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ULTRASONIC VELOCITY STUDIES OF BENZOIC ACID AND SUBSTITUTED BENZOIC ACIDS IN AQUEOUS MIXED SOLVENT SYSTEMS

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Vol. 14 | No. 4 |2622-2626| October- December | 2021
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Rasayan J. Chem., 14(4), 2622-2626(2021)
http://dx.doi.org/10.31788/RJC.2021.1445767
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ULTRASONIC VELOCITY STUDIES OF BENZOIC ACID AND
SUBSTITUTED BENZOIC ACIDS IN AQUEOUS MIXED
SOLVENT SYSTEMS
S. Jagan Raj1,, V. Subha2 and S. Bangaru Sudarsan Alwar3
1Department of Chemistry, Velammal Institute of Technology, Panchetti, Chennai
2Department of Chemistry, R.M.D Engineering College, Kavaraipettai, Chennai
3Department of Chemistry, D.G. Vaishnav College, Arumbakkam, Chennai
Corresponding Author: sjaganraj27@gmail.com
ABSTRACT
The ultrasonic velocity of benzoic acid and substituted benzoic acids such as para chloro benzoic acid, para nitro
benzoic acid and meta nitro benzoic acid in ethanol-water binary solvent mixtures of several compositions were
evaluated. It finds immense applications in the field of several technological and industrial processes such as
petrochemical, pharmaceutical and in the manufacture of dyes. The results of ultrasonic velocity determination are
remarkably important in the determination of liquid mixtures that are made up of polar and non-polar compounds.
The structural modifications of ethanol get into a 3-D network of linkages made up of hydrogen bonds in liquid
mixtures. In the present study, it is inferred that a weak molecular association exists between ethanol and the
substituted benzoic acids through weak dipole-dipole interactions. The probability of the development of donor-
acceptor complexes has also been examined and subsequently discussed. In addition, the effect of substituents like
the nitro and the chloro group at the para and meta positions has also been interpreted.
Keywords: Benzoic Acid, Ultrasonic Velocity, Solute-solvent Interactions
RASĀYAN J. Chem., Vol. 14, No.4, 2021
INTRODUCTION
The results of ultrasonic velocity studies are extremely useful in identifying the acoustical and
thermodynamic parameters that are significantly perceptive to molecular interaction studies.1,2 The structure
of molecular liquids can be speculated from the results of thermodynamic and transport properties. The
results also throw light on the presence of intermolecular interactions that exist in the liquid mixtures.
Alcohols are highly self-associated liquids. Both inter and intramolecular hydrogen bonding is found in
alcohols.
The most important property of alcohols is their application as solvents and they are of a major utility in
biology, chemistry and pharmaceutical studies. Likewise substituted benzoic acids like p-chloro benzoic
acid, m-nitrobenzoic acid and p-nitrobenzoic acid are mainly used in a variety of industrial applications.
The 3-D network of hydrogen bonding in alcohols makes it an interesting aspect to highlight the diverse
types of molecular interactions and associations in organic ternary mixtures having alcohol, a self-
associated liquid in the mixtures. It can associate with any other compound which has a group that is
susceptive to polar associations.
The variation of ultrasonic velocity unravels the changes associated with the structure of the weakly
associating and strongly associating components in the binary liquid mixtures.3-5 The molecules of benzoic
acid are connected by hydrogen bonds and exist as a dimer with D2h symmetry. There are several chances
for ethanol to interlink and form a complex which is hydrogen-bonded with benzoic acid and the substituted
benzoic acids. The structure may be due to the nature of ethanol which can act both accept hydrogen bonds
strongly as well as act as a weak hydrogen bond donor.
Thus, mixing the different substituted benzoic acids in aqueous ethanol mixtures gives interesting results
due to the presence of specific interactions that may arise due to the charge-transfer forces, dipole-dipole
interactions, donor-acceptor properties and hydrogen bonding of the mixtures.
Vol. 14 | No. 4 |2622-2626| October- December | 2021
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ULTRASONIC VELOCITY STUDIES OF BENZOIC ACIDS S. Jagan Raj et al.
EXPERIMENTAL
Analytical grade and highly pure chemicals purchased from E. Merck, India were used in this study.
Standard procedures were used to purify and redistill the solvent.7-9 A single crystal variable path
interferometer of an accuracy ± 0.05 % was used to calculate the ultrasonic velocity of liquid mixtures.
Triply distilled water (with a specific conductivity of 1x 10-7 S cm-1) was used throughout this study.
RESULTS AND DISCUSSION
In this section, the measured results of ultrasonic sound velocity of benzoic acid, p-chloro benzoic acid, m-
nitrobenzoic acid and p-nitrobenzoic acid in aqueous ethanolic mixtures at 303.18 K are interpreted. These
values are given in Tables -l and 2.
Table1: Experimental Data of Ultrasonic Velocity of C6H5COOH in Ethanol-water Mixtures (v/v)
[Benzoic Acid]
(M)
Experimental Data of Ultrasonic Velocity of C6H5COOH in Ethanol-water Mixtures (v/v)
U
) ( 1
sm
5%
10%
15%
20%
25%
50%
60%
80%
6.25E
-
05
1534.7
1542.1
1553.3
1550.3
1566.1
1572.7
1531.7
1399.7
1.25E
-
04
1536
1548.9
1555.1
1567.3
1570.7
1587.2
1545.9
1413.9
2.50E
-
04
1548.1
1554
1557.4
1574.7
1594.5
1598.5
1561.3
1426.3
5.00E
-
04
1550.1
1564.9
1560.8
1585.5
1597.5
1630.3
1578.6
1438.6
1.00E
-
03
1552
1573.1
1562.9
1600.4
1603.7
1674.5
1594.1
1439.1
Table-2: Experimental Data of Ultrasonic Velocity of Substituted Benzoic Acids in Aqueous Ethanol-water
Mixtures (v/v)
[Concentration]of
the substituted
Benzoic Acid
(M)
The Ultrasonic Velocity of Substituted Benzoic Acids in Aqueous Ethanol-water Mixtures
(v/v)
U
) ( 1
sm
20%
50%
80%
p-CBA p-NBA m-
NBA
p-CBA p-NBA m-
NBA
p-CBA p-NBA m-
NBA
0.0001
1604
1616
1614
1552
1485
1600
1490
1395
1579
0.00005
1550
1523
1602
1510
1450
1590
1461
1351
1512
0.000025
1520
1470
1596
1482
1430
1578
1445
1325
1490
0.0000125
1504
1445
1585
1470
1425
1563
1440
1315
1480
Table-1 interprets the results of ultrasonic velocity measurements of benzoic acid in aqueous ethanol
mixtures. Figure-1 illustrates the outcomes of ultrasonic velocity measurements of benzoic acid in aqueous
ethanol mixtures. Table-2 infers the results of ultrasonic velocity measurements of the substituted benzoic
acids in aqueous ethanol mixtures. Figures-2, 3 and 4 represent the variation of ultrasonic velocity with a
concentration of the substituted benzoic acids in different volume fractions of ethanol and water
respectively. It is observed that with a raise in the molar concentration of the solute, there is a trivial increase
in the ultrasonic velocity. The increase in ultrasonic velocity was observed for benzoic acid and substituted
benzoic acids until 50%, which then decreases. The difference in ultrasonic velocity can be directly related
to the changes in the intermolecular free length. The same trend in results is also reported earlier by several
researchers.3-6 The ultrasonic velocities of the acids decrease at all concentrations at 80% volume fractions
of ethanol-water media.
Literature reports from X-ray diffraction, mass spectroscopic and spectroscopic analysis10-12 highlight the
results of ethanol-water mixtures. It is expected that the solvation behavior is primarily due to the solute-
solvent interactions. However, literature reports10 underline that the solvation behavior of ethanol-water
mixtures is due to the clustering structure of the mixed solvent system. The bulk water structure completely
breaks down at higher ethanol compositions.11 It is also known that at a selected mole fraction of ethanol
(XE>0.15), a huge set of hydrogen bonds are produced between the water and ethanol molecules. This can
also be portrayed by a cluster model which can be visualized as a piled ethanol core encircled by a thin
water shell.10-12
Vol. 14 | No. 4 |2622-2626| October- December | 2021
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ULTRASONIC VELOCITY STUDIES OF BENZOIC ACIDS S. Jagan Raj et al.
Fig.-1: Ultrasonic Velocity measurements for the Variation of Ultrasonic Velocity of C6H5COOH in Ethanol-water
Media (v/v)
The addition of benzoic acid to water molecules initially disturbs the structure of water which eventually
leads to certain structural changes in the solution that produce closely fitting helical cavities13. In lower
proportions of ethanol, benzoic acid and the substituted benzoic acids dissociate into their corresponding
ions in the solution. The ultrasonic velocity initially increases which is due to the strong electrostatic
interactions amongst the benzoate ions and water molecules. The structural changes may be in agreement
with the tendency of ethanol which can both accept hydrogen bonds, as well as donate hydrogen bonds.
Thus as reported earlier, increased ionic hydration and cohesion in the medium is hence expected.
Fig.-2: Ultrasonic Velocity measurements for substituted Benzoic Acids in 20% Volume Fractions of Ethanol
As the concentration of the solution increases, all the three substituted benzoic acids such as p-CBA, p-
NBA and m-NBA show an increase in ultrasonic velocity. It is seen from Figures-2, 3 and 4 that p-NBA
showed the greatest increase in velocity. At 50% fraction of ethanol-water media, m-NBA displayed higher
velocity values than p-CBA and p-NBA (Fig.-3). However, m-NBA reveals higher velocity at 80% volume
fractions of ethanol in the solution (Fig.-4). The highest velocity is observed in m-NBA relative to p-NBA
and p-CBA. The results denote the presence of strong intermolecular interactions between m-NBA and
ethanol-water molecules in comparison to p-NBA and p-CBA. It is also inferred that for all the three
substituted benzoic acids the solute-solvent interactions predominates at fractions of ethanol less than 50%
and solvent-solvent interactions predominate after 50% of ethanol. This is attributed to the breaking down
of the structure of water at such greater compositions.14 As the substituted benzoic acids dissolve in greater
1300
1400
1500
1600
1700
0.00E+00 2.00E-04 4.00E-04 6.00E-04 8.00E-04 1.00E-03 1.20E-03
Ultrasonic velocity U (m s-1)
Concentration of Benzoic acid (M)
5% ethanol 10% ethanol 15% ethanol 20% ethanol
50% ethanol 60% ethanol 80% ethanol
1400
1450
1500
1550
1600
1650
0 0.00002 0.00004 0.00006 0.00008 0.0001 0.00012
Ultrasonic velocity U (m s-1)
Concentration (M)
p-CBA p-NBA m-NBA
Vol. 14 | No. 4 |2622-2626| October- December | 2021
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ULTRASONIC VELOCITY STUDIES OF BENZOIC ACIDS S. Jagan Raj et al.
proportions of ethanol to form a miscible solution at any proportion, there is an association of the
intermolecular attractive forces, as like dissolves like. The results of ultrasonic velocity probe into the extent
of molecular interactions existing in the system due to solvation which may be of tremendous use in a
number of industrial processes like the petrochemical and the pharmaceutical industry.
Fig.-3: Ultrasonic Velocity measurements for substituted Benzoic Acids in 50% Volume fractions of Ethanol
Fig.-4: Ultrasonic Velocity measurements for substituted Benzoic Acids 80% Volume fractions of Ethanol
CONCLUSION
Owing to these physical parameters of substituted benzoic acids, alcohol and water, the present study of
molecular interaction studies of substituted benzoic acids in the binary solvent mixtures of ethanol and
water has been carried out. Although extensive work has been carried out about the reactivity of several
compounds in binary solvent mixtures, the study of substituted benzoic acids in such mixtures is really rare.
The collective effect of alcohol and water as binary solvents in which substituted benzoic acids were added
as solutes at various mole fractions has been an unusual study and almost no systematic reports were carried
out earlier. The acoustical properties of liquid binary mixtures were extensively carried out to examine the
variation of the binary mixtures from ideality. The structure, nature and geometry of both the solvent and
solute molecules decide the amount of molecular interactions present in a system. The acoustical properties
of systems containing ethanol-water mixtures with both benzoic acid and substituted benzoic acids throw
light on the impact of molecular interaction on the structure of the compounds in the liquid mixtures.
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1400
1450
1500
1550
1600
1650
0 0.00002 0.00004 0.00006 0.00008 0.0001 0.00012
Ultrasonic velocity U (m s-1)
Concentration (M)
p-CBA p-NBA m-NBA
1300
1350
1400
1450
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0 0.00002 0.00004 0.00006 0.00008 0.0001 0.00012
Ultrasonic velocity U (m s-1)
Concentration (M)
p-CBA p-NBA m-NBA
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  • R K Dewan
  • S K Mehta
  • J Singh
R.K. Dewan, S.K. Mehta and J. Singh, Acta Acustica United with Acustica, 74(4),284(1991).
  • G Arul
  • L Palaniappan
G.Arul. and L. Palaniappan, Journal of the Acoustical Society of India, 28, 393(2000).
  • D Bala Karuna
  • K Kumar
  • G Reddy
  • G V Rao
  • C Rama Rao
  • Rambabu
D. Bala Karuna Kumar, K. Rayapa Reddy, G. Srinivasa Rao, G.V. Rama Rao and C. Rambabu, Asian Journal of Chemistry, 24(5), 2239(2012).
  • S Raj
  • V Subha
  • Bangaru Sudarsan Alwar
S.Jagan Raj, V.Subha and Bangaru Sudarsan Alwar, Journal of Chemical, Biological and Physical Science, 2(4), 650(2017)
  • B Reddy
  • Y Haribabu
  • D Linga Reddy
B. Ravinder Reddy, Y. HariBabu, D. Linga Reddy, Indian Journal of Pure and Applied Physics, 37, 13(1999).