I= PHYSICAL AND KINETIC INVESTIGATION OF MICELLAR EFFECTS ON THE REACTION OF P-NITROPHENYL PROPIONATE WITH HYDROXIDE ION
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Title of Thesis
PHYSICAL AND KINETIC INVESTIGATION OF MICELLAR EFFECTS ON THE REACTION OF P-NITROPHENYL PROPIONATE WITH HYDROXIDE ION

Author(s)
Fouzia Hassan
Institute/University/Department Details
University of Karachi/ Department of Pharmaceutics
Session
1996
Subject
Pharmacy
Number of Pages
273
Keywords (Extracted from title, table of contents and abstract of thesis)
micellar effects, p-nitrophenyl propionate, hydroxide ion, para-nitrophenyl propionate, micelle formation, polysorbates, cmc, pnpp

Abstract
The micellar effect on the hydrolysis of para-nitrophenyl propionate (PNPP), was studied spectrophotometrically at 35°C in basic solution. The applicability of the electrostatic model was tested by determining the effect of differently charged and uncharged micelles on the observed rates of reactions. The effect of ionic surfactant was in the concentration range of 1X10-6M to 8X10-2M. The rates of p-nitrophenol formation by the reaction of PNPP with hydroxide in were also measured in the presence of polysorbates (Tweens) 20,40,60 and 80 between 1-6% w/v. The work was carried out in the presence of carbonate-bicarbonate buffer at pH 9.2. The effect of neutral inorganic electrolytes (sodium chloride, sodium acetate and sodium sulphate) on the rate of hydrolysis of PNPP in the absence and presence of cationic surfactants was also studied

The CMCs of surfactants were determined by different methods. The CMCs were found to be decreased as the hydrophobic part of the surfactants was increased, which could be due to decrease of interfacial energy on micellization which is more longer chain than short ones

It was concluded from the analysis of kinetic data that all cationic surfactants studied in this work increased the rate of hydrolysis of PNPP and the first-order rate constants go through maxima with increasing cationic surfactants in the region of 1X10-2M to 5X10-2M surfactant and then the effect decreased. Changes in micellar structure in this critical region were evidenced by viscosity studies. There was an increase in the viscosity in the order sodium chloride < sodium acetate < Sodium sulphate for all the kinetic profiles was observed for the anionic and nonionic surfactants where the hydrolysis rates were inhibited. The addition of various concentrations of sodium chloride, sodium acetate and sodium sulphate continuously suppress the maxima in the surfactant rate profiles irrespective of salts. The addition of 1.5-2M concedntration of all salts completely eliminated this maxima, which is quite striking effect of these electrolytes. Sodium sulphate was found to be much more potent inhibitor of cationic surfactants catalysis among, sodium chloride and sodium, acetate

The partitioning behavior of PNPP between the micelles and the bulk solution of ionic surfactants was also studied to analyse the kinetic results

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1887.51 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents 0
114.72 KB
2 1 Introduction 1
287.46 KB
  1.1 Micelle Formation Of Surfactants 2
  1.2 Size And Shape Of The Micelle 4
  1.3 Structure Of The Micelle 6
  1.4 Factors Affecting Micellization 10
  1.5 Thermodynamics Of Micelle Formatlion 15
  1.6 The Effect Of Micelles In Chemical Kinetics 23
  1.7 Salt Effect On Micellar Rates 30
3 2 Leterature Review 35
112.4 KB
  2.1 Ester Hydrolysis And Reaction Kinetics 35
  2.2 Kinetics Of Ester Hydrolysis And The Rate Equation 38
4 3 Materials And Methods 49
95.79 KB
  3.1 General Chemicals 49
  3.2 Equipment 57
  3.3 General Procdures 59
5 4 Experimental 62
680.52 KB
  4.1 Measurement Of Critical Micelle Concentration 62
  4.2 Kinetics Of The Hydrolysis Of P- Nitrophenyl Propionate ( Pnpp ) 83
  4.3 General Procedure For Kinetic Studies 88
  4.4 Determination Of The Reproducibility Of Experimental Technique 89
  4.5 Effect Of Concentration Of Ionic And Nonionic Surfactants On Hydrolysis 101
  4.6 Effect Of Salt On The Rate Of Hydrolysis Of Pnpp 116
6 5 Viscosity Studies On CTAB Systems 145
70.51 KB
  5.1 Experimental Procedure 150
  5.2 Cleaning Of Viscometers 151
  5.3 Measurement Of Viscosity On CTAB Solution 151
7 6 Viscosity data of CTAB in distilled water only 189
673.05 KB
8 7 Conslusion 250
184.09 KB
  7.1 Suggestions 251
  7.2 References 253