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Chapter 10
Organic Chemistry
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10.1 Why Carbon Is Different
• Electron configuration: [He]2s22p2
effectively prohibits ion formation
• Small atomic radius gives rise to short,
strong CC bonds and stable compounds
• Hybridized atoms (sp- and sp2-) can form
strong p bonds with unhybridzed p orbitals
• Catenation to form chains and rings
containing single, double and triple bonds.
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Examples of Single and Multiple Bonds
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Carbon’s lack of d electrons enhances stability
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Examples of catenation
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10.2 Classes of Organic Compounds
The seemingly limitless variety of organic
compounds results from:
• Carbon’s ability to form chains by bonding to
itself
• Presence of elements other than carbon and
hydrogen
• Functional groups – a group of atoms that
determines many of a molecule’s properties
• Multiple bonds
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How are Organic Compounds Named?
Alkanes
• Identify the longest continuous carbon
chain to get the parent name.
• Number the carbons in the continuous
chain, beginning at the end closest to the
substituent.
• Identify the substituent and use a number
and a prefix to specify location and
identity, respectively.
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Name the compound shown below.
H
H C H
H H
H H H
H C C C C C C H
H H
H H H
H C H
H
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H
H C H
H H
H H H
H C C C C C C H
H H
H H H
H C H
H
3,3-dimethylhexane
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Examples of functional groups
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Examples of alcohols
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Electrostatic maps of selected functional groups
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Naming Specific Functional Groups
Alcohols
• Identify the longest chain that includes the
–OH group.
• Change the –e ending to -ol.
• Number to give the –OH the lowest
number.
• When the chain also contains an alkyl
substituent, give the –OH the lowest
number.
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Carboxylic Acids
• Identify the longest chain that includes the
carboxyl group.
• Change the –e ending to –oic acid.
• Number starting with the carbonyl (C=O)
carbon.
• Use numbers and prefixes to indicate the
position and identity of any substituents.
Esters
• Name as derivatives of carboxylic acids by
replacing the –ic acid ending with -oate.
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Aldehydes
• Identify the longest chain that includes the
carbonyl group.
• Change the –e ending to -al.
• Number starting with the carbonyl (C=O)
carbon.
• Use numbers and prefixes to indicate the
position and identity of any substituents.
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Ketones
• Identify the longest chain that includes the
carbonyl group.
• Change the –e ending to -one.
• Number to give the carbonyl group the
lowest possible number.
• Use numbers and prefixes to indicate the
position and identity of any substituents.
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Primary Amines
• Identify the longest chain that includes the –
NH2 group.
• Change the –e ending to -amine.
• Number starting with the carbon to which the
–NH2 group is bonded.
• Use numbers and prefixes to indicate the
position and identity of any substituents.
Primary Amides
• Can be named as derivatives of carboxylic
acids.
• Or, by replacing the –e ending with –amide.
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Compounds with More Than
One Substituent
• Prefixes of di, tri, tetra, penta and so forth
are used to denote the number of
substituents.
• Substituent names are alphabetized.
• Numbers are used to indicate position of
the alphabetized substituents.
• Prefixes are not used in alphabetization.
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Name the following compounds.
O
CH3
CH3
CH2
CH2
CH3
O
CH
C
CH2
C
CH3
OH
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O
CH3
CH2
CH2
C
CH3
2-pentanone
CH3
CH3
O
CH
C
CH2
OH
3-methylbutanoic acid
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Identify the functional groups in the
following compound.
NH2
O
C
CH3
O
O
C
OH
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ester
O
CH3
C
amine
NH2
O
O
C
OH
carboxylic acid
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10.3 Representing Organic Molecules
• Condensed structural formula (Condensed
Structure): shows the same information as a
structural formula but in condensed form.
CH3(CH2)6CH3
• Kekulé structures: similar to Lewis
structure but without showing lone pairs
H H
H C C O H
H H
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• Skeletal Structures:
– Consist of straight lines that represent carboncarbon bonds.
– Heteroatoms (atoms other than carbon or
hydrogen) are shown explicitly
NH2
• Resonance: repositioning of electrons
shown by curved arrows
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Write the molecular formula and a
structural formula for the following.
O
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O
CH3COCH2CH3
C 4H 8O
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Draw the resonance structures for
ozone.
O3
O
O
O
O
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O
O
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10.4 Isomerism
• Constitutional (structural) isomerism
occurs when the same atoms can be
connected in two or more different ways.
• Stereisomerism occurs when atoms are
bonded in identical ways but differ in the
orientation of those bonds in space.
– Geometrical Isomers
– Optical Isomers
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• Geometrical isomers occur in compounds
that have restricted rotation around a bond.
– cis (same side)
– trans (opposite side)
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• Optical Isomers are nonsuperimposable
mirror images of one another.
– Such molecules are termed chiral.
– A pair of such mirror-image molecules are
called enantiomers.
– An equimolar mixture of the enantiomers is
called a racemic mixture.
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Bond designations to indicate stereochemistry
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Measurement of Optical Activity
Dextrorotatory – plane of polarization is rotated to the right.
Levorotatory – plane of polarization is rotated to the left.
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10.5 Organic Reactions
Important terms
• Electrophile
– a species with a region of positive or partial
positive charge
– electron-poor
• Nucleophile
– a species with a region of negative or partial
negative charge
– electron-rich
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Addition Reactions
• Reaction involving the addition of a
molecule or an ion to another molecule
• Electrophilic addition – adding species is
an electrophile
• Nucleophilic addition – adding species is
a nucleophile
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• Example:
electrophilic addition
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Text Figure 1038
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• Example: nucleophilic addition
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Comparison of electrophilic and nucleophilic
addition
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Substitution Reactions
• Reaction when one group is replaced by
another.
• Electrophilic substitution – an
electrophile attacks an aromatic molecule
and replaces a hydrogen atom
• Nucleophilic substitution – a nucleophile
replaces another group on a carbon atom
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Electrophilic Substitution Reaction
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Nucleophilic Substitution Reaction
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Comparison of electrophillic and nucleophillic
substitution
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Other Types of Organic Reactions
• Elimination – reaction in which a double
bond forms and small molecule is
removed
• Oxidation-reduction – involve the loss
and gain of electrons
• Isomerization – one isomer is converted
to another
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• Examples
– Elimination
– Oxidation-reduction
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– Isomerization
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Draw the mechanism for the nucleophilic
addition of CN to CH3CHO.
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Draw the mechanism for the nucleophilic
addition of CN to CH3CHO.
O
H3C C H
O
+
C N
H3C C H
C
N
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10.6 Organic Polymers
• Polymers – molecular compounds made up
of many repeating units called monomers
• Types
– Addition polymers form when monomers
join end to end
– Condensation polymers form when two
different functional groups combine in an
elimination reaction
• Often are copolymers which are made
of two or more different monomers
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• Addition polymerization
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• Condensation polymerization
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• Ester and Ether Formation by Condensation
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Biological Polymers
Naturally occurring polymers include
• Proteins – polymers of amino acids
• Polysaccharides – polymers of sugars
• Nucleic acids – polymers of nucleotides
– DNA (deoxyribonucleic acid)
– RNA (ribonucleic acid)
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• Protein formation
− Peptide bonds are also called amide
linkages since they contain an amide
functional group.
− Very long chains are called proteins while
shorter chains are called polypeptides.
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• Carbohydrates with different linkages
b linkage
a linkage
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• Structure of a nucleotide (found in DNA)
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Key Points
•
•
•
•
Unique features of carbon
Classes of organic compounds
Naming organic compounds
Isomerism
– Constitutional isomerism
– Stereoisomerism
• Geometrical isomers
• Optical isomers
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Key Points
• Organic reactions
– Addition reactions
• Electrophilic addition
• Nucleophilic addition
– Substitution reactions
• Electrophilic substitution
• Nucleophilic substitution
– Elimination reactions
– Oxidation-reduction reactions
– Isomerization reactions
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Key Points
• Polymers
– Addition
– Condensation
– Biological
• Proteins
• Carbohydrates
• Nucleic Acids
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