I= DISTRIBUTION OF SUBSTITUTED BENZOIC ACIDS BETWEEN WATER AND IMMISCIBLE ORGANIC SOLVENTS
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Title of Thesis
DISTRIBUTION OF SUBSTITUTED BENZOIC ACIDS BETWEEN WATER AND IMMISCIBLE ORGANIC SOLVENTS
Author(s)
Azra Imtiaz
Institute/University/Department Details
Institute of Chemistry, University of the Punjab, Lahore
Session
1984
Subject
Chemistry
Number of Pages
220
Keywords (Extracted from title, table of contents and abstract of thesis)
benzoic acids, organic solvents, salicylic acid, water-carbon-disulphide, water-carbon tetrachloride, water-benzene, water-chloroform, m-hydroxybenzoic acid, p-hydroxybenzoic acid, p-fluorobenzoic acid

Abstract
Partition investigations of O-,m-and p-hydroxyl benzoic acids and p-fluorobenzoic acid have been carried out between aqueous and different immiscible organic co-solvents at seven temperatures from 20.0 to 50.0°C.

SALICYLIC ACID Distribution of salicylic acid between water-carbon-disulphide, water-carbon tetrachloride, water-benzene and water-chloroform pairs has been investigated at seven temperatures between 20° and 50°C. The distribution coefficient (K12,s) of undissociated monomeric salicylic acid between aqueous and organic solvent phases and equilibrium constants .(K12,s) for dissociation of salicylic acid dimers to monomers in organic layers have been evaluated at each of the seven temperatures using Moelwyn-Hughes39 expression (1.27).

K1(H2O-CS2)

Thermodynamic data (∆H°, ∆G°, and ∆S°) for distribution of the acid in each solvent pair and dissociation of the dimerized salicylic acid in each organic .solvent at each temperature have been calculated. The values of distribution and dissociation constants. have been found to increase with rise in temperature in all cases except in water carbon disulphide system, where they show decrease with increase in temperature. These constants are seen to increase with increase in dielectric constant of the solvent as well.

M-HYDROXYBENZOIC ACID Distribution of m-hydroxybenzoic acid between water benzene and water-cyclohexane pairs has been studied at seven temperatures between 20.0° and 50.0°C. The distribution coefficient of dimer m-hydroxybenzoic acid between aqueous and organic solvent phases has been evaluated at each of the seven temperatures. It is quite interesting to observe that m-hydroxybenzoic acid is found to obey √Co/√Cw = K expression showing that the acid exists as a dimer in both the aqueous and organic solvents. The comparison of distribution coefficient of the dimerized acid in the two aqueous organic solvent pairs will show the following increasing order.

K1 (Water-cyclohexane) < K1 (Water-benzene)

Thermodynamic data (∆H°, ∆G°, and ∆S°) for the distribution of the acid in each solvent pair at each temperature have been calculated. The values of distribution constant have been found to increase with rise in temperature in both solvent systems. These constants are also seen to increase with increase in dielectric constant of the solvents.

P-HYDROXYBENZOIC ACID Distribution of p-hydroxybenzoic acid between water-benzene. and water-chloroform pairs has been investigated at seven temperatures between 20.0° to 50.0°C. The distribution coefficients (K1‘s) of monomer p-hydroxybenzoic acid between aqueous. and organic solvent phases and dissociation equilibrium constants (K12 ‘s) for dissociation of p-hydroxybenzoic acid dimer to monomer in organic solvent layers have been evaluated using Moelwyn-Hughes relationship29 and Nernst simplified expression √Co/√Cw = K have also been. used, which show that the acid exists as a dimer in the organic phase, while as a monomer in the aqueous phase. The values of Nernst distribution constants are found much higher than those calculated by Moelwyn -Hughes expression. The comparison of the distribution coefficients and dissociation equilibrium constants will show the following increasing order

K1.(water-benzene) < K1 (water-chloroform) and K12(chloroform) < K12 (benzene)

Thermodynamic data (∆H°, ∆G°, and ∆S°) for distribution of the acid in each solvent pair and dissociation of the dimerized p-hydroxybenzoic acid in each organic solvent at each temperature have been calculated. The values of distribution and dissociation constants have been found to increase with rise in temperature in both the solvents. These constants are again seen to increase with. increase in dielectric constant of the solvent.

p-FLUOROBENZOIC ACID Distribution of p-fluorobenzoic acid between water-carbon tetrachloride, water-cyclohexane, water-benzene and water-chloroform has been studied at five temperatures between 25.0o to 50.0oC. The distribution coefficient (K1‘s) of undissociated p-fluorobenzoic acid between. aqueous and organic phases and equilibrium dissociation constants (K12‘s) for the dissociation of p-fluorobenzoic acid dimer to monomer in organic layers have been evaluated using Moelwyn-Hughes29 Equation (1.24) at each of the five temperatures. They have. been found to vary in. the following order

K1 (Water-cyclohexane) <-K1 (Water-carbon tetrachloride) < K1 (Water-benzene)< K1 (Water-chloroform)

and K12(cyclohexane) < K12(carbon tetrachloride)< K12(benzene)< K12(chloroform)

The distribution behaviour of p-fluorobenzoic acid is found to be similar to that of p-hydroxybenzoic acid. Therefore, Nernst simplified relationship. (√Co/√Cw = K) has again been used in this case. It is seen that the acid exists as a dimer in the organic solvent and as a monomer in water. The values of distribution constants given by Moelwyn -Hughes equation are much smaller than those found by Nernst simplified expression.

Thermodynamic data (∆H°, ∆G°, and ∆S°) for the distribution of the acid in each solvent pair and dissociation of the dimer p-fluorobenzoic acid in each organic solvent at each temperature have been calculated. The values of distribution and dissociation constants have been found to increase with rise in temperature. These constants are seen to increase with increase in dielectric constant of the solvent as well.
Download Full Thesis
1167.11 KB
S. No. Chapter Title of the Chapters Page Size (KB)
1 0 Contents
33.7 KB
2 1 Introduction 1
60.48 KB
  1.1 General 6
3 2 Nernst’s distribution law 23
142.71 KB
  2.1 Deviations 37
  2.2 Applications 37
  2.3 Thermodynamic of partitioning systems 42
4 3 Partition investigation of salicylic acid between waster and immiscible organic solvents at various temperatures 45
278.54 KB
  3.1 Abstracts 45
  3.2 Introduction 46
  3.3 Experimental 48
  3.4 Calculations and results 51
  3.5 Discussion 55
  3.6 Tables 61
  3.7 Figures 83
5 4 Partition investigations of m-hydroxybenzoic acid between water and immiscible organic solvents at various temperatures 92
156.83 KB
  4.1 Abstracts 92
  4.2 Introduction 93
  4.3 Experimental 94
  4.4 Calculations and results 98
  4.5 Discussion 98
  4.6 Tables 105
  4.7 Figures 116
6 5 Partition investigations of p-hydroxybenzoic acid between water and immiscible organic solvents at various temperatures 120
164.67 KB
  5.1 Abstract 120
  5.2 Introduction 121
  5.3 Experimental 121
  5.4 Calculations and results 122
  5.5 Discussion 123
  5.6 Tables 129
  5.7 Figures 142
7 6 Partition investigations of p-fluorobenzoic acid between water and immiscible organic solvents at various temperatures 147
304.25 KB
  6.1 Abstract 147
  6.2 Introduction 148
  6.3 Experimental 148
  6.4 Calculations and results 149
  6.5 Discussion 150
  6.6 Hydrogen bonding in ortho, meta and para-hydroxybenzoic and para-fluorobenzoic acids in organic solvents 156
  6.7 Tables 159
  6.8 Figures 180
  6.9 Bibliography 188