Manganese Experiment
UNIVERSITY OF ZIMBABWE
Programme Bscd (ІІ)
Course CH202
Practical Number 4 Title d-block elements- Manganese
AIMS /OBJECTIVES * To understand the reactions of manganese * To prepare Mn(acac)3 and calculate percentage yield * To calculate the percentage of Mn and acetyl acetone and the empirical formula
THEORY
Manganese is a first row transition metal that has a tremendous variety of oxidation states that appear in its compounds. The oxidation numbers range from Mn (III) in compounds like Mn(NO)3CO to Mn (VII) in KMnO4. Compounds of manganese range in oxidation number between theses two extremes. This experiment involves the preparation of a Mn (III) complex of actylacetone (also named 2,4-pentanedione) which is a useful starting material for the preparation of other Mn (III) compounds. Manganese (III) complexes are relatively stable and can be prepared directly by reactions of the hydrous manganese (III) oxide or by oxidation of the hydrous manganese (II) oxide with air or an oxidizing agent.(Pass,1997) In aqueous solution Mn(III) is readily hydrolyzed
Mn3+ + 2 H2O →Mn(OH)2 + H+ and is most stable in acid solutions. Manganese (III) is also slowly reduced by water.(Liptrot,1993)
4 Mn3+ + 2 H2O → 4 Mn2+ + 4H+ + O2
Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion and metal ions, usually transition metals. The ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl. Many such complexes are soluble in organic
Programme Bscd (ІІ)
Course CH202
Practical Number 4 Title d-block elements- Manganese
AIMS /OBJECTIVES * To understand the reactions of manganese * To prepare Mn(acac)3 and calculate percentage yield * To calculate the percentage of Mn and acetyl acetone and the empirical formula
THEORY
Manganese is a first row transition metal that has a tremendous variety of oxidation states that appear in its compounds. The oxidation numbers range from Mn (III) in compounds like Mn(NO)3CO to Mn (VII) in KMnO4. Compounds of manganese range in oxidation number between theses two extremes. This experiment involves the preparation of a Mn (III) complex of actylacetone (also named 2,4-pentanedione) which is a useful starting material for the preparation of other Mn (III) compounds. Manganese (III) complexes are relatively stable and can be prepared directly by reactions of the hydrous manganese (III) oxide or by oxidation of the hydrous manganese (II) oxide with air or an oxidizing agent.(Pass,1997) In aqueous solution Mn(III) is readily hydrolyzed
Mn3+ + 2 H2O →Mn(OH)2 + H+ and is most stable in acid solutions. Manganese (III) is also slowly reduced by water.(Liptrot,1993)
4 Mn3+ + 2 H2O → 4 Mn2+ + 4H+ + O2
Metal acetylacetonates are coordination complexes derived from the acetylacetonate anion and metal ions, usually transition metals. The ligand acetylacetonate is often abbreviated acac. Typically both oxygen atoms bind to the metal to form a six-membered chelate ring. The simplest complexes have the formula M(acac)3 and M(acac)2. Mixed-ligand complexes, e.g. VO(acac)2, are also numerous. Variations of acetylacetonate have also been developed with myriad substituents in place of methyl. Many such complexes are soluble in organic