Polyethylene is the most widely used polymer.
The long linear chain version is called high
density polyethylene (HDPE) (d = 0.97 g/ml).
It is hard, tough, and rigid. Used for milk and
detergent containers.
2521
The branched chain version is called low
density polyethylene (LDPE) (d=0.92 g/ml).
The branched chains of polyethylene prevent
close packing – hence the density is lower.
2522
The branched chain version is called low
density polyethylene (LDPE) (d=0.92 g/ml).
The branched chains of polyethylene prevent
close packing – hence the density is lower.
This polymer is soft and flexible. Used for
grocery bags, bread bags, etc.
2523
The cross linked polymer is called cross-linked
polyethylene (CLPE). This is a very tough
material. Used for plastic caps on soft drink
bottles.
2524
2525
Condensation Polymers
2526
Condensation Polymers
A condensation reaction occurs when two
molecules react by splitting out or eliminating
a small molecule such as water.
2527
Ester formation reaction:
CH3CO2H + CH3CH2OH
acetic acid
ethanol
CH3CO2CH2CH3 + H2O
ethyl acetate
O
O
2
H O
O
H O
C
Polyesters
C
terephthalic acid
O H
+2 H_ O _ CH2 _ CH2 _ O _H
ethylene glycol
O
C
O
C
_ O _ CH _ CH _ O _ C
2
2
+2 H2O
O
C
O
CH2
CH2
O H
2529
O
O
C
2
H O
O
C
terephthalic acid
O H
+2 H_ O _ CH2 _ CH2 _ O _H
ethylene glycol
O
C
H O
Polyesters
O
C
_ O _ CH _ CH _ O _ C
2
2
+2 H2O
Now consider another terephthalic acid molecule
reacting with the indicated alcohol functional group.
O
C
O
CH2
CH2
O H
2530
O
O
C
O
C
_ O _ CH _ CH _ O _
2
2
n
This is an example of the repeat unit for a polyester. In
this case it is poly(ethylene terephthalate) called PET.
2531
The Transition Elements
Coordination Chemistry
2532
General Characteristics
There are several properties that many of the
transition elements have in common. They
generally tend to be hard and to have high melting
points.
2533
General Characteristics
There are several properties that many of the
transition elements have in common. They
generally tend to be hard and to have high melting
points. Several are essential for life.
2534
2535
General Characteristics
There are several properties that many of the
transition elements have in common. They
generally tend to be hard and to have high melting
points. Several are essential for life.
Another general characteristic of the transition
metals is the occurrence of multiple oxidation
states.
2536
The +2 oxidation state is common to many of the
transition elements because the atoms have a pair
of electrons in their outermost s subshell:
2537
The +2 oxidation state is common to many of the
transition elements because the atoms have a pair
of electrons in their outermost s subshell:
Mn [Ar]3d54s2
Fe [Ar]3d64s2
Co [Ar]3d74s2
2538
The +2 oxidation state is common to many of the
transition elements because the atoms have a pair
of electrons in their outermost s subshell:
Mn [Ar]3d54s2
Fe [Ar]3d64s2
Co [Ar]3d74s2
The underlying 3d subshell is fairly close in energy to
the 4s subshell – not very much energy is needed to
remove still another electron to give a +3 charge.
2539
W
O
I
2540
2541
2542
Another property of the transition metals is the
tendency of their ions to combine with neutral
molecules or anions to form complex ions
(coordination compound):
2543
Another property of the transition metals is the
tendency of their ions to combine with neutral
molecules or anions to form complex ions
(coordination compound):
Cu2+(aq) + 4 NH3(aq)
Cu(NH3)42+(aq)
2544
Another property of the transition metals is the
tendency of their ions to combine with neutral
molecules or anions to form complex ions
(coordination compound):
Cu2+(aq) + 4 NH3(aq)
pale blue
Cu(NH3)42+(aq)
deep blue
2545
2546
Across a period, there is only a relatively small
change in atomic size because the outer s electrons
are shielded quite well from the gradually
increasing nuclear charge – by the electrons that
are being added to the underlying d subshell.
2547
Complex Ions
2548
Complex Ions
Coordination compounds: Compounds formed by a
Lewis acid-base reaction in which a metal atom or
ion is the electron acceptor.
2549
Complex Ions
Coordination compounds: Compounds formed by a
Lewis acid-base reaction in which a metal atom or
ion is the electron acceptor.
Cu2+(aq) + 4 :NH3(aq)
Cu(NH3)42+(aq)
2550
Complex Ions
Coordination compounds: Compounds formed by a
Lewis acid-base reaction in which a metal atom or
ion is the electron acceptor.
Cu2+(aq) + 4 :NH3(aq)
Cu(NH3)42+(aq)
NH3
H3N :
Cu
NH3
: NH3
2551
Ligands: The molecules or ions surrounding the
metal ion in a complex. In Cu(NH3)42+ the NH3
molecules are the ligands.
2552
Ligands: The molecules or ions surrounding the
metal ion in a complex. In Cu(NH3)42+ the NH3
molecules are the ligands.
Donor atom: The atom in a ligand that is bound to
the metal. In the complex Cu(NH3)42+ it is the N
atom.
2553
Coordination number: The number of donor atoms
bound to the central metal atom in a complex.
2554
Coordination number: The number of donor atoms
bound to the central metal atom in a complex.
Examples: Al(H2O)63+ coordination number = 6
2555
Coordination number: The number of donor atoms
bound to the central metal atom in a complex.
Examples: Al(H2O)63+ coordination number = 6
Cu(NH3)42+ coordination number = 4
2556
Coordination number: The number of donor atoms
bound to the central metal atom in a complex.
Examples: Al(H2O)63+ coordination number = 6
Cu(NH3)42+ coordination number = 4
Ag(NH3)2+ coordination number = 2
2557
Naming Coordination Compounds
2559
Naming Coordination Compounds
Rules
2560
Naming Coordination Compounds
Rules
1. The cation is named before the anion.
2561
Naming Coordination Compounds
Rules
1. The cation is named before the anion.
2. Within a complex ion, which will be indicated by
[ ], name the ligands in alphabetical order. Note:
the prefixes do not alter the alphabetical order.
2562
Naming Coordination Compounds
Rules
1. The cation is named before the anion.
2. Within a complex ion, which will be indicated by
[ ], name the ligands in alphabetical order. Note:
the prefixes do not alter the alphabetical order.
3. Anionic ligands end with an o, e.g. chloride
becomes chloro (see the list of ligands for other
examples).
2563
Naming Coordination Compounds
1.
2.
3.
4.
Rules
The cation is named before the anion.
Within a complex ion, which will be indicated by
[ ], name the ligands in alphabetical order. Note:
the prefixes do not alter the alphabetical order.
Anionic ligands end with an o, e.g. chloride
becomes chloro (see the list of ligands for other
examples).
Prefixes are used to indicate when there is more
than one of the same type of ligand, e.g. di for
two, tri for three, etc. (see the list below).
2564
Rules (cont.)
5. If the ligand has a prefix as part of the name, e.g.
ethylenediamine, then the number of such ligands
present is named with a different prefix. The
prefixes are bis for 2, tris for 3, etc. (see the list
below).
2565
Rules (cont.)
5. If the ligand has a prefix as part of the name, e.g.
ethylenediamine, then the number of such ligands
present is named with a different prefix. The
prefixes are bis for 2, tris for 3, etc. (see the list
below).
6. If the complex ion is an anion, the ending ate is
used.
2566
Rules (cont.)
5. If the ligand has a prefix as part of the name, e.g.
ethylenediamine, then the number of such ligands
present is named with a different prefix. The
prefixes are bis for 2, tris for 3, etc. (see the list
below).
6. If the complex ion is an anion, the ending ate is
used.
7. The oxidation number is written when needed
after the metal. Roman numerals are used.
2567
Rules (cont.)
8. For naming complex ions which are anions, the
metal is named using a Latin root, when that is
available. This is probably the hardest item to deal
with.
2568
Some examples
2569
Some examples
1. [Fe(H2O)6](NO3)3
2570
Some examples
1. [Fe(H2O)6](NO3)3
The complex ion is [Fe(H2O)6]3+
2571
Some examples
1. [Fe(H2O)6](NO3)3
The complex ion is [Fe(H2O)6]3+
The compound is hexaaquairon (III) nitrate
2572
Some examples
1. [Fe(H2O)6](NO3)3
The complex ion is [Fe(H2O)6]3+
The compound is hexaaquairon (III) nitrate
2. [Fe(H2O)4Cl2]Cl
2573
Some examples
1. [Fe(H2O)6](NO3)3
The complex ion is [Fe(H2O)6]3+
The compound is hexaaquairon (III) nitrate
2. [Fe(H2O)4Cl2]Cl
Note in this example that there is one Cl as the
anion Cl- and two that are bound to the central
metal ion.
2574
Some examples
1. [Fe(H2O)6](NO3)3
The complex ion is [Fe(H2O)6]3+
The compound is hexaaquairon (III) nitrate
2. [Fe(H2O)4Cl2]Cl
Note in this example that there is one Cl as the
anion Cl- and two that are bound to the central
metal ion.
The name of this compound is
tetraaquadichloroiron (III) chloride
2575
3. [Co(en)3](ClO3)3
2576
3. [Co(en)3](ClO3)3
Here en is the standard abbreviation for
ethylenediamine.
2577
3. [Co(en)3](ClO3)3
Here en is the standard abbreviation for
ethylenediamine. Note there is a prefix as part of
the name of this ligand, so the prefix tris (for 3)
must be used.
2578
3. [Co(en)3](ClO3)3
Here en is the standard abbreviation for
ethylenediamine. Note there is a prefix as part of
the name of this ligand, so the prefix tris (for 3)
must be used. The name of this compound is
tris(ethylenediamine)cobalt (III) chlorate.
2579
4. Na2[ZnCl4]
2580