oxazole (entry 3e, Table 2) were also syn-
thesized using this methodology.
We also performed energy requirement estimation for both the
methods to evaluate the energy efficiency of the processes. The re-
ported methods for energy calculation have been pioneered by
Pandit et al. [23]. However, such calculations are reported for the
first time in DES-US blended technique. The data for energy utiliza-
tion in kJ/g during reaction for all the derivatives is depicted in Ta-
ble 2 as per the energy calculations stated in Appendix A. It was
observed that ultrasound method saved more than 85% energy
with much reduced reaction time as diagrammatically represented
in Fig. 2.
urea component in deep eutectic solvent might stabilize the
oxygen atom of carbonyl group via hydrogen bonding that encour-
ages the attack of amide on phenacyl bromide derivative as well as
promotes cyclization. At the same time, it is equally important to
highlight the probable role of ultrasound in the mechanism. It is
obvious that the use of ultrasound leads to generation of micro-
scopic internal pressure within the cavitation bubbles. Due to this,
extreme microscopic conditions are created within these bubbles
such that substrates entering them are converted to highly reactive
species, thereby assisting in faster cyclization and dehydration
steps. Such an assumption has also been done in earlier reports
wherein ultrasound is used to accelerate reactions in ionic liquids
[26].
4. Conclusion
In conclusion, we have explored for the first time, a unique
combination of deep eutectic solvent and ultrasonic radiation for
clean and efficient synthesis of oxazole derivatives. Four novel
derivatives of oxazole were synthesized in just 12–17 min by the
use of ultrasound and DES as compared to conventional heating
in DES that took 3–5 h. Ultrasonic irradiation also showed a signif-
icant improvement in parameters like reaction yield and percent-
age of conversion. Deep eutectic solvent was found to promote
the reaction since no reaction was observed with conventional or-
ganic solvents. They also provide a good alternative for conven-
tional ionic liquids owing to their simple and cost-effective
preparation, bio-degradability, recyclable nature, non-toxicity.
Ultrasonic synthesis (US) method also saved considerable energy
(more than 85%) in the synthesis of oxazoles. To sum up, the meth-
od is convenient, economical, time and energy-saving, eco-friendly
and extremely efficient.
3.3. Recyclability of deep eutectic solvent
The deep eutectic solvent medium was recycled and re-used up
to four times. Reaction of phenacyl bromide with phenyl urea was
selected as the model reaction. Deep eutectic solvent recycled from
the previous run was re-used for the next run without further puri-
fication. No significant decrease in yields was obtained as shown in
Fig. 3. This indicates the fact that ultrasound does not have any
negative effect on the eutectic combination even after four runs
thus endorsing the potential of this process towards industrial
applicability.
Acknowledgements
3.4. Proposed mechanism for oxazole synthesis
Authors (BSS and HRL) are thankful to UGC-CAS for providing
fellowship and SAIF IIT-Bombay, Mumbai for recording Mass spec-
tra, 1H NMR, 13C NMR, FT-IR spectra.
Although the mechanism illustrating the role of such deep eu-
tectic solvents in oxazole synthesis is yet to be confirmed, we sug-
gest a mechanism predicting their probable role in synthesis
(Scheme 2). It is well known that the urea component in deep eu-
tectic solvent (choline chloride:urea) can catalyze reactions via
hydrogen bond catalysis [39]. Many past reports have also investi-
gated urea [40] based catalysts due to their effective hydrogen
bonding ability. Based on these assumptions, we suggest that the
Appendix A.1. Energy calculations
Following sample calculation is done on the basis of data taken
from Table 2 for the synthesis of compound 3a.

292
B.S. Singh et al. / Ultrasonics Sonochemistry 20 (2013) 287–293
¼ Mass ꢀ CP ꢀ
DT
1. Energy delivered during sonication
1a. Energy delivered during sonication = Energy required to
synthesize oxazole material.
1b. Electrical energy delivered during sonication using horn for
17 min (indicated by the power meter) = 30.70 kJ
1c. Efficiency of Horn taken for the calculation = 30% (estimated
independently using calorimetric studies)
1d. Actual energy delivered by horn during sonication = Energy
delivered during sonication using horn in 17 min ꢀ efficiency
of Horn
¼ 8:77 ꢀ 1 ꢀ ð65 ꢁ 35Þ ðCP ꢂ 1Þ
¼ 263:1 cal
¼ 1096 J ð1 cal ¼ 4:18 JÞ
2j. Total energy supplied for heating reaction mixture to 65 °C
from room temperature (35 °C)
2k. Energy supplied for heating reaction mixture to 65 °C from
room temperature
ð35 ꢃCÞ ꢀ 5 h ꢀ ð1=30Þ h ð30 min are required for coolingÞ
¼ 1096 J ꢀ 10
¼ 10960 J ¼ 10:96 kJ
¼ 30:70 ꢀ 30=100
¼ 9:21 kJ
2l. Net energy delivered during conventional method = Energy
delivered during conventional method for stirring + total
energy supplied for heating reaction mixture to 65 °C from
room temperature (35 °C)
1e. Quantity of material processed = Quantity of phenacyl bro-
mide + quantity of phenyl urea + quantity of DES
¼ 1ðgÞ þ 0:77ðgÞ þ 7ðgÞ
¼ 8:77ðgÞ
¼ 61:27 þ 10:96
¼ 72:23 kJ
1f. Net energy supplied for processing of material using sono-
chemical method = Actual energy delivered by horn during
sonication/Total reaction mass processed
2m. Net energy supplied for processing of material using con-
ventional method = Net energy delivered during conven-
tional method/quantity of material processed
¼ 9:21ðkJÞ=8:77ðgÞ
¼ 1:05ðkJ=gÞ
¼ 72:23ðkJÞ=8:77ðgÞ
¼ 8:24ðkJ=gÞ
3. Percentage of energy saved (%)
2. Energy delivered during conventional method.
3a. Net energy saved = (Net energy supplied for processing of
material using conventional method (B)) ꢁ (net energy sup-
plied for processing of material using sonochemical method
(A))/(net energy supplied for processing of material using
conventional method (B)) ꢀ 100
2a. Voltage input in overhead stirrer (Model REMI Motors RQ-
129/D Rajendra Electrical Industries Ltd., Vasai, India.
2b. Current measured using digital multimeter (KUSAM-MECO
Model 2718, Kusam Electrical Industries Ltd., Mumbai,
India) = 37 mA = 37 ꢀ 10ꢁ3
A
2c. Power input in magnetic stirrer = Voltage input ꢀ current
measured
¼ ð8:24 ꢁ 1:05Þ=8:24 ꢀ 100
¼ 87:26
¼ 230ðVÞ ꢀ 37 ꢀ 10ꢁ3ðAÞ
¼ 8:51 WðJ=sÞ
Similarly energy efficacy calculations have been carried out for
compounds 3b – 3e and tabulated in Table 2.
2d. Efficiency of magnetic stirrer taken for the calcula-
tion = 40% (estimated independently using calorimetric
studies)
References
2e. Actual power input in overhead stirrer = Power input in
magnetic stirrer (W) ꢀ 40/100
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