Synthesis, characterization and catalytic activity of graphene oxide/ZnO nanocomposites

Article abstract of DOI:10.1039/c4ra05833j

This paper reports on the synthesis and use of graphene oxide/ZnO nanocomposite as a heterogeneous catalyst for the synthesis of various tetrazoles. The catalyst was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and UV-vis spectroscopy. This method has the advantages of high yields, elimination of homogeneous catalysts or corrosive acids, simple methodology and easy work up. Another important factor is the stability and recyclability of the catalyst under the reaction conditions used. This heterogeneous catalyst shows no significant loss of activity in the recycling experiments. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra05833j

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Synthesis, characterization and catalytic activity of
graphene oxide/ZnO nanocomposites
Cite this: RSC Adv., 2014, 4, 36713
a
Mahmoud Nasrollahzadeh, Babak Jalehb and Ameneh Jabbarib
*
This paper reports on the synthesis and use of graphene oxide/ZnO nanocomposite as a heterogeneous
catalyst for the synthesis of various tetrazoles. The catalyst was characterized by X-ray diffraction (XRD),
scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron
microscopy (TEM) and UV-vis spectroscopy. This method has the advantages of high yields, elimination
of homogeneous catalysts or corrosive acids, simple methodology and easy work up. Another important
factor is the stability and recyclability of the catalyst under the reaction conditions used. This
heterogeneous catalyst shows no significant loss of activity in the recycling experiments.
Received 17th June 2014
Accepted 7th August 2014
DOI: 10.1039/c4ra05833j
www.rsc.org/advances
separate the catalyst from the reaction mixture and the
impossibility of reuse it in consecutive reactions. Moreover,
Introduction
with by using inexpensive and noncorrosive heterogeneous
catalysts, chemical transformations occur, especially for
industrial processes, with higher efficiency and give better
purities of the products, and offer easier work-up, which create
economic and ecological advantages. Thus, due to safety
considerations, it is desirable to develop a more efficient and
convenient method for the synthesis of tetrazoles under
heterogeneous conditions.
The importance of tetrazole chemistry, especially for applica-
tions in coordination and medicinal chemistry, organic
synthesis and materials applications has led to signicant
research by organic chemist researchers.1
Tetrazoles are conventionally synthesized via reaction of
dangerous and harmful hydrazoic acid or azide ions with
nitriles, thiocyanates or cyanamides in the presence of homo-
geneous catalysts.1,2 Earlier reported methods for the synthesis
of tetrazoles suffered from drawbacks such as the use of
expensive, toxic and moisture sensitive reagents and stoichio-
metric amounts of homogeneous catalysts, environmental
pollution caused by formation of heavy metal waste, low yields,
harsh reaction conditions, the poor availability or difficulty in
preparing the starting materials or catalysts, tedious work-ups,
and environmental pollution caused by the formation of side
products. As a result, these drawbacks have limited tetrazoles
large scale applications in industry. Later tetrazoles were
prepared from the reaction between thiocyanates or nitriles
with NaN3 and NH4Cl as a substitute for HN3.3 However,
combining sodium azide with ammonium chloride as an acid
may yield gaseous HN3, which is potentially dangerous and
toxic. Therefore, the need for improved methods that reduce or
eliminate the use and generation of hazardous compounds is
essential.
Recently, a newly layered material-graphene oxide (GO) has
attracted much attention of scientists all over the world, since it
exhibits unique surface properties (oxygenated functional
groups on the basal planes and edge), high-specic surface
area, and easy exfoliation into monolayers under water.4 Gra-
phene oxide, a delaminated layer of graphite oxide is shown in
Fig. 1. GO consists of intact graphitic regions interspersed with
sp3-hybridized carbons containing carboxyl, hydroxyl, and
epoxide functional groups on the edge, top, and bottom surface
of each sheet and sp2-hybridized carbons on the aromatic
network.5 In addition, due to its low-cost, thermal, chemical
and mechanical stability, large specic surface area and strong
interactions with metal clusters, GO is a promising material for
catalytic applications.6 The dispersion of metal oxide or metal
nanoparticles on GO potentially provides a new way to develop
catalytic materials.6 However, only a few metal oxide or metal
nanoparticles–graphene (or graphene oxide) hybrids have been
reported and fewer studies have investigated their catalytic
properties.7 We recently published synthesis of copper nano-
particles supported on reduced graphene oxide as a highly
active and recyclable catalyst for the preparation of formamides
and primary amines.8
In addition, several syntheses of tetrazoles have been
reported in the presence of homogeneous catalysts, while less
expensive heterogeneous catalysts have less received attention.
The problem with homogeneous catalysis is the difficulty to
aDepartment of Chemistry, Faculty of Science, University of Qom, Qom 37185-369,
Iran. E-mail: mahmoudnasr81@gmail.com; Fax: +98 25 32103595; Tel: +98 25
32850953
In continuation of our researches on the synthesis of tetra-
zoles and application of heterogeneous catalysts,1,9 we report a
new protocol for the preparation of the graphene oxide/ZnO
bDepartment of Physics, Bu-Ali Sina University, Postal Code 65174, Hamedan, Iran
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Table 1 EDS data of graphene oxide/ZnO
Element
Series
Norm. C [wt%]
Atom. C [at%]
Carbon
Oxygen
Zinc
K series
K series
K series
24.70
23.20
52.10
47.80
33.69
18.51
Fig. 1 Proposed structure of graphene oxide (GO).
Scheme 1 Formation of 5-substituted-1H-tetrazoles using GO/ZnO
nanocomposite.
nanocomposite and its catalytic applications as a novel and
stable heterogeneous catalyst for the synthesis of 5-substituted-
1H-tetrazoles (Scheme 1). Environmental acceptability, Fig. 3 XRD pattern of GO/ZnO nanocomposite.
economic viability, and recyclability of the graphene oxide/ZnO
nanocomposite are the advantages of this novel catalyst.
26.1ꢀ.10a Also the other diffraction peaks of GO/ZnO nano-
composite are similar to that of pure ZnO and correspond to the
hexagonal phase of ZnO (JPCDS 36-1451).
Result and discussion
According to the XRD data, the mean crystalline size (D) of
the ZnO nanoparticles in graphene oxide/ZnO sample was
calculated by using the Debye Scherrer formula:10b
An advantage of the graphene oxide/ZnO nanocomposite cata-
lyst was that its synthesis was very simple.
0:9l
Characterization of catalyst
D ¼
(1)
b cos q
The catalyst was characterized using the powder XRD, SEM,
EDS, TEM and UV-vis spectroscopy.
˚
where l ¼ 1.54 A is the wavelength of the X-ray radiation used, q
is the Bragg diffraction angle of the XRD peak and b is the
measured broadening of the diffraction line peak at the angle of
2q, at half its maximum intensity (FWHM) in radian. As
mentioned, ZnO has hexagonal unit cell with two lattice
parameters (‘a’ and ‘c’) which can be estimated from the XRD
data by using the following equations:10b
We used energy dispersive X-ray spectroscopy (EDS) to
determine chemical composition of GO/ZnO (Fig. 2). In the EDS
spectrum of catalyst, peaks related to C, O and Zn were
observed. The atomic and weight ratios are listed in Table 1.
Fig. 3 shows the XRD patterns of the as-prepared GO/ZnO
nanocomposite. GO exhibit a (002) broad diffraction peak at
Fig. 2 EDS spectrum of graphene oxide/ZnO.
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1
pffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi
dhkl
¼
(2)
(3)
4ðh2 þ k2 þ hkÞ=3a2 þ l2=c2
l
l
pffiffi
a ¼
; c ¼
sin q002
3sin q100
where dhkl is the inter-planer distance between adjacent planes
˚
in the Miller indices (hkl), l ¼ 1.54 A is the wavelength of the X-
ray radiation used, q100 and q002 are the angles of the diffraction
peaks (100) and (002) respectively. The lattice parameters for
GO/ZnO were calculated from the XRD data by using eqn (2) and
(3). The calculated lattice parameters are listed in Table 2.
Table 2 shows that the ZnO particles are nanosized (D ¼
19.03 nm). And also dhkl, a and c lattice parameters calculated
for GO/ZnO sample are in agreement with pure ZnO (JCPDS 36-
1451), which indicates that the presence of GO does not result
in the development of new crystal orientations or change in
preferential orientations of ZnO. In addition, Fig. 4a–c shows
successively the SEM (a and b) and TEM (c) images of GO and
GO/ZnO. The light-gray thin lms are the GO sheets, and the
dark regions on the GO background are due to the presence of
ZnO particles. It can be clearly seen in Fig. 4 that the exfoliated
GO sheet was decorated with ZnO aggregates with average size
of below 30 nm. It is observed that the ZnO particles are
nanosized.
A typical UV-vis spectrum of the graphene oxide/ZnO thin
lms on glass substrates is shown in Fig. 5.
Fig. 6 shows the FT-IR spectra of the pristine GO and GO/ZnO
nanocomposite. In the FT-IR spectrum for GO, the broad peak
centered at 3431 cmꢁ1 is attributed to the O–H stretching
vibrations, 1717 cmꢁ1 (stretching vibrations from C]O), 1621
cmꢁ1 (skeletal vibrations from unoxidized graphitic domains),
1184 cmꢁ1 (C–OH stretching vibrations), and at 1050 cmꢁ1 (C–O
stretching vibrations).11a The broad peak at 3437 cmꢁ1 in the
FT-IR spectrum of the GO/ZnO nanocomposite might be
attributed to the O–H stretching vibration of absorbed water
molecules. In addition, the FT-IR spectrum of GO/ZnO shows a
peak at 431 cmꢁ1. The band at 451 cmꢁ1 corresponds to the E2
mode of hexagonal ZnO.11b
Fig. 4 SEM (a and b) and TEM (c) images of graphene oxide/ZnO
nanocomposite.
Activity of graphene oxide/ZnO nanocomposite for the
synthesis of 5-substituted-1H-tetrazole
absence of catalyst (Table 3, entry 11). However, addition of the
catalyst to the mixture has rapidly increased the formation of
5-phenyl-1H-tetrazole in high yields. As shown in Table 3, the
reaction was inuenced signicantly by the solvent employed.
Among the solvents tested, DMF proved to be the most efficient
(Table 3, entry 6). The effect of catalyst loading was probed.
Catalyst loads of 0.03 g were typically required to achieve
quantitative conversion with most substrates. The use of lower
catalyst loadings resulted in incomplete reactions (entry 8).
Increasing the amount of catalyst showed no substantial
improvement in the yield. We then used the optimal reaction
conditions (catalyst (0.03 g), aryl nitrile (2.0 mmol) and sodium
azide (3.0 mmol)) for the synthesis of 5-substituted-1H-tetra-
zoles in DMF ((5.0 mL) at 120 ꢀC) for the appropriate times and
the results are shown in Table 4. Also, to explore the preference
The catalytic behavior of the GO/ZnO nanocomposite was
studied for the synthesis of 5-substituted-1H-tetrazole.
Initially, we employed sodium azide and benzonitrile as
model substrates for the development of optimized conditions.
Control experiments show that there is no reaction in the
Table 2 Some calculated properties of the GO/ZnO nanocomposite
Lattice parameters
˚
˚
˚
Sample
2q
hkl dhkl (A) D (nm) c (A) a (A) c/a
GO/ZnO
31.900 100 2.29
34.500 002 2.601
19.03
5.202 3.248 1.601
5.207 3.250 1.602
JCPDS 36-1451 31.770 100 2.814
34.422 002 2.603
—
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Table
4
Formation of 5-substituted-1H-tetrazoles by GO/ZnO
nanocompositea
Entry
1
RCN
Product
Yieldb (%)
78
Fig. 5 A typical UV-vis absorption spectrum of the graphene oxide/
ZnO thin films on glass substrates.
2
3
82
81
4
77
5
6
7
8
9
80
78
75
67
68
Fig. 6 FTIR spectra of the graphene oxide (a) and GO/ZnO nano-
composite (b).
Table 3 Optimization of reaction conditions in the preparation of 5-
phenyl-1H-tetrazolea
Entry
Catalyst (g)
Solvent
Yieldb (%)
10
11
81
71
79
1
2
3
4
5
6
7
8
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.03)
GO/ZnO nanocomposite (0.05)
GO/ZnO nanocomposite (0.01)
ZnO (0.04)
H2O
Trace
45
46
71
67
78
78
52
MeCN
Toluene
DMSO
NMP
DMF
DMF
DMF
DMF
DMF
12
9
10
11
44
ZnBr2 (0.03)
0.0
68c
0.0d
a
Reaction conditions: nitrile (2.0 mmol), sodium azide (3.0 mmol),
DMF
b
catalyst (0.03 g), DMF (5 mL), 120 ꢀC, 30 h. Yields are aer work-up.
a
Reaction conditions: benzonitrile (2.0 mmol), sodium azide (3.0
b
mmol), catalyst (0.03 g), solvent (5 mL), 120 ꢀC, 30 h. Isolated yield.
c
d
Stoichiometric amounts are used. In the absence of catalyst at 120
ꢀC, no reaction occurred aer 30 h.
Having optimized the conditions, we explored the general
applicability of graphene oxide/ZnO nanocomposite as a
of the GO/ZnO nanocomposite over other catalysts such as catalyst for cycloaddition of sodium azide with aryl nitriles
ZnBr2 and ZnO, comparison between their catalytic activities containing electron-withdrawing or donating substituents.
was made in the preparation of 5-phenyl-1H-tetrazole as the test As indicated in Table 4, it is evident that our method is
substrate. As evidenced from Table 3, under comparable reasonably general and can be applied to several types of aryl
conditions in DMF as the solvent, GO/ZnO nanocomposite acts nitriles. In all cases the reaction gave the corresponding
as strong catalyst.
products in good to excellent yields. The products were
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characterized on the basis of their spectral (IR, NMR) and carboxylic acids. Thus, signal of the NH proton of the tetra-
melting points and compared with the literature.12–15 The zole ring (NHT) shied downeld (Fig. 9).
structure of the 5-substituted-1H-tetrazoles was in agreement
with their spectra data. The disappearance of one strong and
Catalyst recyclability
sharp absorption band (CN stretching band), and the
appearance of an NH stretching band in the IR spectra, were
evidence for the formation of tetrazoles (Fig. 7). The carbon
of the tetrazole ring can be seen at about d ¼ 150–157 ppm in
the 13C NMR (Fig. 8).16 The free N–H bond of tetrazoles (NHT)
makes them acidic molecules, and not surprisingly it has
been shown that both the aliphatic and aromatic heterocy-
cles have pKa values that are similar to the corresponding
carboxylic acids, due to the ability of the moiety to stabilize a
negative charge by electron delocalization.16 In general, tet-
razolic acids exhibit physical characteristics similar to
The catalyst recycling is an important step as it reduces the cost
of the process. Thus, the recovery and reusability of the GO/ZnO
nanocomposite catalyst was examined by applying it to the
reaction of sodium azide with 4-methylbenzonitrile under the
present reaction conditions. Aer the rst run completed, the
catalyst was separated by centrifugation, washed with water and
ethanol and dried in a hot air oven at 100 ꢀC for 2 h and
employed for the next run of the reaction. The activity of the
catalyst in ve consecutive runs revealed the practical recycla-
bility of the catalyst (Fig. 10). This reusability demonstrates the
Fig. 7 FT-IR spectrum (KBr) of 5-(4-methoxyphenyl)-1H-tetrazole.
Fig. 8 13C NMR spectrum (100 MHz, DMSO-d6) of 5-(4-methoxyphenyl)-1H-tetrazole.
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Fig. 9 1H NMR spectrum (90 MHz, DMSO-d6) of 5-phenyl-1H-tetrazole.
and homogeneous catalysts, simple methodology and easy
work-up. Compared to other catalysts used for similar purposes,
GO offers several advantages, including low cost, ease of
synthesis, and high stability to ambient conditions. In addition,
this methodology offers the competitiveness of recyclability of
the catalyst without signicant loss of catalytic activity, and the
catalyst could be easily recovered and reused for several cycles,
thus making this procedure environmentally more acceptable.
Experimental section
Fig. 10 Reusability of GO/ZnO nanocomposite for the synthesis of 5-
(4-methylphenyl)-1H-tetrazole.
All reagents were purchased from the Merck and Aldrich
chemical companies and used without further purication.
Products were characterized by different spectroscopic methods
(FT-IR and 1H NMR spectra), elemental analysis (CHN) and
melting points. 1H NMR spectra were recorded on a Bruker
Avance DRX 90 and 400 MHz instrument. The chemical shis
(d) are reported in ppm relative to the TMS as internal standard.
J values are given in Hz. IR (KBr) spectra were recorded on a
Perkin-Elmer 781 spectrophotometer. Melting points were
taken in open capillary tubes with a BUCHI 510 melting point
apparatus and were uncorrected. The elemental analysis was
high stability and turnover of catalyst under operating condi-
tion. The reusability of the catalysts is one of the most impor-
tant benets and makes them useful for commercial
applications.
Conclusions
In conclusion, we have developed an efficient and simple performed using Heraeus CHN–O-Rapid analyzer. TLC was
procedure for preparation of graphene oxide/ZnO nano- performed on silica gel polygram SIL G/UV 254 plates. X-ray
composite as an efficient, easily recoverable and reusable cata- diffraction measurements were performed with a Philips
lyst. The catalyst was characterized by SEM, XRD, EDS, TEM and powder diffractometer type PW 1373 goniometer. It was
UV-vis analysis. This catalyst demonstrated a high catalytic equipped with a graphite monochromator crystal. The X-ray
activity for synthesis of 5-substituted-1H-tetrazole in high wavelength was 1.5405 Aꢀ and the diffraction patterns were
yields. This simple synthetic method has the advantages of high recorded in the 2q range (75–15) with scanning speed of 2ꢀ
yields, elimination of toxic reagents and expensive, unstable minꢁ1. Morphology and particle dispersion was investigated by
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5-Phenyl-1H-tetrazole (Table 2, entry 1). Mp 215–217 ꢀC (lit.13
215–216 C); H NMR (90 MHz, DMSO): dH 7.99–7.53 (m, 5H),
14.17 (s, br, 1H).
scanning electron microscopy (SEM) (Hitachi-Japan-S4160) and
transmission electron microscopy (TEM) (Philips CM120). The
chemical composition of the prepared catalyst was measured by
EDS performed in SEM.
1
ꢀ
5-(4-Methylphenyl)-1H-tetrazole (Table 2, entry 2). Mp 249–
251 ꢀC (lit. Aldrich 250–253 ꢀC); 1H NMR (400 MHz, DMSO): dH
7.92 (d, J ¼ 7.8 Hz, 2H), 7.40 (d, J ¼ 7.8 Hz, 2H), 2.38 (s, 3H); 13
C
Preparation of graphene oxide (GO)
NMR (100 MHz, CDCl3): dC 155.6, 141.6, 130.4, 127.3, 121.7,
21.5.
Graphite oxide was synthesized from commercial graphite by
modied Hummers method.17 The commercial graphite
powder (10 g) was put into 230 mL concentrated H2SO4 that had
been cooled to bellow of 20 ꢀC with a circulator. Then 30 g
potassium permanganate (KMnO4) was added with stirring, so
that the temperature of the mixture was xed at bellow of 20 ꢀC.
Aer it, the temperature of the reaction was changed and
brought to 40 ꢀC and mixture was stirred at 40 ꢀC for 1 h. Then
500 mL de-ionized water was added to the mixture, causing an
increase in temperature to 100 ꢀC. Aer that 2.5 mL H2O2
(30 wt%) was slowly added to the mixture supplementary this
solution was diluted by addition 500 L de-ionized water. For
purication, the suspension was washed with 1 : 10 HCl solu-
tion (200 mL) in order to remove metal ions by lter paper and
funnel. The suspension was washed with much de-ionized
water at several times, until the ltrate became neutral to
remove remaining salt impurities. Exfoliation was performed by
sonication for 1 h.
5-(4-Methoxyphenyl)-1H-tetrazole (Table 2, entry 3). Mp 231–
233 ꢀC (lit.14 231–232 ꢀC); 1H NMR (400 MHz, DMSO): dH 7.97 (d,
J ¼ 8.6 Hz, 2H), 7.14 (d, J ¼ 8.6 Hz, 2H), 3.83 (s, 3H); 13C NMR
(100 MHz, CDCl3): dC 161.8, 155.2, 129.1, 116.7, 115.3, 55.8.
5-(3-Chlorophenyl)-1H-tetrazole (Table 2, entry 4). Mp 139–
1
141 C (lit.13 139–140 C); H NMR (400 MHz, DMSO): dH 8.06
ꢀ
ꢀ
(s, 1H), 8.02–7.99 (m, 1H), 7.65 (s, 2H).
5-(4-Chlorophenyl)-1H-tetrazole (Table 2, entry 5). Mp 261–
263 ꢀC (lit. Aldrich 260–264 ꢀC); 1H NMR (400 MHz, DMSO): dH
8.07 (d, J ¼ 8.4 Hz, 2H), 7.71–7.67 (dd, J ¼ 1.6 Hz, J ¼ 2.0 Hz, 2H).
5-(4-Fluorophenyl)-1H-tetrazole (Table 2, entry 6). Mp 178–
180 ꢀC (lit. Aldrich 180 ꢀC); 1H NMR (400 MHz, DMSO): dH 8.10–
8.07 (m, 2H), 7.45–7.40 (m, 2H).
ꢀ
5-(4-Nitrophenyl)-1H-tetrazole (Table 2, entry 7). Mp 220 C
(lit.14 220 ꢀC); 1H NMR (400 MHz, DMSO): dH 8.45 (m, 2H), 8.30
(m, 2H).
ꢀ
5-(3-Pyridyl)-1H-tetrazole (Table 2, entry 8). Mp 239–241 C
(lit. Aldrich 238–242 ꢀC); 1H NMR (400 MHz, DMSO): dH 9.20 (s,
Preparation of graphene oxide/ZnO nanocomposite
1H), 8.59 (s, 1H), 8.34 (d, J ¼ 8.0 Hz, 2H), 7.49 (s, br, 1H).
GO/ZnO nanocomposite was synthesized with weight ratio of
(1 : 1) between GO and ZnO. To synthesize GO/ZnO nano-
composite, 0.5 g dried GO was dispersed in 100 mL of water to
form GO suspension by sonication, in which a further exfolia-
tion of GO was achieved. Then, zinc acetate (Zn(CH3CO2)$2H2O,
1.1 g) and sodium hydroxide (NaOH, 0.2 g) were successively
dissolved slowly in the above GO suspension, followed by
sonication for 30 min. Then by using of reuxing method, the
ꢀ
5-(4-Pyridyl)-1H-tetrazole (Table 2, entry 9). Mp 256–258 C
1
(lit.15 255–258 C); H NMR (400 MHz, DMSO): dH 8.75 (s, 2H),
ꢀ
8.01 (d, J ¼ 5.6 Hz, 5H), 5.05 (s, br, 1H).
5-(2-Naphthyl)tetrazole (Table 2, entry 10). Mp 206–208 ꢀC
(lit.14 205–207 ꢀC); 1H NMR (400 MHz, DMSO): dH 8.69 (m, 1H),
8.15 (m, 2H), 8.07 (m, 1H), 8.00 (m, 1H), 7.61 (m, 2H).
5-Benzyl-1H-tetrazole (Table 2, entry 11). Mp 119–121 ꢀC
(lit.13 118–120 ꢀC); 1H NMR (400 MHz, DMSO): dH 15.40 (br, 1H),
7.36–7.32 (m, 2H), 7.28–7.24 (m, 3H), 4.30 (s, 2H).
ꢀ
mixture stirred at 100 C for 14 h and aer it, cooled to room
temperature naturally. Finally, the composite was ltered,
washed several times with de-ionized water, and dried at 100 ꢀC
for 24 h.
5-(4-Bromophenyl)-1H-tetrazole (Table 2, entry 12). Mp 268–
270 ꢀC (lit.13 268–270 ꢀC); 1H NMR (400 MHz, DMSO): dH 16.20
(br, 1H), 8.02–7.99 (m, 2H), 7.86–7.83 (m, 2H).
General procedure for the synthesis of 5-substituted-1H-
tetrazoles
Acknowledgements
A mixture of the appropriate nitrile (2.0 mmol), sodium azide
(3.0 ꢀmmol) and GO/ZnO nanocomposite (0.03 g) was stirred at
120 C for 30 h. Aer completion of reaction (as monitored by
TLC), the reaction mixture was cooled to room temperature, the
catalyst was separated by centrifugation, washed with water and
ethanol and the residue was diluted with ethyl acetate (35 mL)
and 5 N HCl (20 mL). The resultant organic layer was separated
and the aqueous layer was again extracted with ethyl acetate
(20 mL). The combined organic layers were washed with water,
dried over MgSO4 and evaporated under reduced pressure using
rotary evaporator to give the crude product. The residue was
puried by column chromatography to give the desired pure
products. The physical and spectral (IR, 1H NMR and 13C NMR)
data of the known products were found to be identical with
those reported in the literature.12–15
We gratefully acknowledge the Iranian Nano Council and the
Universities of Qom and Bu-Ali Sina for the support of this work.
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