FORMATION OF SCHIFF’S BASE (ACACEN) USING ETHYLENEDIAMINE AND EFFECT OF PH ON ZINC (II) ION ON COATED SILICA GEL BY COLUMN METHOD

FORMATION OF SCHIFF’S BASE (ACACEN) USING ETHYLENEDIAMINE AND EFFECT OF pH ON ZINC (II) ION ON COATED SILICA GEL BY COLUMN METHOD

ABSTRACT

Acetylacetone ethylenediamine (ACACEN) is a Schiff base resulting from the condensation of pentan-2,4-dione and 1,2-diaminoethane. Solid-phase extraction of Zn (II)  by column method in the pH range 1-12 have been studied in trichloromethane using acetylacetone ethylenediamine (ACACEN). Zn (II) extraction using 2% ACACEN in CHCl₃ is sufficient or abundant in the pH of 5.0. The aqueous ACACEN shows a maximum absorption at 320nm.The Zn (II) complex has maximum absorption at 572nm.The acid dissociation constants of H₂B (ACACEN) are obtained of by titrating with 0.179M NaOH and are found to be pKai_D = 11.55 and PKa_2D = 11.55 corresponding to the formation of HB^– and B2 respectively. pKa_ID and pKa_2D share the common value since H₂B (ACACEN) has two ionizable hydrogen atoms located in the same chemical environment. Electronic spectrum of ACACEN suggests that ACACEN absorbs maximally in the ultraviolet regions of the spectrum and not in the visible region since it is not displayed in the spectrum. The physical modification of the silica gel using ACACEN has also been studied. The optimal pH value is found at the pH5.

TABLE OF CONTENT

Title page                                                                        i

Certification page                                                            ii

Dedication page                                                              iii

Acknowledgement                                                           iv

Abstract                                                                           v

Table of contents                                                            vi

CHAPTER ONE

1.0 Introduction                                                               1

1.1 Background of the study                                            1

1.2 Objectives of the study                                               3

1.3 Statements of the problem                                        4

1.4 Hypotheses of the study                                             5

1.5 Significance of the study                                            5

1.6 Limitation of the study                                               6

CHAPTER TWO

2.0 Literature review                                                                7

2.1 Metal ion under study zinc (II) ion                             10

2.1.1 Uses/properties of zinc                                           10

2.2  Solid phase extraction                                              11

2.3 Mechanism of solid phase extraction process            13

2.4 Solid phase extraction process                                  19

2.5 Sorbent in SPE                                                          22

2.6 Coupling Solid Phase Extraction with various

Techniques                                                                        37

    CHAPTER THREE

3.0 Materials and Method                                                40

3.1 Materials                                                                    40

3.1.1 Instruments/Equipment                                         40

3.1.2 Chemical reagents                                                  41

3.2 Methods                                                                     46

3.2.1 Synthesis of the Schiff’s base acetylacetone

ethlylenediamine(ACACEN).                                     46

3.2.2 Activation of silica gel                                             47

3.2.3 Preparation of stock solution of the ligand,

acetlyacetone ethylenediamine                                        47

3.2.4 Preparation of the buffer solutions (pH1- pH 12)    48

3.2.5 Preparation of immobilized Schiff’s base

(ACACEN) silica gel                                                 48

3.2.6 Preparation of the extraction column                      49

3.2.7 Effect of pH on the modified silica gel                     49

3.2.8 Determination of the acid dissociation constant

of the ACACEN                                                         50

3.2.9  Determination of wavelength of maximum

absorbance (⋋max) of aqueous ACACEN                         51

CHAPTER FOUR

4.0 Result and Discussion                                               52

4.1 Results                                                                      52

4.1.1 Activation of silica gel                                             52

4.1.2 Properties of ACACEN                                             52

4.1.3 Electronic spectrum of ACACEN                             53

4.1.4 Acid dissociation constants of ACACEN                          54

4.1.5 Effect of sample volumes on modified silica gel      55

4.2 Discussion                                                                 56

4.2.1 Activation of silica gel                                             56

4.2.2 Properties of ACACEN                                             56

4.2.3 Electronic spectrum of ACACEN in aqueous

solution                                                                  57

4.2.4 Acid dissociation constants of ACACEN                  57

CHAPTER FIVE

5.0 Conclusion and Recommendation                             59

5.1Conclusion                                                                 59

5.2 Recommendation                                                      60

References                                                                      61

CHAPTER ONE

1.0      INTRODUCTION

1.1      BACKGROUND OF THE STUDY

Schiff’s bases are important class of organic compounds (Arulmurugan et al., 2010). They were first reported by Hugo Schiff in 1864. Schiff’s bases are condensation products of primary amines with carbonyl compounds. The common structural feature of these compounds is the azomethine group with the general formula RHC=N-R_1,where R and R₁ are alkyl, aryl, cycloalkyl or heterocyclic groups (Arulmurugan et al., 2010). Structurally, a Schiff’s base (also known as imine or azomethine) is a nitrogen analogue of an aldehyde or ketone in which the carbohyl group (>C=O) is replaced by an imine or azomethine group. Schiff’s bases have also been shown to exhibit a broad range of biological activities, including antifungal, antibacterial, antimalarial, anti-inflamatory, antiviral and antipyretic properties (Przybylski et al., 2009). Imine or azomethine groups are present in various natural, naturally derived and non-naturally compounds. The imine group present in such compounds has been shown to be critical to their biological activities (Guo et al., 2007). Schiff’s bases are important compounds owing to their wide range of industrial applications (Li et al., 2003). Schiff’s bases are used in the photostabilization of poly (vinyl chloride) polymers against photodegradation by ultraviolet radiation (Yousif et al., 2011) are also used to improve poly(methyl methacrylate) from degradation (Yousif et al,. 2012) and to prevent polystyrene from photodegration by their addition to polymer films (Yousif et al., 2012).

Acetylacetone is an organic compound that famously exists in two tautomeric forms that rapidly interconvert. The pair of tautomers rapidly interconvert and are treated as a single compound in most applications. Although the compound is formally named as the diketone form, pentane-2,4-dione, the end form forms a substantial component of the material and is actually the favoured form in many solvents. It is a colourless liquid that is precursor to acetylacetonate (acac), a common bidentate ligand. It is also a building block for the synthesis of heterocyclic compound.

The keto and enol forms of acetylacetone coexist in solution; these forms are tautomers. The end form has the hydrogen shared equally between the two oxygen atoms in the gas phase, the equilibrium constant, Keto-enol is 11.7, favoring the end form. The two tautomeric forms can easily be distinguished by NMR spectroscopy, IR spectroscopy and other methods.

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