Journal of Minerals & Materials Characterization & Engineering, Vol. 9, No.5, pp.471-481, 2010
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471
Growth and Characterization of Urea Adduct with m-Nitrobenzoic Acid,
m-Nitroaniline, and p-Xylene Mixtures
P. Jagdish1*, N.P. Rajesh2, S. Natarajan3
1Department of Physics, Sona College of Technology, Salem – 636 005, India
2Centre for Crystal Growth, SSN College of Engineering, Kalavakkam – 636 110, India.
3School of Physics, Madurai Kamaraj University, Madurai – 625 021, India.
*Corresponding author: [e-mail], [e-mail]
ABSTRACT
The urea adduct with the guests of m-nitrobenzoic acid, m-nitroaniline and p-xylene mixtures by
adductive crystallization was successfully grown by slow evaporation method. The single
crystals obtained were non-hygroscopic and good in size. The crystal structure of the grown
crystal has been determined, and it belongs to the monoclinic system with centrosymmertic space
group P21/c. Fourier transform infrared spectroscopic studies were performed for the
identification of guest components in the compound. The optical absorption spectrum has been
recorded in the range 200-1100 nm. The mechanical behavior of the specimen was studied.
Key words: X-ray diffraction, Growth from solutions, Organic adduct.
1. INTRODUCTION
The development of new optical organic materials is of great interest due to their higher orders of
optical transparencies than the conventional inorganic materials. Due to promising optical
properties, the organic materials can be utilized in optical device fabrication which can replace
the electronic switching circuits [1]. So it is required to grow highly perfect single crystals of
organic optical materials for optical devices fabrication with unique properties such as good
transparency, large birefringence and frequency mixing in the large range of spectrum including
the ultraviolet spectrum [2-6]. In this work, a new organic adduct has been formed with urea, m-
nitrobenzoic acid, m-nitroaniline and p-xylene mixtures and was grown as a single crystal. In the
present investigation, we report the synthesis, crystal growth, single-crystal X-ray diffraction

472 P. Jagdish, N.P. Rajesh, S. Natarajan Vol.9, No.5
(XRD) studies, Fourier transform infrared (FT-IR) spectroscopy, optical transmission (UV-vis-
NIR), Vicker’s micro hardness test of the new organic adduct.
2. EXPERIMENTAL
2.1 Synthesis
The organic adduct was synthesized by the combination of urea (Merck, 99.5% pure), m-
nitrobenzoic acid (Merck, 99.5% pure), m-nitroaniline (Merck, 99.5% pure) and p-xylene (AR
grade) along with methanol (AR grade) as solvent. Homogeneous solutions were prepared by
dissolving 17.48 g, 13.812 g and 16.7 g of urea, m-nitrobenzoic acid and m-nitroaniline,
respectively, in methanol of 100 ml each. The three solutions thus formed were thoroughly
mixed by constant stirring along with p-xylene (100ml) in the ratio 1:1:1:1 and heated to a
temperature of 40°C. The solution was then filtered out and kept undisturbed at a temperature of
40°C in a closed beaker with provision for controlled evaporation. After a period of one week,
crystalline material of urea adducts with organic mixture was separated out and dried using a
vacuum oven. The purity of the synthesized salt was further improved by successive
recrystallization of the compound in methanol.
2.2 Crystal Growth
Single crystals of urea adduct with m-nitrobenzoic acid, m-nitroaniline and p-xylene mixture
were grown by solvent evaporation technique at room temperature. Appropriate selection of
solvent for the growth of the material is very important in crystal growth process. Methanol was
found to be the suitable solvent for preparing the growth solutions. Recrystallized compound was
dissolved in methanol to prepare a saturated solution. The solution was filtered and kept
undisturbed in a dust free environment at room temperature. The rate of evaporation of the
solvent was controlled critically for a period of thirty days. Finally the single crystals of urea
adduct with m-nitrobenzoic acid, m-nitroaniline and p-xylene mixture were harvested. Figure 1
shows the photograph of the harvested single crystal exhibiting birefringence property.

Vol.9, No.5 Growth and Characterization of Urea Adduct 473
Figure 1. Photograph of urea adduct with m-nitrobenzoic acid-m-nitroaniline-p-xylene
mixture single crystal (C8H9N3O5).
3. RESULTS AND DISCUSSIONS
3.1 X-ray Diffraction Analysis
To obtain the unit cell parameters and to confirm the crystallinity of grown crystals, both single
crystal and powder crystal X-ray diffraction studies were carried out. Single crystal X-ray
diffraction pattern was recorded using single crystal diffractometer CAD 4/MACH 3 with MoKα
radiation in the wavelength 0.71073 Ǻ. The cell parameters were calculated by data reduction
and the structure was solved. The unit cell parameters were measured at 293 K. The unit cell
dimensions were determined as a = 8.093 (5) Å, b = 12.750 (5) Å, c = 9.502 (5) Å, α =90.00°, β
= 93.39 (5)°, γ = 90.00° and the cell volume of 978.8 (9) Å3 with a molecular weight of 227.18 g.
The crystal belongs to monoclinic crystal system with space group of P21/c. The crystal data,
experimental conditions and structural refinement parameters of urea adduct with m-nitrobenzoic
acid-m-nitroaniline-p-xylene mixture single crystal are presented in Table 1.
Figure 2 shows the planar molecular structure of the adduct that has been determined by single
crystal XRD. The molecular packing diagram given in Figure 3 shows four molecules per unit
cell. The calculated cell parameters were also searched through Cambridge Structural Database
which revealed that the crystal grown is a new organic adduct.

474 P. Jagdish, N.P. Rajesh, S. Natarajan Vol.9, No.5
Table 1. Crystal data and structure refinement for urea adducts with m-nitrobenzoic acid-m-
nitroaniline-p-xylene mixture single crystal (C8H9N3O5).
Empirical formula C8H9N3O5
Formula weight 227.18
Temperature 293(2) K
Wavelength 0.71069 Ǻ
Crystal system Monoclinic
Space group P21/c
Unit cell dimensions
a = 8.093(5) Ǻ, α = 90.00°
b =12.750(5) Ǻ, β = 93.39(5)°
c = 9.502(5) Ǻ, γ = 90.00°
Volume 978.8(9) Ǻ3
Z, Calculated density 4, 1.542 gm/cc
Absorption coefficient 0.130 mm-1
F (000) 472
Crystal size 0.29 x 0.26 x 0.21 mm3
Theta range for data collection 2.52 to 24.98°
Limiting indices 0≤h≤9, -1≤k≤15, -11≤l≤11
Reflections collected / unique 2024 / 1717 [R(int) = 0.1344]
Completeness to theta 24.98, 99.6%
Absorption correction φ scan
Refinement method Full-matrix least-squares on F2
Data/restraints/parameters 1717/0/146
Goodness-of-fit on F2 1.069
Final R indices [I>2sigma(I)] R1 = 0.1000, wR2 = 0.2676
R indices (all data) R1 = 0.1703, wR2 = 0.3216
Extinction coefficient 0.016(9)
Largest diff. peak and hole 0.515 and -0.397 e.Ǻ3

Vol.9, No.5 Growth and Characterization of Urea Adduct 475
Figure 2. The molecular diagram of C8H9N3O5 with numbering scheme.
Figure 3. Molecular packing diagram of C8H9N3O5 viewed down to the c-axis.
Powder X-ray diffraction study was carried out and the peaks were recorded using a
microprocessor controlled X-ray diffractometer with 1.5405 Cu wavelength as the target in
reflection scan mode using scintillation counter detector. The grown crystals were finely
powdered and employed for powder XRD. The sample was scanned over the range 10-70o at the
rate of 1o/min. From the X-ray diffraction data the various planes of reflections were indexed
and the indexed powder X-ray diffraction pattern is given in Figure 4.

476 P. Jagdish, N.P. Rajesh, S. Natarajan Vol.9, No.5
Figure 4. Powder XRD of urea adducts with m-nitrobenzoic acid-m-nitroaniline-
p-xylene mixture single crystal.
3.2 FTIR Analysis
The FTIR spectrum was recorded using a Perkin-Elmer FTIR spectrum RXI spectrometer by
KBr pellet technique. Figure 5 shows the FTIR spectrum recorded in the range 400-4000 cm-1 at
room temperature. The assignment of FTIR data of the crystal is given in Table 2, which shows
the evidence of presence of different functional groups of the reactants.
The adduct formation is due to very high intermolecular hydrogen bonding forces that was
existing between urea and the carbonyl group of m-nitrobenzoic acid supported by m-
nitroaniline. Hence they were pulled towards each other to form a very strong adduct. The adduct
formation is greatly influenced by the presence of methanol [7] and p-xylene [8] as solvents.

Vol.9, No.5 Growth and Characterization of Urea Adduct 477
Table 2. Assignment of FTIR data of urea adducts with m-nitrobenzoic acid - m-nitroaniline –p-
xylene mixture single crystal.
Wavenumber (cm-1) Tentative Assignment
3771.17 O-H stretching, C-H stretching – weak to medium
3486.89 O–H stretch(attached to benzene ring), broad very intense, strong
2930.15 C─H Methylene – weak to medium
2859.75 C─H Alkyl methyl – weak to medium
2790.17 C─H Aldehyde – medium
2600.08 C ≡ N (attached to benzene ring) , C ≡ C weak to medium
2425.06 N─H(ammonium ions) multiple broad peaks
1930.67 C═C, C═O broad peak
1630.57 Ester Carbonyl stretch; typically sharp and intense, strong band
consistent with C=C, NH bend-amide II – medium
1521.53 Double bond stretch, N─O (aromatic) sharp-medium to strong
1472.54 C═C stretch, C─H(alkyl) methylene- medium to strong
1351.06 N─O(aromatic), C–H deformation
1269.41 C─O (ethers) aromatic, carboxylic acids
1143.51 C–O stretch; typically broad and intense
1068.77 C─O (primary alcohol) strong - broad, C─N (aliphatic amine) often
overlapped
890.43 C─H (aromatic) meta-bisubstituted benzene
779.10 C─H (aromatic) meta-bisubstituted benzene
711.13 C─H (aromatic) mono substituted benzene – strong
3.3 Optical Transmission Studies
The UV-vis-NIR study of the single crystal was done using Lambda 35 UV spectrophotometer.
Figure 6 shows the optical absorption spectrum of urea adduct single crystals grown from
methanol. The crystal shows good optical transmittance in the entire region; therefore this new
organic adduct material is best suited for electro-optic modulation [9]. It shows a cutoff at 264.37
nm. This reveals that, in the grown crystal the absorption is almost absent in the visible region
due to its high transparency.

478 P. Jagdish, N.P. Rajesh, S. Natarajan Vol.9, No.5
Figure 5. FTIR spectrum of urea adducts with m-nitrobenzoic acid-m-nitroaniline-
p-xylene mixture single crystals.
Figure 6. UV-Vis-NIR absorption spectrum of urea adducts with m-nitrobenzoic acid-m-
nitroaniline-p-xylene mixture single crystals.

Vol.9, No.5 Growth and Characterization of Urea Adduct 479
3.4 Microhardness Studies
Vicker’s microhardness number was used to evaluate the anisotropy in mechanical hardness for
the single crystals of thickness 3 mm employing a Shimadzu HMV-2 microhardness tester for
different loads. The selected smooth surfaces of the crystal were subjected to Vicker’s static
indentation test at room temperature by applying loads ranging from 25-200 g. The Vickers
hardness HV was calculated using the relation HV = 1.8544 (P/d2) kg/mm2, where P is the applied
load and d is the diagonal length of the indentation impression.
The microhardness value was taken as the average of the several impressions made. Crack
initiation and materials chipping become significant beyond 200 g of the applied load. Figure 7
shows the variation of microhardness number (HV) as a function of applied load (P).
It is clear from the figure that the microhardness number decreases with increase of load. The
Mayer's number (n) is found to be 1.84, which concludes that the crystal belongs to the soft
category.
Figure 7. Variation of Microhardness number (HV) with load (P).

480 P. Jagdish, N.P. Rajesh, S. Natarajan Vol.9, No.5
4. CONCLUSIONS
The urea adduct with m-nitrobenzoic acid, m-nitroaniline and p-xylene mixture was synthesized
and grown as single crystal by slow evaporation solution growth technique at room temperature.
The grown crystals are nonhygroscopic and have well developed habit. The single crystal X-ray
diffraction study confirmed its crystal structure belonging to monoclinic crystal system with
centrosymmetric space group P21/c. The molecular packing shows four molecules per unit cell.
The FTIR spectrum shows the incorporation of different functional of the guest reactants. The
adduct formation of urea with its guests in a very strong manner is highly influenced by p-xylene
and methanol. The strong forces provided by the secondary bonding between the amide and
carboxyl group has favored the electron transfer between them. The excellent transparency in the
entire UV-vis-NIR region facilitates this material to various optical applications. The
microhardness studies concludes the category of the organic adduct crystal as soft category.
ACKNOWLEDGEMENT
This work, supported by the Department of Science and Technology, New Delhi, India under the
grant of project ref- SR/FTP/PS-20/2005, is hereby gratefully acknowledged. One of the authors
(P. Jagdish) thanks Sona College of Technology, Salem, India for their help and encouragement
to carry out this research work.
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