International Journal of Science and Research (IJSR) ISSN: 2319-7064 ResearchGate Impact Factor (2018): 0.28 | SJIF (2018): 7.426 Volume 9 Issue 1, January 2020 www.ijsr.net Licensed Under Creative Commons Attribution CC BY Kinetics and Mechanism of Hydrolysis of O-Hydroxy Benzaldehyde - Aniline Spectrophotometrically Anil S. Kirdant 1 , Bhausaheb K. Magar 2 1 Department of Chemistry, Baburaoji Adaskar Mahavidyalaya, Kaij Dist. Beed, Maharashtra, India 2 Department of Chemistry, Shivaji Arts Commerce and Science College, Kannad, Dist. Aurangabad, Maharashtra, India Abstract: Kinetics of hydrolysis reaction of the Schiff base, Ortho Hydroxy Benzaldehyde - aniline (HL) have been studied in the pH range 2.86-12.30 at temperature range 293-308 K. A rate profile diagram of pH v/s rate constant shows the rate minimum in the pH range 5.21-10.22 and reaches a plateau at pH > 10.73. Suitable reaction mechanism has been suggested for the hydrolysis of the Schiff base in acidic, neutral and basic medium. From the effect of temperature on the rate, various thermodynamic parameters have been evaluated. Keywords: Schiff base, hydrolysis, kinetics, Spectrophotometry 1. Introduction The Schiff bases are also called imines. The study of formation and hydrolysis of Schiff base is an important reaction of biochemical interest 1-4 . The hydrolysis and formation of Schiff bases is important due to its relevance to the transformation of >C = O to >C = N and vice versa 5-9 . The catalytic effect of hydrogen, hydroxyl and metal ions on the formation and hydrolysis of imines have been studied by several workers 10-12 .In the present work we represented here systematic study of the hydrolysis of Schiff base, O- Hydroxy Benzaldehyde - aniline at different pH values. 2. Materials and Method Experimental: The chemicals used such as, O-Hydroxy Benzaldehyde,- aniline, ethanol etc. were of AR grade. The Schiff base was prepared by condensation reaction of, O- Hydroxy Benzaldehyde - aniline in ethanol medium for about three hour. On cooling the resulting yellow coloured crystals were recrystalised from ethanol, melting point = 50 0 C. Purity was checked by TLC. Kinetic measurements: The rate of hydrolysis of Schiff base was followed spectrophotometrically at 434 nm by using UV/VIS, 1601, Shimadzu Spectrophotometer. Universal buffer solutions were prepared according to the reported methods 13 .The pH was determined by using an Elico LI-120 pH meter. The temperature was varied between 293– 308 K. The concentration of imine was kept at 1 X 10 -4 mol dm -3 . The ionic strength of the reaction mixture was maintained at  = 0.1 mol dm -3 by using KCl. All chemicals used were of A.R. grade. In a typical kinetic run, the solutions containing appropriate amounts of Schiff base and buffer solution were prepared at room temperature and allowed to equilibrate in previously adjusted thermostat. The quartz cuvettes were also allowed to equilibrate at the same temperature in the thermostatic cell block. After mixing, the reaction mixture was immediately transferred to a quartz cell and the decrease of absorbance of Schiff base with time was followed against the reagent blank kept in another quartz cell. The decrease of absorbance with time was followed at  = 434 nm. Using spectrophotometer within 20 s of mixing the Schiff base. The plot of log (A t -A  ) vs time were found to be straight lines and pseudo first order rate constants were calculated from the slopes. From the effect of temperature on the reaction rate, energy of activation E, and other thermodynamic parameters were evaluated. 3. Results and Discussion The rate constant values in the pH range 2.86-12.30 at 303 K are listed in Table-1. A rate profile diagram of pH v/s rate constant at 303 K and ionic strength  = 0.1 mol dm -3 shows the rate minimum at 5.21<pH < 10.22 (Figure. 1). Table 1: Rate constant data hydrolysis of Ortho Hydroxy Benzaldehyde - aniline Ethanol – water = 40 % (v/v), Temp. = 303K, μ = 0.1 mol dm -3 . pH [H + ] x 10 6 mol dm - 3 [OH - ] x 10 6 mol dm -3 k x 10 3 S -1 2.86 13800.00 51.485 3.16 6918.00 29.004 4.51 2630.00 1.380 5.21 61.66 1.072 6.61 1.95 0.783 8.40 2.53 0.641 10.22 1660.00 0.982 10.42 2630.00 1.276 10.73 5370.00 4.700 11.15 14130.00 8.732 12.30 19250.00 9.818 Paper ID: ART20204267 DOI: 10.21275/ART20204267 1134