Download Lecture 20.The d-Block Elements.VII

LECTURE 20. THE D-BLOCK ELEMENTS.
VII-VIII B GROUPS
PhD. Halina Falfushynska
MANGANESE
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Manganese is obtained mainly from the mineral
pyrolusite, MnO2.
Ferromanganese alloys are wear resistant and
shock resistant and are used for railroad tracks,
bulldozers, and road scrapers.
Manganese(IV) oxide is the starting point for
making most other manganese compounds.
Potassium permanganate, KMnO4, is an important
oxidizing agent that is used in both analytical and
organic chemistry laboratories, and in water
treatment.
THE IRON TRIAD: FE, CO, AND NI
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Iron is the fourth most abundant element in Earth’s
crust. Cobalt and nickel are not nearly as common.
All three elements form 2+ and 3+ ions.
The most common ions of Co and of Ni are the 2+. The
most common ion of Fe is the 3+ due to the half-filled dsubshell:
FERROMAGNETISM
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The iron triad exhibits ferromagnetism which is a much
stronger magnetic effect than paramagnetism.
A ferromagnetic solid consists of regions called domains in
which atoms have their magnetic moments aligned.
• When placed in a
magnetic field, all
the domains are
aligned and the solid
becomes
magnetized.
Examples of variable oxidation states in the transition
metals
Iron
Iron has two common oxidation states (+2 and +3) in, for
example, Fe2+ and Fe3+. It also has a less common +6
oxidation state in the ferrate(VI) ion, FeO42-.
Manganese
Manganese has a very wide range of oxidation states in its
compounds. For example:
+2 in Mn2+
+3 in Mn2O3
+4 in MnO2
+6 in MnO42+7 in MnO4-
Thinking about a typical transition metal (iron)
Here are the changes in the electronic structure of iron
to make the 2+ or the 3+ ion.
Fe
[Ar] 3d64s2
Fe2+
[Ar] 3d6
Fe3+
[Ar] 3d5
The 4s orbital and the 3d orbitals have very similar
energies. There isn't a huge jump in the amount of
energy you need to remove the third electron compared
with the first and second.
The figures for the first three ionisation energies (in kJ
mol-1) for iron compared with those of calcium are:
metal
1st IE
2nd IE
3rd IE
Ca
590
1150
4940
Fe
762
1560
2960
There is an increase in ionisation energy as you take
more electrons off an atom because you have the same
number of protons attracting fewer electrons.
Manganese
Mn
(Manganum)
trace element
- cofactor of enzymes:
superoxide dismutase
pyruvate carboxylase
KMnO4
Potassium permanganate
(INN: Kalii
permanganas)
- in water dissolves to give deep
purple solutions
- strong oxidizing agent
- dilute solutions can act as desinfectant
Iron
Fe
(Ferrum)
important microelement
human body: 4–5 g Fe
a) functional form
- heme iron proteins
hemoglobin
70 %
myoglobin
5%
some enzymes
- non-heme iron proteins
b) tranport form (transferrin)
c) storage of iron (ferritin, hemosiderin)-20 %
Fe in food 10-30 mg/day absorption: only 710%  ~ 1 mg/day
HEME iron proteins
Hemoglobin
- O2 transport in blood
- in red blood cells
- tetramer = 4 subunits
(each subunit: one heme + one globin)
HbA
HbF
("adult")
("fetal")
a2b2
a2g2
Myoglobin - "O2 storage" in muscle cell
Cytochromes - electron transport
(oxidized)
- their function is based on:
heme
Fe2+ (reduced)
Fe3+
Non-heme iron proteins FeII
or FeIII bound to protein
SH
iron–sulphur proteins (FeS proteins)
Transferrin
- blood plasma protein ( b1 globulin )
- transport of Fe
- 1 molecule of transferrin can carry 2 iron ions in form of Fe3+
Ferritin - intracellular iron storage protein (liver, bone marrow)
- 1 ferritin complex can store about 4500 Fe3+
- ferritin without iron = apoferritin
Hemosiderin - "damaged (Fe-overloaded) ferritin" - Fe from it is less available
OVERVIEW OF IRON METABOLISM
FOOD
tissues
CYTOCHROMES
Fe-S proteins
liver
FERRITIN
HEMOSIDERIN
blood plasma
TRANSFERRIN
bone marrow
FERRITIN
muscles
MYOGLOBIN
spleen
FERRITIN
red blood cells
HEMOGLOBIN
BLEEDING (Fe losses)
Iron metabolism = unique
- reutilization !
(closed system)
NO regulated excretion system for Fe !
Fe absorption must be "regulated"
Loss of Fe  through loss of blood (females
- mestrual bleeding)
Iron deficiency - microcytic anemia "iron deficiency anemia"
Iron overload
- hemochromatosis = accumulation of iron in the body
(depositions as hemosiderin)
organ dysfunction (liver, heart, ...)
IRON ABSORPTION
FOOD Fe3+
STOMACH
HCl pH 1-2
ascorbic acid
gastroferrin - iron binding protein
reduction
Fe2+
Fe3+
apoferritin
ferritin
(Fe3+)
INTESTINAL MUCOSA CELL
Fe2+
BLOOD
transferrin (Fe3+)