Download polymer

Chapter 18. Macromolecules
18.1 Starting Materials for
Polymers
18.2 Free Radical Polymerization
18.3 Condensation Polymerization
18.4 Types of Polymers
18.5 Carbohydrates
18.6 Nucleic Acids
18.7 Proteins
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.1 Starting Materials for Polymers
Learning objective:
Describe functional groups and linkage groups in polymers
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.1 Starting Materials for Polymers
 What is a polymer?
A polymer is a macromolecule constructed by linking together
many copies of much smaller molecules called monomers.
 Monomers are organic molecules characterized by their
functional groups.
 Functional groups – specialized groups of atoms that impart a
specific chemical function.

Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polymerizable Functional Groups
 Functional groups are only a part of an organic
molecule.
 R – represents the less important part of the molecule,
and can be H or an organic fragment containing carbon
atoms
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Examples of Alcohols and a Thiol
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Ammonia and Amines
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
The Carbonyl and Carboxyl Groups
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Important Polymer Linkage Groups
…and phosphate
linkages
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.2 Free Radical Polymerization
Learning objective:
Describe polymers made by free radical polymerization
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.2 Free Radical Polymerization
e.g. the synthesis of polyethylene is a three-step sequence
Initiation – a reactive chemical attacks the p bond of a single
ethylene molecule.
 Propagation – the product from step 1 reacts readily with the p
bond of another ethylene molecule. Several of these steps
occur, building a long chain.
 Termination – chain growth comes to an end when two long
chains join.

Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
 Initiation – an initiator molecule is added to ethylene, with
heating, a free radical is formed and the first step occurs

Propagation – the first step leaves a carbon atom with a
free radical, ready for another addition of ethylene
 Termination – the process ends when two radicals collide
and react.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Important Polymers made from Alkenes
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 1 Drawing the
Structure of a Polymer
Polyacrylonitrile, known commercially as Orlon, is made
by polymerizing acrylonitrile (see Figure 18 – 3). Orlon
is used to make fibers for carpeting and clothing. Draw
the Lewis structure of polyacrylonitrile, showing at least
three repeat units.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Rubber
 Polyisoprene – the first alkene polymer to be used in society,
came from sap of rubber trees.
 Now, several forms of rubber are commercially produced by
polymerizing mixtures of two different monomers to give
copolymers.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Cross-linking
 How are rubbers made durable and strong if polymers
are long chain molecules? Wouldn’t they only be held
together by weak intermolecular forces?
 They are chemically treated to create covalent bonds
between the long chain molecules.
 This process is referred to as cross-linking.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.3 Condensation Polymerization
Learning objective:
Describe polymers made by condensation polymerization
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.3 Condensation Polymerization
 Condensation reaction: the formation of a bond
between two molecules eliminating water or some
small molecule.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polyamides
 Amide – a condensation of an amine and a carboxylic
 Polyamides – polymers that contain amide linkage
groups
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polyamides
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polyesters
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 2 The Structure of a Polyamide
Qiana, a polyamide that feels much like silk, has the
following structure:
Identify the monomers used to make Qiana
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polyesters
 Comprise largest segment of market of synthetic fibers
(40%)
 Poly(ethylene terephthalate) is the leading polymer
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.4 Types of Polymers
Learning objective:
Recognize and describe some properties of plastics,
fibres, and elastomers
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.4 Types of Polymers
 Polymers can be divided into three categories based on
their form and resistance to stretching:
Plastics
 Fibers
 Elastomers

Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Plastics
 Plastic is a type of polymer that hardens on cooling or
evaporation of the solvent.

Thermoplastics – plastics that melt or deform when heated
High Density Polyethylene (HDPE) – very rigid and strong, used to make
bottle caps, toys, cabinets for electronic devices
 Low Density Polyethylene (LDPE) – soft, semi-rigid, used to make
plastic bags, squeeze bottles


Thermosetting – plastics that retain their structural integrity
when heated

Formica
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Plasticizers
 Improve the flexibilities of some plastics
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Fibres
 Synthetic fibres are thin
threads of polymer made by
forcing a fluid thermoplastic
material through a set of tiny
pores.
 The polar functional groups
produce strong dipolar forces
that add significant strength to
the material.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Elastomers
 A flexible polymer that can be distorted.
 Most contain alkenes (double bonds)
 The polymer chains are held together by cross-links.
 The number of cross-links will determine the degree of flexibility and
the strength of the polymer.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Effects of Cross-Linking on Rubber
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Recycling Polymers
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.5 Carbohydrates
Learning objective:
Recognize and draw structures of monosaccharides and
polysaccharides
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.5 Carbohydrates
 Carbohydrates are monomers and macromolecules with
empirical formulas of Cx(H2O)y where x and y are integers.
 Important food source for most organisms
 Monosaccharides: small molecules that when broken down
provide quick energy for cells (sugar high)
 Glucose, sucrose, fructose
 Polysaccharides – macromolecular carbohydrates that store
large amounts of energy
 Glycogen, cellulose, chitin
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Monosaccharides
• Have a formula of (CH2O)n where n is 3, 4, 5, or 6.
• The most important ones contain 5 carbons or 6 carbons in a
ring.
• Monosaccharides are cyclic compounds with an oxygen
atom forming an ether linkage in one of the ring positions.
• The carbons are numbered for identification purposes.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 3 Monosaccharide Structures
Describe the differences in structures of ribose and
fructose
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 4 Drawing Monosaccharides
The six-carbon sugar a-galactose is identical to a-glucose
except at carbon atom number 4, where the
orientations are different. Draw the molecular
structure of a-galactose. Simplify the structure using
flat rings rather than the true three-dimensional forms.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Disaccharides
 Formed by the condensation reaction of two
monosaccharides.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 5 Decomposing a Sugar
Whereas humans can obtain energy from sucrose, insects
obtain energy from trehalose, whose line structure
follows. Identify the monosaccharides from which
trehalose is constructed.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polysaccharides
 Macromolecules made up of linked monosaccharides
have two main functions:
To act as structural materials (cellular make up)
 To act as reservoirs for energy

Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polysaccharides
Cellulose and Starch –
both are made from
glucose monomers
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.6 Nucleic Acids
Learning objective:
Draw primary and secondary structures of DNA and RNA
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.6 Nucleic Acids
 The instructions for self-replication in biological
organisms is stored and transmitted by
macromolecules called nucleic acids
 Genetic information is stored in molecules of DNA
(deoxyribonucleic acid) located in the cell nuclei. (M >
109 g/mol)
 The information stored in DNA is transmitted by RNA
(ribonucleic acid). (M = 20,000 – 40, 000 g/mol)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Building Blocks of Nucleic Acids
A nitrogen containing organic base
1.
•
•
Purines: two-ring structures, adenine and guanine
Pyrimidines: one-ring structures, thymine (only in DNA),
cytosine (in DNA and RNA) and uracil (only in RNA)
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Building Blocks of Nucleic Acids
A pentose sugar
2.
•
•
3.
RNA - ribose
DNA – deoxyribose
A phosphate linkage
derived from phosphoric
acid
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
3
2
1
The formation of adenosine monophosphate (AMP) by condensation
of adenosine and phosphoric acid. The three linked units form the
nucleotide building block required for nucleic acid synthesis.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18-6 Drawing Nucleotides
Draw the structure of uridine monophosphate (UMP).
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Structure of Nucleic Acids
 A nucleic acid polymer contains nucleotide chains
in which the phosphate group of one nucleotide
links to the sugar ring of a second.

The primary structure: the sequence of bases

ACGT in this example
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Secondary Structure of DNA
 Elucidated by Watson and Crick in 1953
with data taken by Rosalind Franklin.
(Died before the Nobel was awarded)
 DNA consists of two strands of sugarphosphate backbones wound one
around the other in a double helix.
 The two helices are connected by
hydrogen bonds between bases that
pair within the molecule.
 Complimentary base pairs – the
matching of bases


Adenine pairs with thymine
Guanine pairs with cytosine
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
H
N
H
N
H
N
O
N
A
N
H
N
H
C
O
N
N
H
N
H N T
O
N
N
G
N
N
Is this going to happen?
N H
H
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
H
O
H
N
A
H
O
N
N
N
H
N
N
Or this?
H N T
O
Hydrogen bonding!
N
H
O
N
G
N
N
N
H
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
H
H
N
O
N
C
N
H
H
Structure of DNA
(a) A ball-and –stick
model, with the
sugar-phosphate
backbone colored
blue and the bases
colored red. (b) A
space-filling model,
showing C atoms in
blue, N atoms in dark
blue, H atoms in
white, O atoms in
red, and P atoms in
yellow.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Structure of RNA
 Similar to DNA, but…
 Sugar is ribose (not deoxyribose)
 RNA uses uracil instead of thymine
 RNA is much smaller
 RNA is usually single-stranded, not double-stranded.
 Complimentary base pairing (G-C and A-U) creates
loops and kinks
 The principle job of RNA is to provide information to
synthesize proteins.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
The structure of an RNA
molecule. Notice the
folding caused by the
intrastrand base paring.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.7 Proteins
Learning objective:
Explain primary, secondary, and tertiary structures of
proteins
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
18.7 Proteins
 The most important biochemicals in cells are proteins
(enzymes, antibodies, hormones, transport molecules,
and structural materials)
Protect organisms from disease
 Extract energy from food
 Move essential cellular components
 Responsible for vision, taste and smell
 And many other tasks

 Proteins are the molecular machinery of the cell.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
 All proteins are
polyamides.
 Amino acids make
up proteins.
 All amino acids in
proteins have a
central carbon
bonded to one
hydrogen and to a
side chain group, R
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Of the 20 amino acids, 11 have side chains containing polar groups (in yellow), and 9
have nonpolar side chains. One, proline, has a unique ring structure.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Polypeptides
• Amino acids condense to create an amide linkage.
• The amide group that contains the two amino acids is called a
peptide linkage.
• Protein synthesis occurs by sequential condensation at the
carboxylic end of the growing chain leading to a polypeptide.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
By convention, the terminal amino acid group is written on the left
and the terminal carboxylic acid group is written on the right.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 7 The Primary Structure of a Peptide
Draw the line structure of the peptide Asp-Met-Val-Tyr.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Primary Structure
of a Polypeptide
 The sequence of
amino acids is called
the primary structure.
 They are represented
using short-hand
notations for the
amino acids.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Secondary Structure
 Certain sections of a long polypeptide will fold into sheets or
twist into coils.
 The Helix
 Pleated Sheets
 These regions constitute the secondary structure.
 The 2° structure is determined by hydrogen bonding
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
2° Structure: The Helix
A helical secondary structure results from hydrogen bonding within
a single protein. The side chains are omitted to emphasize the
shape of the helix. Notice the hydrogen bonding between N-H and
C=O groups.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
2° Structure: The Pleated Sheet
The pleated sheet: the chains in a sheet are fully extended rather
than coiled, and hydrogen bonds exist between different portions of
the protein chains. The pleats are caused by the bond angles of the
peptide linkages.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Tertiary Structure
 Each protein has a unique 3D shape called the tertiary
(3o) structure
 This results from the bends and folds the peptide chain
makes to achieve the lowest possible energy.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Example 18 – 8 Hydrogen Bonding in Proteins
Draw a line structure that shows the various ways in
which water molecules form hydrogen bonds with a
protein backbone.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Globular Proteins
 Carry most of the work done by cells
 Are compact, roughly spherical structures with folds
and grooves
Enzymes: globular proteins that speed up biochemical
reactions
 Hemoglobin, antibodies, and hormones

Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Fibrous Proteins
 Structural components of cells and tissue are made of
proteins that form fibres.
 The fibrous proteins are the cables, girders, bricks and
mortar of organisms.
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.
Chapter 18 Visual Summary
Chemistry, 2nd Canadian Edition ©2013 John Wiley & Sons Canada, Ltd.