The catalytic activity of titania nanostructures in the synthesis of amides under solvent-free conditions

Article abstract of DOI:10.1039/c2nj40119c

Different shapes and phases of titania nanostructures with the uniform size distribution were synthesized by hydrothermal sol-gel technique. The influence of annealing temperature on the crystalline character, size and phase of the prepared nanomaterials were evidenced from the diffraction analysis. Infrared spectroscopic analysis ensured the structural confirmation of the sulfated titania nanostructures. Catalytic activity of the synthesized nanometric materials in direct amidation of aromatic and aliphatic carboxylic acids with aromatic amines was evaluated. Among the materials studied, sulfated titania nanotubes with the anatase phase exhibited excellent catalytic activity. The employed solvent-free protocol is greener and eradicates the drawbacks associated with the hazardous solvents employed in the prevailing solution phase methodologies.

Full text of DOI:10.1039/c2nj40119c

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PAPER
The catalytic activity of titania nanostructures in the synthesis of amides
under solvent-free conditionsw
Sangaraiah Nagarajan,a Park Ran,b Poovan Shanmugavelan,a Murugan Sathishkumar,a
Alagusundaram Ponnuswamy,*a Kee Suk Nahm*b and G. Gnana kumar*c
Received (in Montpellier, France) 17th February 2012, Accepted 29th March 2012
DOI: 10.1039/c2nj40119c
Different shapes and phases of titania nanostructures with the uniform size distribution were
synthesized by hydrothermal sol–gel technique. The influence of annealing temperature on the
crystalline character, size and phase of the prepared nanomaterials were evidenced from the
diffraction analysis. Infrared spectroscopic analysis ensured the structural confirmation of the
sulfated titania nanostructures. Catalytic activity of the synthesized nanometric materials in direct
amidation of aromatic and aliphatic carboxylic acids with aromatic amines was evaluated. Among
the materials studied, sulfated titania nanotubes with the anatase phase exhibited excellent
catalytic activity. The employed solvent-free protocol is greener and eradicates the drawbacks
associated with the hazardous solvents employed in the prevailing solution phase methodologies.
Recently, nanoparticles have emerged as sustainable alter-
natives to conventional materials in organic reactions, as
1. Introduction
The booming demand for introducing amide functionality in
robust and high surface area catalyst supports due to the large
compounds from pharmaceutical, chemical and natural product
number of active sites per unit area, non-hazardous nature,
selectivity, requirement in catalytic amounts, easier reaction
sectors1 has grabbed intensive attention from all corners of the
world, in which the connotation of amide formation via the
work-up, etc. The recyclability and easier separation of the
coupling of carboxylic acids and amines is highly imperative.
solid catalysts improve their competence further.
As a consequence, newer protocols for amide bond formation
Despite the aforementioned advantages of nanoparticles,
have emerged. The most frequently and extensively employed
their usage as a catalyst in amide bond formation is relatively
prevailing methodologies involve the direct coupling of amines
new. Among the nanomaterials used, titania nanoparticles
with carboxylic acids and coupling reagents2,3 or the coupling
have been proven to be excellent catalysts8 for organic reactions
of Staudinger’s phosphazenes,4 generated from phosphines
due to their high catalytic activity, selectivity, elevated surface
area, easier separation and recyclability. Though titania has
and organic azides, with carboxylic acids5 or its derivatives6
afford carboxamide. The limitations of these methodologies
been used explicitly as a catalyst for organic reactions, a
are the use of benzene (carcinogenic) as the solvent of choice,
long reaction times5a,b and solubility problems which arise
titania nanomaterials over the organic reactions has yet to be
detailed study on the impact of textural, size and shape of
with polar starting substrates.
understood.
On the other hand, micro-wave assistance in the coupling of
Hence, here in we report the efficiency of the sulfated titania
nanoparticles and nanotubes assisted direct coupling of some
carboxylic acids with amines7 involves extremely high tempera-
tures. Hence, it has been planned to simplify the preparation
aromatic amines with various aromatic and aliphatic carboxylic
procedures of amides, which would avoid the coupling reagents
and toxic solvents via the utility of an efficient catalyst.
acids under a solvent-free approach to yield the product in just
30 min, which is noteworthy as compared to the titania
nanoparticles with long reaction times (3–12 h).5a,b
a Department of Organic Chemistry, School of Chemistry,
Madurai Kamaraj University, Tamilnadu 625 021, India.
E-mail: ramradkrish@yahoo.co.in; Tel: +91 9600868323
2. Results and discussion
b Specialized Graduate School of Hydrogen and Fuel Cell Engineering,
The texture, shape, size and phase of the titania nanostructured
Chonbuk National University, Jeonju 561-756, Republic of Korea.
materials were effectively tuned by a simple hydrothermal
sol–gel technique. They were characterized by transmission
electron microscopy (TEM), XRD, FTIR, TGA, surface analyzer
and catalytic activity of the prepared nanostructured materials
in direct amidation is discussed vide infra.
E-mail: nahmks@chonbuk.ac.kr; Fax: +82 63 270 2306
c Department of Physical Chemistry, School of Chemistry,
Madurai Kamaraj University, Tamilnadu 625021, India.
E-mail: kumarg2006@gmail.com; Tel: +91 9585752997
w Electronic supplementary information (ESI) available. See DOI:
10.1039/c2nj40119c
c
1312 New J. Chem., 2012, 36, 1312–1319
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2.1. Morphological images
Fig. 1 exhibits morphological TEM images of the synthesized
titania nanoparticles. Fig. 1a clearly reveals the homo-
geneously distributed titania nanoparticles with diameters of
8–10 nm. The alkoxide precursor was easily hydrolyzed in the
water medium and polymerized into a three-dimensional oxide
network. Then the three-dimensional network was subjected
to the condensation reaction which yielded the titania
nanoparticles. Thus, it has been concluded that the titania
nanoparticles are produced by the hydrolysis of alkoxide,
condensation of the hydrolyzed species, nucleation and growth
of primary particles, aggregation of the primary particles
and precipitation of large clusters.9 These reactions can be
schematically represented as follows:
Fig. 2 TEM images of the titania nanotubes synthesized from
(a) as-synthesized (b) 800 1C calcined titania nanoparticles.
the titanate nanotubes is exchanged by H+ which produces the
hydrogen titania nanotubes. The hydrate nanotubes are
dehydrated by heat treatment, which leads to the formation
of pure titania nanotubes. In other words, the nanotubes
Ti(OR)4 + 4H2O - 2Ti(OH)4 + 4ROH
(1)
(2)
obtained through the hydrothermal treatment of TiO2 and
2À
NaOH, had walls formed by Ti3O7
(titanate) and the
Ti(OH)4 - TiO2 xH2O + (2 À x) H2O
interlamellar region would be occupied by H+ ions. Though
the diameter of the two kinds of nanotubes is of 3–6 nm, the
titania nanotubes prepared from 800 1C calcined titania nano-
particles exhibited a bundle like structure, as shown in Fig. 2b.
It may be due to the larger size of its host titania nanoparticles.
The as-synthesized 8–10 nm sized nanoparticles were subjected
to thermal treatment and an increase in the temperature
gradually increased the size of the titania nanoparticles, as
shown in Fig. 1b–d. An increase in the temperature increases
the aggregation of the prepared nanoparticles which in turn
leads to the particle size increase.10
2.2. X-Ray diffraction studies
The uniform nanotubular structure with a high dispersion in
lengths and small diameters were obtained for the synthesized
titania nanotubes as shown in Fig. 2a. The tubes were found
to be about several hundred nanometers in length and 3–6 nm
in diameter. Sodium hydroxide played a major role in the
formation of the tubular structure. The synthesized titania
particles reacted with sodium hydroxide and lead to a layered
alkali titanate. These layered crystals were very thin and were
easily exfoliated into individual nanosheets that were highly
anisotropic in two-dimensions. Titania sheets were composed
of [TiO6] octahedra sharing edges with each other and formed
a ribbon structure. Under the high pressure and high temperature,
the layered structure rolled up into nanotubes due to the
surface tension.11 During the acid treatment process, Na+ in
Fig. 3 exhibits the diffraction patterns of the synthesized
titania particles. The crystalline character of the prepared
nanoparticles gets increased with an increase in the temperature.
The as-synthesized titania nanoparticles exhibited an anatase
phase and were calcined at different temperatures for the phase
transformation. Lower temperatures, i.e., 400 1C, does not
provide feasibility for the phase transformation (Fig. 3b). The
particles annealed at the intermediate temperature, i.e., 600 1C,
exhibited rutile and anatase phases (Fig. 3c). The high intensity
peaks found at 2y = 25.31 and 27.301 for the 600 1C calcined
titania particles (Fig. 3c) correspond to the (101) and (110)
planes of the anatase and rutile phases, respectively.12,13 It
suggests that phase transition from the anatase to the rutile
phase gets started at this temperature and the residual anatase
phase still exists up to the temperature of 600 1C. But at a higher
temperature (800 1C), the anatase residuals were completely
removed from the prepared materials, i.e., anatase phase was
completely transformed into the rutile phase (Fig. 3d).
Two possible mechanisms, such as the spatial disturbance of
the oxygen ion framework and the shifting of the majority of
Fig. 1 Transmission electron microscopic images of the titania nano-
particles (a) before annealing, and after annealing at (b) 400 1C, (c) 600 1C,
and (d) 800 1C.
Fig. 3 XRD patterns of the (a) as-synthesized, and annealed at
(b) 400 (C) 600 and (d) 800 1C titania nanoparticles.
c
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the Ti4+ ions by breaking two of the six Ti–O bonds to form
new bonds were involved in the transformation of the anatase
to the rutile phase.14 Increments in the temperature increased
the aggregation or induced contact between the anatase
particles and transformed the anatase grains into a large rutile
grain. The nucleation and growth can also occur in the bulk or
on the surface of a large anatase grain. The growth of the rutile
grain may happen when a rutile crystallite comes into contact
with an anatase crystallite forming a larger rutile crystallite or
when two rutile nuclei merge together. The nucleation and
growth of the prepared titania nanoparticles effectively occurred
at 800 1C. It also suggests that after the nucleation processes
the growth process started immediately. Since the titania
nanotubes were produced from the titania particles, the phase
of the titania nanotubes purely depend on their host titania
nanoparticles (Fig. 4a and b) and the phase transformation did
not occur for the titania nanotubes. There were no morpho-
logical and diffraction changes observed between the bare and
sulfated titania nanoparticles and nanotubes.
Fig. 5 Thermogravimetric analysis of (a) bare and (b) sulfated titania
nanotubes.
bare titania nanotubes due to its high hydrophilic character.
Though the prepared nanotubes exhibited continuous weight
losses, the lower weight loss observed from the spectrum
guaranteed its higher thermal stability.
2.3. Structural characterization
Structural confirmation of the sulfated titania nanotubes was
characterized by infrared spectroscopy (see ESIw) and the
obtained peaks are assigned as follows: intensive bands
observed at 3437 and 1636 cmÀ1 are attributed to the stretching
vibration of hydroxyl groups and adsorbed water molecules,
respectively.15 The SQO stretching of the sulfated titania
nanotubes were found at 1052 and 1132 cmÀ1, which represent
the successful implantation of sulfonic acid moieties over the
titania nanotubes. Significant bands observed in the region
of 400–1000 cmÀ1 represent the Ti–O framework stretching
frequencies.
2.5. Textural properties
The specific surface area of the prepared titania nanoparticles
are given in Table 2. The as-synthesized nanoparticles exhibited
higher surface areas than those of the calcined samples due to
their smaller crystallite size.16 But an increase in the tempera-
ture effectively increased the crystallite size of the prepared
materials which decreases the surface area of the corres-
ponding materials. As shown in Table 2, the surface area
decreased for the calcined samples. The conversion of titania
nanoparticles into titania nanotubes effectively increases the
surface area and is purely attributed to the tubular shape of
the prepared sample. The sulfonation process effectively
increased the surface area of the corresponding nanomaterials
and its influence on catalytic activity will be discussed later.
2.4. Thermal behavior
Fig. 5 depicts the thermogravimetric analysis of bare and
sulfated titania nanotubes. The prepared samples exhibited
continuous weight losses at lower temperatures and continued
at the higher temperatures. The bare titania nanotubes (Fig. 5a)
exhibited a significant weight loss at 80–100 1C and this is
attributed to the evaporation of physisorbed and interlayer
water molecules. The sulfated titania nanotubes (Fig. 5b)
exhibited two significant weight losses at 80–100 1C and
300–345 1C and are attributed to the evaporation of physi-
sorbed and interlayer water molecules and the decomposition
of sulfonic acid moieties, respectively. The sulfated titania
nanotubes exhibited a lower thermal stability than that of
2.6. Catalytic activity of the titania nanostructured materials
on amide synthesis
The aim of the present work is to investigate and characterize
the activity of nanometric titania particles as the heterogeneous
catalyst for direct amidation. To investigate the catalytic activity
of the titania nanoparticles, phenyl acetic acid 1a has been chosen
as a representative substrate and was reacted with aniline at
110 1C for 30 min under solvent-free conditions.
In the absence of a catalyst (Table 1, entry 1), amide was
formed in 45% yield. The catalyst amount was varied over a
range of 0–30 wt% of total mass of the reactants. Increasing
the catalyst concentration increases the number of active sites.
The increased number of active sites promote the number of
contact sites between the catalyst and substrates, and this gets
reflected in the yield of the amide formation. Table 1 indicates
that the yield of the amide formation is directly proportional
to the amount of catalyst used and reaches a constant at about
24 wt%. It has been assumed that the active sites which has
been provided by the catalyst up to 24 wt% has been effectively
used by the substrates and beyond which the active sites are
not used up by the organic substrates. From the obtained values,
Fig. 4 XRD pattern of titania nanotubes prepared from the (a) synthe-
sized titania nanoparticles, and the (b) 800 1C calcined titania nanoparticles.
c
1314 New J. Chem., 2012, 36, 1312–1319
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Table 1 Screening of wt% of the catalyst in the synthesis of
N,2-diphenylacetamide
by EDX analysis (Table 2). The sulfur content of the calcined
titania nanoparticles is decreased as compared to the
as-synthesized titania nanoparticles, which is due to their
larger size and lower surface area. A higher sulfur content
was obtained for the titania nanotubes prepared from the
as-synthesized titania nanoparticles than for the as-synthesized
titania nanoparticles, and this is purely attributed to their high
surface area. Since the surface to volume ratio is higher for the
nanotubes as compared to the nanoparticles, the nanotubes
adsorbed higher amounts of sulfonic acid moieties. Hence, the
sulfated titania nanotubes exhibited a higher sulfur content
and this gets reflected in the yield of amide formation, the best
affording 98% yield. The titania nanotubes prepared from the
as-synthesized titania nanoparticles exhibited a higher number
of hydroxyl groups over their surfaces and exhibited a high
hydrophilic character. However, the titania nanotubes prepared
from the calcined titania nanoparticles lost the hydroxyl groups
from their surfaces due to the calcination process, which yielded
a lower hydrophilic nature. Effective sulfonation could be
achieved only when the proper hydrophilic compatibility was
maintained between the heat matrix and the sulfuric acid. This
was more effectively satisfied by the titania nanotubes prepared
from the as-synthesized titania nanoparticles than by the titania
nanotubes prepared from the calcined titania nanoparticles due
to the higher number of hydroxyl groups.
Entry
Concentration of catalyst (wt%)
Yielda (%)
1
2
3
4
5
6
7
8
0
10
15
20
22
24
26
30
45
61
67
71
74
77b
77
77
a
b
Isolated yield. Optimized wt% of catalyst.
24 wt% has been chosen as minimum concentration of the
catalyst for effectual amide formation and has been used for
further studies.
In the study, direct amidation was investigated with and
without catalyst at 110 1C, the reaction time being 30 min.
Also interestingly the nature of the catalyst employed had an
impact on the yield of the product. Replacing the as-synthesized
nanoparticles with the 800 1C calcined nanoparticles (Table 2,
entry 3) had no promising improvement as it afforded only
71% of the amide. This observation is purely attributed to the
calcined particles having lower surface areas, as influenced by
their larger particle sizes. The other calcined (400 & 600 1C)
particles also exhibited lower catalytic activities due to their
larger particle sizes (data not shown). However, the titania
nanotubes increased the yield of amide formation due to
its high surface area achieved via its tubular structure. The
surface area of the catalyst played a vital role in determining
the yield of amide formation. The increased surface area
provides a higher number of active sites and induces higher
contact between the catalyst and substrates. In addition, the
sulfonation (sulfur content) of catalysts also plays a role in
determining the yield of a reaction (Table 2). The sulfur
content of the studied titania nanostructures has been measured
The above screening revealed that both the sulfated titania
nanoparticles (Table 2, entry 5) and the nanotubes (Table 2,
entry 6) exhibited very good catalytic activity compared to the
conventional reaction (absence of a catalyst) (Table 1, entry 1).
In particular, the sulfated titania nanotubes with the highest
surface area was found to be the best catalyst, affording 98%
of the amide in just 30 min (Table 2, entry 5). In the present
study, the rate of amidation is enhanced prominently by using
sulfated titania nanotubes compared to a recent report on
amidation catalyzed by titania nanoparticles8 wherein the
reaction time has been reported to be 3 h.
Subsequently, the reusability of the sulfated titania nano-
tubes was established and summarized in Table 3. The sulfated
titania nanotubes allowed for a robust recycling capability,
with well-retained activity of 80% even after the sixth cycle
under the same reaction conditions. An increase in the number
Table 2 Effect of titania nanocatalysts for the formation of N,2-diphenylacetamide
EDX Elemental analysis(%)
Surface area
Yielda
(%)
Entry
Catalyst
Phase
(m2 gÀ1
)
Ti
O
S
1
2
As-synthesized titania nanoparticles
Nanotubes produced from as-synthesized
titania nanoparticles
Anatase
Anatase
229
298
35.44
35.38
64.56
64.62
—
—
77
81
3
4
Titania nanoparticles calcined at 800 1C
Titania nanotubes prepared from 800 1C
calcined titania nanoparticles
Rutile
Rutile
22
56.7
35.80
35.88
64.20
64.12
—
—
71
74
5
6
7
Sulfated titania nanoparticles
Sulfated titania nanotubes
Sulfated titania nanoparticles prepared from
800 1C calcined titania nanoparticles
Sulfated titania nanotubes prepared from
800 1C calcined titania nanoparticles
Anatase
Anatase
Rutile
252
319
38
34.64
34.34
34.88
64.11
63.7
64.23
1.25
1.96
0.89
83
98
75
8
Rutile
43.6
34.74
64.17
1.09
79
Reaction conditions: phenylacetic acid (200 mg, 1.4 mmol), aniline (136 mg, 1.4 mmol) and catalyst (24 wt%) for 30 min in preheated glycerol bath
(110 1C–120 1C).a Isolated yield.
c
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Table 3 Catalyst reusability and sulfur content in amide synthesis
Table 4 Sulfated titania nanotubes catalyzed amide syntheses at 110 1C
% Yield of
N,2-diphenylacetamide
Sulfur
content (%)
Entry
Amine
Acid
Amide
Yield (%)
Entry
Recycle no.
1
2
3
4
5
6
7
Fresh
98
94
90
87
85
83
80
1.96
1.82
1.67
1.53
1.38
1.25
1.12
First recycle
Second recycle
Third recycle
Fourth recycle
Fifth recycle
Sixth recycle
1
75
2
3
98
75
of cycles detaches the sulfonic acid moieties, i.e., loss of
sulfonic acid moieties from the titania nanotubes, as revealed
from the EDX analysis (Table 3). A gradual decrease in the
sulfur content decreases the catalytic activity of the sulfated
titania nanotubes. In addition, a slight increase in the particle
size and porosity coverage of the titania nanostructures over
the repetitive cycles decreases the surface area, which reflects
in the gradual decrement of the amide formation yield.
In continuation of the above preliminary optimization, the
broad scope of the sulfated nanotubes as catalyst was estab-
lished by synthesizing structurally diversified amides which are
depicted in Table 4. The products were interpreted by 1H and
13C NMR (ESIw).
4
5
93
85
3. Conclusion
The impact of the texture, shape, size and phase of the titania
nano-materials in catalyzing the direct amidation of aromatic
and aliphatic carboxylic acids with some aromatic amines
under solvent-free conditions has been examined. Although
all of them exhibited good catalytic activities compared to the
catalyst-free conditions, the sulfated titania nanotubes were
found to be the best catalyst and hence they were used to
synthesize a variety of amides. The catalytic activity was very
promising and affords the amides in good to excellent yields in
short reaction times at relatively lower temperature. Thus, the
study conveys the fact that the sulfated titania nanotubes are
an efficient catalyst as compared to other corresponding
nanosized materials in amide synthesis via a solvent-free green
protocol eradicating the limitations associated with the hazardous
solvents used in the prevailing solution phase protocols.
6
77
7
8
87
81
4. Experimental
9
92
94
4.1. Characterizations
All chemicals and solvents were of commercially high purity
grade purchased from Acros Organics Synthesis Pvt. Ltd. and
Sigma-Aldrich Ltd, India. Melting points (mp) were obtained
on electro-thermal apparatus and are uncorrected. Conventional
transmission electron micrographs were recorded on a JEOL
JEM-2010 transmission electron microscope equipped with an
energy-dispersive X-ray spectroscopy (EDX). X-Ray diffraction
patterns of the prepared materials were characterized using
a (D-Max-3A, Rigaku XRD) diffractometer. FT-IR spectra
of the sulfated titania nanotubes was recorded between
400–4000 cmÀ1 transmittance mode using a Jasco FT-IR
spectrophotometer. Textural properties of the prepared materials
10
11
12
95
75
c
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Table 4 (continued )
method. This procedure was repeated until the washing
solution reached a pH o 7.
Entry
Amine
Acid
Amide
Yield (%)
4.4. Acidification of titania nanoparticles and nanotubes
For the sulfonation process, the freshly prepared titania
nanoparticles and nanotubes were impregnated in 0.5 M of
sulfuric acid for 24 h at room temperature. Then the materials
were centrifuged and then dried at 100 1C. The samples were
washed with deionized water, and were subsequently separated
via the centrifugation method. This procedure was repeated
until the washing solution reached a pH o 7.
13
91
14
15
86
79
4.5. Typical procedure for the preparation of amides
A mixture of phenylacetic acid (200 mg, 1.4 mmol), aniline
(136 mg, 1.4 mmol) and catalyst (80 mg, 24 wt% (W/W) in a
microwave vial (10 mL), and was heated at 110 1C for 30 min
in a preheated glycerol bath. Then the mixture was diluted
with ethylacetate (10 mL) and centrifuged to remove the
catalyst. The filtrate was washed with 10% NaHCO3 (10 mL)
and dried over anhydrous magnesium sulphate. The solvent
was then removed under reduced pressure to give the amide
(yield: 98%).
16
17
92
90
4.6. Analytical data
N-Phenylbenzamide17 1a. White solid; mp 163–164 1C; yield:
75%; molecular formula:C13H11NO; 1H NMR (300 MHz,
CDCl3) d 7.13–7.86 (m, 10H); 13C NMR (75 MHz, CDCl3)
d 165.73, 146.30, 137.88, 134.96, 131.82, 129.24, 129.07,
128.76, 126.98, 124.55, 120.17, 118.53, 115.08. Commercial
compound
were characterized using a BET surface area analyzer BELSORP.
Thermal behavior of the prepared nanostructured materials
was examined on a Perkin-Elmer (Wellesley, MA) instrument
under a nitrogen atmosphere at a heating rate of 20 1C minÀ1
from 30 to 800 1C. 1H NMR and 13C NMR spectra were
recorded in CDCl3 on a Bruker Avance 300 MHz spectro-
meter and the chemical shifts are reported as d values in parts
per million (ppm) relative to tetramethylsilane, with J values in
Hertz. The splitting patterns in the 1H NMR spectra are
reported as follows: s = singlet; d = doublet; t = triplet;
q = quartet; m = multiplet. 13C NMR data are reported with
the solvent peak (CDCl3 = 77.0) as the internal standard. The
spectral data of all known compounds are consistent with
those reported previously.
N,2-Diphenylacetamide18 1b. White solid; mp 118–119 1C;
yield: 98%; molecular formula: C14H13NO; 1H NMR (300 MHz,
CDCl3) d 6.67–7.42 (m, 10H), 3.72 (s, 2H); 13C NMR
(75 MHz, CDCl3) d 169.14, 137.60, 134.40, 129.50, 129.52,
129.19, 128.91, 127.63, 124.44, 119.83, 118.52, 115.07, 44.77.
N-(4-Methoxyphenyl)benzamide19 1c. White solid; mp
147–157 1C; yield: 75%; molecular formula: C14H13NO2;
1H NMR (300 MHz, CDCl3) d 8.22–6.67 (m, 10H), 3.87
(s, 2H); 13C NMR (75 MHz, CDCl3) d 165.19, 138.224,
129.08, 128.90, 124.377, 120.22, 114.08, 55.48.
2-Phenoxy-N-phenylacetamide20 1d. White solid; mp 99–100 1C;
yield: 93%; molecular formula: C14H13NO2; 1H NMR (300 MHz,
CDCl3) d 8.33 (bs, 1H), 7.622–6.98 (m, 10H), 6.60 (s, 2H); 13
C
4.2. Synthesis of titania nanoparticles
NMR (75 MHz, CDCl3) d 166.25, 157.12, 136.93, 129.89,
129.05, 124.83, 122.47, 120.17, 114.93, 67.77.
Ti(IV)-iso propoxide solution was injected in to the 5 M HCl
aqueous solution and magnetically stirred for 1 h. Then the
prepared nanoparticles were centrifuged and were annealed at
400, 600 and 800 1C for the phase determination/transformation
studies.
N-Phenylfuran-2-carboxamide21 1e. White solid; mp
131–132 1C; Yield: 85%; Molecular Formula: C11H9NO2;
1H NMR (300 MHz, CDCl3) d 8.08 (bs, 1H), 7.67–6.55
(m, 8H); 13C NMR (75 MHz, CDCl3) d 155.96, 147.89,
144.04, 137.36, 129.03, 124.45, 119.88, 115.13, 112.52.
4.3. Synthesis of titania nanotubes
A stipulated amount of freshly prepared titania nanoparticles
was suspended in 20 mL of 10 M sodium hydroxide aqueous
solution. The resulting suspension was taken in a teflon vessel
and placed in an autoclave at 150 1C for 20 h. Then the samples
were washed with 0.1 N HCl aqueous solution, deionized
water, and were subsequently separated via the centrifugation
N-(4-Nitrophenyl)benzamide8 1f. White solid; mp 162–164 1C;
yield: 77%; pale yellow solid; mp = 199 1C; molecular
1
formula: C13H10N2O3; H NMR (300 MHz, CDCl3) d 10.31
(bs, 1H), 8.34–7.125 (m, 10H); 13C NMR (75 MHz, CDCl3)
d 163.12, 158.32, 14.03, 137.29, 127.88, 127.30, 123.03, 121.96,
119.66.
c
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N-Phenylcinnamamide22 1g. White solid; mp 1501–152 1C;
yield: 87%; molecular formula: C15H13NO; 1H NMR
(300 MHz, CDCl3) d 8.46 (bs, 1H), 7.75 (d, J = 15.9 Hz,
1H); 7.69–7.09 (m, 10H), 6.71 (d, J = 15.6 Hz, 1H); 13C NMR
(75 MHz, CDCl3) d 163.12, 158.32, 14.03, 137.29, 127.88,
127.30, 123.03, 121.96, 119.66.
13C NMR (75 MHz, CDCl3) d 165.67, 138.94, 137.88, 135.13,
131.66, 128.82, 128.68, 126.96, 125.33, 120.92, 117.34, 21.38.
2-Phenoxy-N-m-tolylacetamide 3c. White solid; mp 93–94 1C;
yield: 90%; molecular formula: C15H15NO2; 1H NMR
(300 MHz, CDCl3) d 8.25 (bs, 1H), 7.42–6.95 (m, 9H), 4.59
(s, 2H), 2.35 (s, 3H); 13C NMR (75 MHz, CDCl3) d 166.15,
157.02, 138.99, 136.73, 129.85, 128.85, 125.63, 122.40, 120.70,
117.18, 114.83, 67.64, 21.39.
N-(4-Chlorophenyl)benzamide23 1h. White solid; mp 199–200 1C;
yield: 81%; molecular formula: C13H10ClNO; 1H NMR
(300 MHz, CDCl3)
d
8.12–7.16 (m, 10H); 13C NMR
(75 MHz, CDCl3) d 164.60, 140.21, 138.13, 137.64, 133.35,
131.52, 129.09, 129.01, 128.81, 128.40, 124.77, 120.28.
Acknowledgements
The authors thank IRHPA, DST for providing the 300 MHz
NMR instrument for recording the NMR spectra and S. N.
and P. S. acknowledge their grateful thanks to UGC for the
sanction of UGC(BSR)–JRF meritorious fellowship. P. R.
and K. S. were supported by the Human Resources Develop-
ment of the Korea Institute of Energy Technology Evaluation
and Planning (Ketep) grant funded by the Korean government
Ministry of Knowledge Economy.
N-Phenylpropionamide24 1i. White solid; mp 105–106 1C;
yield: 92%; molecular formula: C9H11NO; 1H NMR (300 MHz,
CDCl3) d 8.39 (bs, 1H), 7.56–7.05 (m, 5H), 2.37 (q, J =
7.5 Hz, 2H), 1.20 (t, J = 7.5 Hz, 3H); 13C NMR (75 MHz,
CDCl3) d 129.18, 128.74, 124.30, 120.18, 115.08.
N-Phenylbutyramide25 1j. White solid; mp 82–84 1C; yield:
94%; molecular formula: C10H13NO; 1H NMR (300 MHz,
CDCl3) d 8.51 (bs, 1H), 7.57–6.66 (m, 5H), 2.31 (t, J = 7.5 Hz,
2H), 1.71 (sextet, J = 7.5 Hz, 2H), 0.95 (t, J = 7.5 Hz, 3H);
13C NMR (75 MHz, CDCl3) d 172.12, 138.02, 129.02, 123.89,
120.10, 118.28, 114.96, 39.12, 18.93, 13.45.
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c
1318 New J. Chem., 2012, 36, 1312–1319
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