Synthesis of Ibuprofen intermediate using alcoholic silver nanoparticles and its kinetics: A greener approach towards drug synthesis

Article abstract of DOI:10.1016/j.cplett.2017.01.021

Silver nanoparticles (AgNPs) were prepared and tested for the activity in the catalytic reduction of 4-nitrophenol to 4-aminophenol showing to be exceptionally active. Further, using AgNPs we catalytically synthesized 1-(4-isobutylphenyl)ethanol which is

Full text of DOI:10.1016/j.cplett.2017.01.021

Accepted Manuscript
Research paper
Synthesis of Ibuprofen Intermediate using Alcoholic Silver Nanoparticles and
its Kinetics: A Greener Approach towards Drug Synthesis
Sandeep J. Pawar, Shivkumar Y. Patil, Pramod P. Mahulikar, Vishvanath S.
Zope
PII:
S0009-2614(17)30032-5
DOI:
http://dx.doi.org/10.1016/j.cplett.2017.01.021
CPLETT 34459
Reference:
Chemical Physics Letters
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Received Date:
Revised Date:
Accepted Date:
18 November 2016
20 December 2016
10 January 2017
Please cite this article as: S.J. Pawar, S.Y. Patil, P.P. Mahulikar, V.S. Zope, Synthesis of Ibuprofen Intermediate
using Alcoholic Silver Nanoparticles and its Kinetics: A Greener Approach towards Drug Synthesis, Chemical
Physics Letters (2017), doi: http://dx.doi.org/10.1016/j.cplett.2017.01.021
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Synthesis of Ibuprofen Intermediate using Alcoholic Silver Nanoparticles
and its Kinetics: A Greener Approach towards Drug Synthesis
Sandeep J. Pawar,a Shivkumar Y. Patil,a Pramod P. Mahulikar,a and Vishvanath S. Zope,b
aSchool of Chemical Sciences, North Maharashtra University, Jalgaon – 425 001, MS, India.
bDepartment of Chemistry, Moolji Jetha College, Jalgaon 425 001, MS, India.
To whom corresponds should be addressed,
Prof. Vishvanath S. Zope
Department of Chemistry,
Moolji Jetha College, Jalgaon-425 001.
Tel.: 0257-2237363, 2234381
Email ID- vszope2@gmail.com
ABSTRACT:
Silver nanoparticles (AgNPs) were prepared and tested for the activity in the catalytic
reduction of 4-nitrophenol to 4-aminophenol showing to be exceptionally active. Further,
using AgNPs we catalytically synthesized 1-(4-isobutylphenyl)ethanol which is important
drug intermediate for the widely used Ibuprofen. The rate constants were determined at
temperatures 298K, 303K, 308K, 313K, 318K, 232K correspond to 0.29 min-1, 0.37 min-1,
0.40 min-1, 0.43 min-1, 0.50 min-1, 0.68 min-1, respectively. The activation energy of AgNPs
is 23.25 KJ/mol. The number of collisions of reactants in the term of frequency factor was
found to be high 1.99 × 108 min.-1 and average heat of reaction is 26.1 KJ/mol. The
recyclability study of AgNPs in the reduction of 1-(4-isobutylphenyl)ethanone (4-IBPEON)
to 1-(4-isobutylphenyl)ethanol (4-IBPE) in six consecutive reaction cycles found to be
(0.91g, 90 %), (0.89g, 88%), (0.87g, 86%), (0.84g, 83%), (0.84g, 83%), (0.81g, 80%),
respectively. We promisingly minimize the waste generated in the synthesis of 4-IBPE by
calculation E-factor and atom efficiency and was found to 0.57 and 81.56%, respectively.
Reported experimental results were directly relevance to develop theoretical concepts.
1

Keywords: Silver Nanoparticles; Catalytic Activity; E-factor; Recyclability; Ibuprofen; 1-(4-
isobutylphenyl)ethanol.
1. Introduction
In the era of nanoscience and nanotechnology,1 nanostructured material have played
an important role in the catalytic synthesis of pharmaceutical drugs due to their high surface
area, small particle size as well as “nano-effect”2 originating from small size. Currently, a
need to develop nanostructured materials based reduction methods for the synthesis of
pharmaceutical drugs on industrial process is highly essential in order to minimize waste, and
improve E-factors and atom efficiency.3 This trend toward the green chemistry, to set high
yield of product and environmentally benign processes that ascribes the economic value to
eliminating waste. Noble metal nanoparticles (NPs) is of fundamental importance to the
pharmaceutical, chemical, dyes and pesticides industries.4,5 Amongst the NPs, silver
nanoparticles (AgNPs) increasing interest towards the better catalytic performance because of
cheap and attractive physiochemical properties. AgNPs, amongst other applications, has also
been presently exploited as a catalyst in heterogeneous catalysis reactions.6 For the synthesis
of AgNPs variety of methods have been reported including chemical reduction method in
aqueous solutions7 or non-aqueous solutions,8 template method,9 electrochemical or
sonochemical reduction method,10 photocatalytic or photoinduced reduction method,11
microwave assisted synthesis,12 irradiation reduction method,13 microemulsion method14
biochemical reduction method15 and many more. Foremost chemical reduction method in
aqueous solution is the most conventional, clean and safe method. The uncapped AgNPs
were commonly synthesized by chemical reduction method.16 AgNPs have been widely used
as catalyst in the model reaction of reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-
AP) by using NaBH4.17 The catalytic reduction of 4-NP was monitored by UV-Vis
spectrophotometer under the mild reaction condition in aqueous medium.
2

Further, 1-(4-isobutylphenyl)ethanol (4-IBPE) is the most important drug
intermediate for the synthesis of ibuprofen, a well-known non-steroidal anti-inflammatory
drug (NSAID). We efficiently overcome, the use of hazardous organic solvents18 reported so
far in the synthesis of 4-IBPE from 1-(4-isobutylphenyl)ethanone (4-IBPEON) using aqueous
ethanol which resulted in high yield of product. The E-factor (Environmental Factor) and
atom efficiency (atom Utilization) are most important phenomenon towards greener and
environmental benign synthesis.19-21 The E-Factor is the most important concept played a
major role in chemical industry, particularly in pharmaceutical industry, on the problem on
waste generation in chemical manufacture. E-Factor is defined as the mass ratio of waste to
desired product and the atom efficiency. Atom efficiency is the ratio of the molecular weight
of the desired product to the sum of the molecular weights of all materials produced in the
process.19-21
In present investigation we have reported for the first time the conventional catalytic
synthesis of 4-IBPE from 4-IBPEON by using sodium borohydride (NaBH4) in the presence
of AgNPs in aqueous ethanol (Scheme – I).
Scheme 1. Synthesis of 4-IBPE from 4-IBPEON in the presence of
AgNPs
The reaction was achieved successfully in six consecutive cycles of catalyst and
completed within 5 – 10 minutes with high yield of product. Also, we have been promisingly
reported the kinetics of AgNPs which are helpful to material chemistry researchers.
3

2. Experimental
2.1. Chemicals
All chemicals (4-nitrophenol (C6H5NO3, 99%), sodium borohydride (NaBH4, 99%), silver
nitrate, (AgNO3, 99.9%) 1-(4-isobutylphenyl)ethanone (C12H16O, 98%) and deionized water
from Milli-Q system) were purchased from Sigma-Aldrich or Spectrochem or HiMedia and
used as received.
2.2. Characterizations
The characterizations of AgNPs were collected from various instrumental techniques. The
UV-Visible absorption measurement was performed on Shimadzu UV1800
Spectrophotometer. Water as blank and reference. Transmission electron microscopy was
performed on a Philips CM-200 TEM operating at 200 kV, by depositing 20 µL of dispersed
sample onto a 300 mesh copper grid coated with carbon layer IR spectra were collected at
room temperature from Shimadzu FTIR-Affinity-1instrument in dried KBr pellets in the
range 4000 to 400 cm-1. The 1H NMR spectra at 400 MHz and 13C NMR spectra at 100 MHz
were collected from BRUKER AVANCE II Spectrometer using DMSO-d6 as solvent and
tetramethylsilane (SiMe4) as internal standard. Mass spectra (MS) of 1-(4-
isobutylphenyl)ethanol was collected from WATERS, Q-TOF MICROMASS (LC-MS)
instrument.
2.3. Synthesis of Silver Nanoparticles (AgNPs)
The AgNPs were synthesized by using chemical reduction method. In brief, 10 mL of
-3
1 × 10 M AgNO3 taken in 50 ml of beaker and kept on magnetic stirrer. Then freshly
-3
prepared ice cold 30 mL solution of 2 × 10 M NaBH4 was hastily added into AgNO3 with
vigorous stirring in which the colour change from black to orange and finally pale yellow was
4

observed. Then AgNPs solution was stirred for six hours for good stability and prepared
nano-size of AgNPs particles. Finally, prepared AgNPs were kept overnight to remove excess
hydrogen and used as a catalyst in the model after their characterization.
2.4. Typical Procedure for Catalytic Reduction of 4-nitrophenol (4-NP)
The heterogeneous catalytic reduction of 4-NP was performed at room temperature in
-2
air. In this typical reaction 1.0 mL of 5 × 10 M NaBH4 and 10 µL of AgNPs were mixed for
two minutes in 3.0 mL quartz cuvette. To this mixture 1.5 mL of 1 × 10 -4 M PNP was added
and mixed. The reaction was followed by observing the absorbance spectrum of 4-NP at 
400 nm. The 4-NP spectrum diminished at every one minute time interval and new spectrum
was observed at  300 nm is indicates that formation of new product, which was confirmed
by isosbestic points.22 This results were in good agreements with reported literatures.23 The
absorbance spectra were recorded within the wavelength range of 250 – 600 nm. Further, the
same experiment were also performed in the temperature range of 298 – 323 K to determine
the effect of temperature on the Pseudo first-order rate constant.
2.5. Synthesis of 1-(4-isobutylphenyl)ethanol (4-IBPE)
Aqueous ethanol (4.0 mL) was added in 3.0 mL of AgNPs in round bottom flask, kept
in ice bath with constant stirring. This mixture we named as “Alcoholic AgNPs”. In the
mixture 0.43 g of NaBH4 was slowly added and finally 1.0 g. of 4-IBPEON added with
constant stirring. After complete addition, the reaction mixture was removed from the ice
bath and stirring was continued at room temperature. The reaction was completed within 5 to
10 minutes and it was preliminary confirmed by thin layer chromatography (TLC). The
product was isolated using ethyl acetate as organic layer and AgNPs remained in alcoholic
layer. The solvent was removed by rotary evaporator and product was dried at room
temperature.
5

2.6. Recycling Studies
The recycling studyof AgNPs were reported so far, for the catalytic reduction of 4-NP
to 4-AP. The above (4-NP to 4-AP) recycling confines towards, used concentration of
reactant was low, the reaction was monitor by UV-Vis spectrophotometer. For the first time
we have performed the recycling study of AgNPs in the reduction of 4-IBPEON to 4-IBPE.
In detail, as discussed above (2.5), we synthesized 4-IBPE in first cycle. In second cycle in
alcoholic liquor containing AgNPs was added 1.0 g of IBPEON and 0.43 g of NaBH4 with
constant stirring at room temperature. After completion of reaction, the product was isolated
from ethyl acetate as organic layer and AgNPs remained in alcoholic layer. Finally the
solvent from the product was removed by rotary evaporator. Repeated the similar procedure
for next consecutive reaction cycles and recorded the percent yield of product in every cycles.
We conclude that the AgNPs showed good catalytic activity against poisoning of catalyst
after six consecutive reaction cycles.
2.7. Reaction Mechanism
Scheme 1 reaction mechanism: Reduction of 4-IBPEON to 4-IBPE in the presence of AgNPs.
6

In the mechanism of reduction reaction of 4-IBPEON to 4-IBPE involves the initial
adsorption of 4-IBPEON and BH4¯ ions on the catalyst surface. Due to the close vicinity of
the reacting groups on the catalyst surface, the reduction becomes practicable. The catalyst
provide surface and helps this reduction process by relaying hydride ion to from BH4¯ ions to
the 4-IBPEON to forms 1-(4-isobutylphenyl)ethanoate ion. This ion absorbs proton solvent
and finally forms 4-IBPE.
3. Results and Discussion
3.1. UV-Vis. Spectrometry of Silver Nanoparticles (AgNPs)
The synthesized AgNPs by chemical reduction method were confirmed by UV-Vis
Spectrophotometer that showed the narrow surface plasmon resonance (SPR) band at 405
nm. (Figure 1). Two different SPR were observed for AgNPs, and alcoholic AgNPs. The
black SPR was recorded before proceeding the reaction while blue SPR was recorded after
completion of all reaction cycles (after cycle 6). The broad peaks showed in inset of figure 1.
After completion of every reaction cycle UV-Vis spectra was recorded. We observed that
decrease in SPR of alcoholic AgNPs was due to the dilution of AgNPs by addition of
reactants in every reaction cycle.
7

Figure 1. UV. Vis SPR of AgNPs, black SPR before reaction and blue SPR (cycle 6) after reaction.
3.2. Morphology of silver nanoparticles (AgNPs)
The morphological study using TEM of synthesized AgNPs was carried out (Figure
2, panel a, b). It was observed that the spherical shaped rigid particles having a narrow size
distribution showed good catalytic activity and high surface area. The particles were uniform
and distinctly present in aqueous collide solution. There was no change found in morphology
of AgNPs by adding alcohol (Figure 2, panel c). It proved that the TEM image of alcoholic
AgNPs is in agreements with AgNPs and thus, it confirmed that the AgNPs showed good
stability after six consecutive reaction cycles. The average particle size of AgNPs (12 ± 0.84
nm) (Figure 2. Panel d) was confirmed by TEM image.
8

a
b
d
c
Figure 2. TEM image of AgNPs (panel a, b) and alcoholic AgNPs (panel c); panel a) and c),
inset is the selected area electron diffraction (SAED) pattern. d) Particle size of AgNPs showing
average size is about 12 ± 0.84 nm approx.
3.3. Kinetics and catalytic activity of silver nanoparticles (AgNPs)
The kinetics study was performed by using Langmuir-Hinshelwood mechanism.22
Assuming that 4-NP and NaBH4 adsorbed on the surface of AgNPs, the interaction of NaBH4
on the surface of AgNPs took place and which ultimately led to the liberation of hydrogen
and 4-NP was converted to 4-AP. In general, the rate law for 4-NP reduction by NaBH4 is
given
by
Equation(1),
(1)
In the Eq. (1) k is the pseudo-first order rate constant, calculated from Langmuir-
Hinshelwood equation given by equation (2).
9

(2)
In the Eq. (2), C0 and C are the initial and final concentrations having equivalent in
terms of (A0 and At respectively) monitor at fixed wavelength at time t, k is the pseudo-first
order rate constant for AgNPs. Hence, for the constant catalyst concentration, a plot of
ln(A0/At) with respect to time gives straight line whose slope is the k. The k also determined
at various temperatures ranging from 298 – 323 K and activation energy (Ea) of the catalytic
reduction of 4-NP to 4-AP by using AgNPs was calculated by Equation (3).
(3)
In the Equation (3), k is the pseudo-first order rate constant at temperature T, A is the
frequency factor, Ea is the activation energy, R is the universal gas constant (8.314 JK-1mol-1)
In the catalytic reduction of 4-NP to 4-AP by using NaBH4 in the presence of AgNPs the heat
of reaction ΔH for the solution phase reaction is calculated from the Equation (4).
(4)
In order to study the effect of temperature on the pseudo-first order rate constant,
(figure 3.) the reactions were also performed in the temperature range of 298 K to 323 K.
The temperature of the solution in the quartz cuvette was controlled by water circulated
peltier unit with an accuracy of temperature ± 0.30C inside the cuvette holder.
Figure 3. (Panel a, b, c, d, e, and f) Illustrate that as the temperature increases in the range
of 298K to 323K for the reduction of 4-NP rate of the reaction also increased. i.e. temperature
is directly proportional to rate of reaction. At the temperature 298 K, 4-NP reduced within 13
minutes for the AgNPs catalyzed reaction at 400 nm. Similarly for different temperatures 303
K, 308 K, 313 K, 318 K and 323 K, reduced in 10, 7, 8, 8 and 5 minutes, respectively.
Finally, we conclude that pseudo-first order kinetics was observed at all temperatures and
delay of time is reduced with increasing temperature.24-26 (See ESI Figure S1, a) The
pseudo-first order rate constants were determined by plotting ln(Ao/At) as a function of time.
10

(Figure 3, insets a, b, c, d, e and f). To know the heterogeneous catalytic mechanism of
AgNPs in the reduction of 4-NP to 4-AP, the pseudo-first order rate constants were also
determined at temperature ranging from 298K to 323K. The calculated rate constants with
respect to temperatures 298K, 303 K, 308K, 313K, 318K and 323K were found to be 0.29 S-
1, 0.37 S-1, 0.40 S-1, 0.43 S-1, 0.5 S-1 and 0.68 S-1, respectively. From this investigation the
rate constants were increased as temperature increased and also strictly follows pseudo-first
order kinetics (Table 1.).
Activation energy of metal nanostructures likely depends on the size and shape of
nanoparticles.27 For the determination of activation energy of the reaction, temperature
dependent study were performed from 298K to 323K for AgNPs catalyzed reduction of PNP
to PAP (see ESI, figure S1, a) and the pseudo-first order rate constants for AgNPs were
fitted using Arrhenius equation (Equation 3) and the activation energy was calculated using
the slope of the linear plot of ln (k) versus 1000/T (see ESI, Figure S1 panel b). The
calculated activation energy for AgNPs was found to be 23.58 KJ/mol. The activation energy
calculated for the AgNPs catalyzed conversion of 4-NP to 4-AP in this study is lowest so far,
while the
11

b
d
f
a
c
e
Figure 3. The UV-Vis plots of absorbance as a function of wavelength at temperature a 298K; b
303K; c 308K; d 313K; e 318K; f 323K for regular time intervals indicates the disappearance of peak
of 4-NP due to the catalytic reduction of 4-NP to 4-AP by using NaBH4 in presence of AgNPs; in
inset of each panel shows corresponding linear plots of ln (Ao/At) versus time. Reaction conditions:
[4-NP] = 1 × 10-4 M; [NaBH4] = 5 × 10-2 M; [AgNPs] = 2.5 × 10-4 M.
12

lowest activation energies 33.8 – 45 KJ/mol has been reported for AgNPs and AgNPs
supported different agents or composites.27-30 From the Arrhenius equation frequency factor
was determined and found to very high.1.99 × 108 per min. (Equation 3) Higher the
frequency factor proved more number of collisions of reactants. The average heat of reaction
for the reduction of 4-NP to 4-AP was found to 26.1 KJ/mol. (Equation 4). E-factor and
Atom efficiency (atom utilization) are the most important concept for metal catalyzed
reactions towards the environmental benign synthesis. In the present investigation the concept
E-factor and atom efficiency were studied for AgNPs catalyzed reduction of 4-IBPEON to 4-
IBPE (Scheme-1). E-factor was found to 0.57 and proved that very minimum of waste was
generated in the synthesis of 4-IBPE. Also, the atom efficiency was found to 81.56% and
proved that higher number of atom involved in the formation of product 4-IBPE.
Table 1. The rate constants (k), at different temperatures, the activation energy (Ea), frequency factor (A)
and average heat of reaction for AgNPs catalyzed reduction of 4-NP to 4-AP by using NaBH4
Average
Rate
Activation
energy
(Ea)/KJ/mol
Temperature
T/(K)
Frequency
factor A/min reaction
ΔH/KJ/mol
Heat of
Constant
k/min-1
298
303
308
313
0.29 ± 0.04
0.37 ± 0.03
0.40 ± 0.01
0.43 ± 0.01
AgNPs
23.58
1.99 × 108
26.1
318
323
0.50 ± 0.01
0.68 ± 0.03
Table 1, shows the kinetic evaluation of AgNPs, the rate constant was found to be
steadily increasing with temperature. At temperature 298K, 4-NP reduced in 13 minutes
while at 323K 4-NP reduced within 5 minutes, is also proves that the AgNPs were stable at
temperature 323K and reduced fastly due to the rigidity of nanoparticles reported in TEM
13

images. The activation energy (23.58 KJ/mol) was also lowered and frequency factor was
found to be very highest (1.99 × 108), which concluded that higher the collisions of reactants
in solution on the surface of AgNPs due to small particle size of AgNPs provide high surface
area and finally lower the activation energy and increase the rate constant with respective to
temperature. Finally, the heat of reaction at different temperatures was calculated and the
average of heat of reaction was found to be 26.1 KJ/mol.
In the comparative study of AgNPs (Table 2), we found the lowest activation energy with
high frequency factor and lower heat of reaction because of high catalytic activity of AgNPs.
Table 2. The comparison of AgNPs with different stabilizing agent or supporting agents, size, rate
constant, activation energy, frequency factor and heat of reaction
Rate
Activation
energy
Frequency
factor
A/min
Heat of
reaction
ΔH/KJ/mol
Size of
Nanostructures/nm
Nanoparticles
Constant
k/min-1 (Ea)/KJ/mol
AgGME30
AgDENs31
25
ND
41.00
45.7
ND
ND
ND
3.37 ± 0.6
0.0001
34 ± 2.7
AgNPs32
ND
ND
35.16
ND
ND
AgNPs#
7 - 13
0.37
23.58
1.99 × 108
26.1
ND = Not Determined. # = In this work.
3.4. Yield and Characterization of 1-(4-isobutylphenyl)ethanol (4-IBPE)
We have been demonstrated catalytic reduction of 4-IBPEON to 4-IBPE by using NaBH4
in the presence of AgNPs dispersed in dilute alcohol in the interest of well-known model
reaction for the catalytic reduction of 4-NP to 4-AP. The stability of catalyst have been
studied by recycling and found to be stable to six successive cycles in laboratory scale. The
14

reaction was practically conducted on laboratory scale in the laboratory by with 1.0 gm of 4-
IBPEON and 3 mL of AgNPs and preliminary monitored by thin layer chromatography
(TLC) and melting point. As shown in figure 4. The yield of the 4-IBPE was slightly
decreased with respect to recycling cycles and found to be (0.91g, 90 %), (0.89g, 88%),
(0.87g, 86%), (0.84g, 83%), (0.84g, 83%) and (0.81g, 80%) with respect to cycles 1 to 6,
respectively (Figure 4).
Figure 4. Percent practical yield of 4-IBPE against number of cycle count.
1
13
Lastly, the synthesized 4-IBPE was characterized by using FTIR, H NMR, CMR and
mass spectroscopy (For spectra see SI, Figure S2, S3, S4 and S5). The characterization data
of 4IBPE as given below.
Spectral data of 3. 1-(4isobutyl)phenyl ethanol (IBPE) is isolated as viscous oil; b.p. 245-
246 0C; FT-IR (KBr) cm-1: 3336 (OH), 2954-2899 (CH); 1666-1624 (C-C=C), 1H NMR (400
MHz, CDCl3,) δH: 0.88 (6H, d, J = 6.6 Hz); 1.40 (3H, d, J = 6.4 Hz), 1.83 (1H, m, CH), 2.43
(2H, d, J = 7.1 Hz CH2), 2.71 (1H, br s, OH), 4.76 (1H, q, J = 6.4 Hz CH), 7.07 (2H, d, J =
13
8.08 Hz, Ar-H), 7.21 (2H, d, J = 8 Hz, Ar-H), C NMR (400 MHz, CDCl3,) δc: 22.5 , 25.1,
30.3, 45.2, 70.0, 125.3, 129.1, 140.7, 143.3; ESI-MS: m/z = 177.13 [M - H]+, 161.09 [M-OH]
15

The result were found to be well agreement with the reported literatures to conform the
product 4-IBPE.
4. Conclusion
In summary, we have efficiently investigated the catalytic performance of AgNPs in
the reduction of 4-NP to 4-AP by using NaBH4. In the UV- Vis spectra observed isosbestic
points, recyclability of catalyst and kinetics all have to be accounted by keeping an eye on to
the published mechanism. The recyclability study of AgNPs has been reported for the first
time and investigated in the reduction of 4-IBPEON – 4-IBPE by using NaBH4 in “Alcoholic
AgNPs” and found to be in the range of very excellent to good with better yield of 4-IBPE in
each stage of total six cycles. This work useful to study the stability of AgNPs which are
withstand in the organic reaction conditions to improve the catalytic recycling and efficiency
for many applications. We also successfully determined E-factor and atom efficiency, were
proved minimization of waste generated. The costly and important drug intermediate of
Ibuprofen, 4IBPE was economically synthesized in the laboratory by environmentally benign
process. In future, attempts will made to scale up the synthesis of 4-IBPE in pilot plant by
collaboration with pharmaceutical industry. This results of the present investigation could be
helpful for material chemistry scientists as well as organic researches to design the safer
synthesis of important commonly used pharmaceutical drugs.
5. Acknowledgements
The authors would like to thank BSR-UGC, New Delhi for financial support. In addition
SAIF, Chandigarh, Punjab University for Spectroscopy characterizations, SAIF, IIT Bombay
for TEM characterization.
16

6. Supplementary Information (SI)
In the additional information containing temperature dependent catalytic reduction of 4-NP
by UV-Vis. Spectroscopy with corresponding Arrhenius plot (figure S1) and spectral data
containing IR spectra (Figure S2), 1H and 13C NMR (Figure S3, S4) and mass spectra (Figure
S5) are given in supporting information.
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Graphical abstract
19

Highlights
 Synthesised and kinetics of bare AgNPs, showed good catalytic activity in the model
reduction of 4-nitrophenol (4-NP) to 4-aminophenol (4-AP).
 Environmentally benign synthesised 1-(4-isobutylphenyl)ethanol from 1-(4-
isobutylphenyl)ethanone by using AgNPs as catalyst.
 Six times recycled AgNPs as a catalyst in the synthesis of of 1-(4-
isobutylphenyl)ethanol with high yield.
 E-factor and atom efficiency were calculated to evaluated waste generated in the
process.
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