INTRODUCTION:
Aromatic aldehydes (AAs) are used as precursor in many industries such as pharmaceuticals, fragrances, chemicals, dyes, flavours1 and synthesis of flavanone2. These are also toxic environmental pollutants3. The manufacturing of products having aromatic aldehyde is finite due to its toxicity. In addition, salicylaldehyde (SA) is used in numerous industrial, pharmaceutical, biological applications4 and for the preparation of schiff base complexes5,6. Also, it is naturally found in tomato, cinnamon, grape, coffee, tea and milk products. Due to widespread uses of salicyaldehyde, it becomes an organic pollutant and finds its path into aqueous system by pharmaceutical and industrial fields7. To determined SA many methods are developed such as differential pulse polarographic8 colorimetric9 cyclic and normal pulse voltammetry10 spectroelectrochemistry7, electrochemical11, uv/spectroscopy12 and also salicylaldehyde is determined in natural and treated water by applying GC-MS13. Continuous increase of pollutants in water bodies14,15 have necessitated the development of cost-effective methods for their removal or degradation.
Electrochemical analysis is a powerful analytical technique used in pharmaceutical industry, metal industry and environmental applications16 due to its high sensitivity, good stability, rapid response, low operating cost, and accuracy17,18,19. Currently voltammetry is an eco-friendly technique to investigate pollutants and other compounds20. It is widely used for determination and kinetic mechanism of the reaction21. In this work, we reported electro-oxidation of salicylaldehyde in non aqueous solvent acetonitrile using cyclic voltammetry technique. To our best knowledge salicylaldehyde have not yet been investigated in non-aqueous solvent using these parameters.
MATERIAL AND METHODS:
Chemicals and reagents:
All the chemical such as salicylaldehyde (Merck), acetonitrile (sigma Aldrich) and HClO4 were of analytical grade and used to carried out the experiment. Acetonitrile was used as solvent and HClO4 served as supporting electrolyte. All experiments were carried out at room temperature (250C -260C).
Instrumentation:
An Autolab model PGSTAT 101 potentiostat/ galvanostat 663 VA Stand (Metrohm AG, Netherlands) was used to perform CyclicVoltammetry (CV) technique. In this technique electrochemical cell consisting three electrode system. Pt disc electrode (PE) (0.031cm2) acted as working electrode (WE), Ag/AgCl/3M KCl electrode as the reference electrode and a Pt wire acted as the counter electrode. Prior to investigation, working electrode was polished with alumina powder (particle size 0.05mm) on a cloth polishing pad and washed with dry acetone.
RESULTS AND DISCUSSION:
In the present work, the cyclic voltammetry technique was used to study the electro oxidation of SA, to find out the kinetic and electrochemical parameters.
Cyclic Voltammetry Experiment of Salicylaldehyde (SA) on Platinum Electrode(PE):
The electrochemical behaviour of SA was recorded on platinum electrode in the potential window range from +1.0 V to +2.6 V at the 20mVs-1 to 180mVs-1 different scan rate in a voltammetric cell with the SA solution (1.5×10 -2 M) in acetonitrile in presence of HClO4 as a supporting electrolyte. Kinetic parameters were determined by the peak current (Ip) under the influence of scan rate (v). CV of salicylaldehyde showed only one anodic peak at the v =20 mVs-1[Figure 1].This peak indicates that the irreversible reaction was occurred on the platinum electrode surface. On scanning the reverse direction there was no cathodic peak showed.
Figure 1: Cyclic Voltammogram of 1.5× 10-2 M Salicylaldehyde (v =20mVs-1,supporting electrolyte 0.1M HClO4)
Influence of scan rate:
The influence of different scan rate on SA was analyzed by using cyclic voltammetry technique [figure 2].The peak current(Ip) and peak potentials(Ep) were determined for the first scan of SA electro- oxidation at different scan rate.
Figure 2: Cyclic voltammograms of 1.5 × 10-2 M SA at different scan rate 20,40,60,80,100,120,140,160, and 180 mVs-1
For electrochemical reaction rate, the reversibility controls by adsorption and diffusion and it depends on two factors: Ip on v1/2 and log Ip on log v22 [Figure 3(a),(b)].If origin of the coordinates is not intercepted by the linear fit [figure. 3(a)],the electrode process is diffusion control and proceeded by chemical reaction23. At various scan rate (v) ranging from 0.02 to 0.18Vs-1, peak current(Ip) depends linearly on the square root of v (equation below):
Ip(µA)= 550.07 v1/2 (V1/2 s - 1/2) ‒ 21.912 (r=0.995)
Figure 3(a): Ipa vs v1/2
Alternatively, linear relationship was observed between log Ip and log v [figure 3(b)] corresponding to the equation.
log Ip (µA)=0.577 log v (Vs-1)+2.755 (r=0.993)
Figure 3(b): log Ip vs log v
The slope value of this linear fit [figure3(b)] is 0.57. Therefore according to Bard, Faulkner and others24, this process is only controlled by diffusion.which confirms that the electro-oxidation of SA was diffusion controlled reaction.With an increase in scan rate,the peak potential was observed in the range 0.02-0.18Vs-1.as shown in [figure3(c)] .The relationship can be expressed as:
Ep (V) = 0.15 log v (Vs-1)+ 2.241 (r=0.998)
Figure 3(c):Ep vs log v
For irreversible electrode process, Laviron25 equation is given below to define Ep:
Ep= E0 + (2.303RT/αnF) log (RTk0/αnF) + (2.303RT/αnF) log v
Where
E0 is the formal standard redox potential, α is the transfer
coefficent, n is the number of electron transferred, k0 is the
standard heterogeneous rate constant of the reaction, v is the scan
rate.Thus from the slop of plot Ep vs log v, the value of 
n can be easily calculated as 0.394. α can be
expressed by Bard and Faulnker24as:
Where
Ep/2 is the potential at half –peak current.So the average value of calculted as 0.197. Further, the number of the
transferred electron (n) was calculated from the αn value as 2 in the SA
electro-oxidation. The value of standard heterogeneous rate constant (k0)
can be calculated by knowing the value of the formal potential (E0)
(from the intercept of the plot Ep versus
ν by extrapolating to the vertical axis at ν=0)26,27. The formal potential (E0) and the
standard heterogeneous rate constant (k0) for the reaction were
obtained as 1.989 and 6.115 
102 s-1 respectively. The
electron transfer rate constant (kox) can be calculated from the
equation28.
kox = k0 × exp {‒ (1‒ α) nF ( E‒ E0) /(RT)}
So the, kox was obtained as 1.540 
103s-1
CONCLUSION:
The aim of this research was to degrade salicylaldehyde with the help of an eco friendly cyclic voltammetry technique. The nature of the reaction is irreversible at platinum electrode and this study suggest that the electro- oxidation of salicylaldehyde found to be two electron transferred and diffusion controlled reaction.
ACKNOWLEDGEMENT:
The author (Jasvinder Kaur) would like to thank the Department of chemistry, Gurukula Kangri (Deemed to be University), Haridwar, India for providing all the necessary facilities for completing this work.
CONFLICT OF INTEREST:
The authors declare no conflict of interst.
REFERENCES:
1. Shahare HV, Bhoyar PK, Dhabarde DM, Jadhav SP, Pawar GM. Phase Transfer Catalytic Synthesis of Aromatic Aldehydes. Research Journal of Pharmacy and Technology.2010; 3(1): 275-276.
2. Joseph L, George M. Analgesic and Anti-Oxidant Activities of Certain (E)-3 Arylidene Flavanones Synthesized by One Pot Method. Asian Journal of Research in Chemistry.2009; 2(3): 318-321.
3. Asadollahi-Baboli M. Straightforward MIA‐QSTR evaluation of environmental toxicities of aromatic aldehydes to Tetrahymena pyriformis. SAR and QSAR in Environmental Research. 2013; 24(12):1041-50.doi.org/10.1080/1062936x.2013.840678
4. Ali A, Merza J. Synthesis and Characterization of Novel Dialdehydes based on SN2 Reaction of Aromatic Aldehyde. Inorganic Chemistry : An Indian Journal . 2017;12(1):111
5. Shanthi S, Stella J. Synthesis, Characterization and Antibacterial Activity of Complexes of Transition Metal Ions with Schiff Base Derived From Salicylaldehyde and p-Methoxy Aniline. Asian Journal of Research in Chemistry.2011; 4(1):84-87
6. Valli G., Ramu K. Mareeswari P. Salicylaldehyde Schiff bases Bioactivity Prediction by Insilico Approach. Asian Journal of Research in Chemistry. 2012; 5(4): 504-509.
7. Wang Y, Jiang H, Tian JJ, He JB. Spectroelectrochemistry of salicylaldehyde oxidation. Electrochimica Acta. 2014 10(125):133-40. doi.org/10.1016/j.electacta.2014.01.087
8. López LJ, Mochón MC, Sánchez JC, Pérez AG. Differential pulse polarographic determination of salicylaldehyde as its Girard-P derivative. Microchimica Acta. 1996; 124(3-4):187-94.doi.org/10.1007/BF01242815
9. Nonyama R, Naito T, Takayanagi M, Goto S, Yashiro T. Colorimetric determination of salicylaldehyde with 1, 3-diphenyl-2-thiohydantoin. Chemical and Pharmaceutical Bulletin. 1987 ; 25;35(3):1281-4.
10. Kiss L, Bősz D, Kovács F, Li H, Nagy G, Kunsági-Máté S. Investigation of phenol electrooxidation in aprotic non-aqueous solvents by using cyclic and normal pulse voltammetry. Polymer Bulletin. 2019;76(11):5849-64.doi.org/10.1007/s00289-019-02678-2
11. Kiss L, Kunsági-Máté S. Electrochemical oxidation of benzaldehyde and hydroxybenzaldehydes in acetonitrile on platinum and glassy carbon electrodes. Comptes Rendus Chimie. 2019 ;22(8):557-61.doi.org/10.1016/j.crci.2019.06.004
12. Matyasovszky N, Tian M, Chen A. Kinetic study of the electrochemical oxidation of salicylic acid and salicylaldehyde using UV/vis spectroscopy and multivariate calibration. The Journal of Physical Chemistry A. 2009;113(33):9348-53. 10.1021/jp904602j
13. Crompton TR. Determination of organic compounds in natural and treated waters. CRC Press; 1999 Oct 14.
14. Patil PS, Kumbhoje SR, Patil SS. Pharmaceutical Waste Management-An Overview. Asian Journal of Pharmaceutical Research. 2015;5(2):118-21. doi: 10.5958/2231-5691.2015.00018.0
15. Kannan D, Mani N. Comparative Study on Chemical analysis of Thanjavur and Nagapattinam region groundwater samples. . Asian Journal of Research in Chemistry. 2021; 14(1):42-46. . doi: 10.5958/0974-4150.2021.00007.9
16. Farghaly OA, Hameed RA, Abu-Nawwas AA. Analytical application using modern electrochemical techniques. International Journal of Electrochemical Science. 2014;9(1):3287-318.
17. Ramalakshmi N, Marichamy B. Sensing of Lead and Copper Metal Ions by Substituted N-Methyl Piperazine Compound on Glassy Carbon Electrode. Asian Journal of Research in Chemistry. 2011;4(12):1920-7.
18. Guediri I, Boubekri C, Smara O, Lanez T. Total phenolic contents and determination of Antioxidant activity by DPPH, FRAP, and cyclic voltammetry of the fruit of Solanum nigrum (black nightshade) growing in the south of Algeria. Asian Journal of Research in Chemistry. 2021 ;14(1):47-55.doi: 10.5958/0974-4150.2021.00008.0
19. Chatterjee A. Different electrodes for paracetamol estimation using cyclic voltammetry technique: A review. Research Journal of Pharmacology and Pharmacodynamics. 2017;9(2):88-92.doi.org/10.5958/2321-5836.2017.00015.5
20. Nicholson RS, Shain I. Theory of stationary electrode polarography. Single scan and cyclic methods applied to reversible, irreversible, and kinetic systems. Analytical chemistry. 1964;36(4):706-23.
21. Lalitha P, Sivakamasundari S. Effect of Variation of Concentration and pH on the Cyclic Voltammetric Behaviour of 4-Methyl-3-Vinyl Quinoline-2 (1h)-One at Glassy Carbon Electrode. Asian Journal of Research in Chemistry. 2010;3(4):1015-9.
22. Nicholson RS. Theory and application of cyclic voltammetry for measurement of electrode reaction kinetics. Analytical Chemistry. 1965; 37(11):1351-5.
23. Wudarska E, Chrzescijanska E, Kusmierek E, Rynkowski J. Voltammetric studies of acetylsalicylic acid electrooxidation at platinum electrode. Electrochimica Acta. 2013;93:189-94.doi.org/10.1016/j.electacta.2013.01.107
24. Allen JB, Larry RF. Electrochemical methods fundamentals and applications. John Wiley & Sons; 2001.
25. Laviron E. General expression of the linear potential sweep voltammogram in the case of diffusionless electrochemical systems. Journal of Electroanalytical Chemistry and Interfacial Electrochemistry. 1979; 101(1):19-28.doi.org/10.1016/S0022-0728(79)80075-3
26. Fotouhi L, Fatollahzadeh M, Heravi MM. Electrochemical behavior and voltammetric determination of sulfaguanidine at a glassy carbon electrode modified with a multi-walled carbon nanotube. International Jounal of Electrochemical Science. 2012;7:3919-28..
27. Wu Y, Ji X, Hu S. Studies on electrochemical oxidation of azithromycin and its interaction with bovine serum albumin. Bioelectrochemistry. 2004; 64(1):91-7.doi.org/10.1016/j.bioelechem.2004.03.005
28. Van Benschoten, JJ, Lewis YT, Heineman WR, RostonDA, Kissinger PT, Cyclic Voltammetry Experiments, Journal of Chemical Education. 1983;60(9):772-76.
Received on 17.04.2021 Modified on 23.05.2021
Accepted on 19.06.2021 © RJPT All right reserved
Research J. Pharm. and Tech. 2022; 15(5):2204-2207.
DOI: 10.52711/0974-360X.2022.00366