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Transcript of Chapter 10 Organic Chemistry Copyright McGraw-Hill 2009 1.
Chapter 10
Organic Chemistry
Copyright McGraw-Hill 2009 1
Copyright McGraw-Hill 2009 2
10.1 Why Carbon Is Different
• Electron configuration: [He]2s22p2 effectively prohibits ion formation
• Small atomic radius gives rise to short, strong CC bonds and stable compounds
• Hybridized atoms (sp- and sp2-) can form strong 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.
C C
H
H
H
H
C
H
C
C
C
C
H
H
C
H
H
H
H
H
HH
H
HH
H
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3,3-dimethylhexane
C C
H
H
H
H
C
H
C
C
C
C
H
H
C
H
H
H
H
H
HH
H
HH
H
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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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CH3CH2
CH2C
CH3
O
CH3CH
CH2C
OH
OCH3
Name the following compounds.
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CH3CH2
CH2C
CH3
O
2-pentanone
CH3CH
CH2C
OH
OCH3
3-methylbutanoic acid
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Identify the functional groups in the following compound.
OC
CH3
O
NH2
COHO
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OC
CH3
O
NH2
COHO
carboxylic acid
esteramine
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• Condensed structural formula (Condensed Structure): shows the same information as a structural formula but in condensed form.
CH3(CH2)6CH3
• Kekule structures: similar to Lewis structure but without showing lone pairs
10.3 Representing Organic Molecules
C CH
H
H
O
H
H
H
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• Skeletal Structures: – Consist of straight lines that represent carbon-
carbon bonds.
– Heteroatoms (atoms other than carbon or
hydrogen) are shown explicitly
• Resonance: repositioning of electrons shown by curved arrows
NH2
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Write the molecular formula and a structural formula for the following.
O
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O
CH3COCH2CH3
C4H8O
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O3
OOO
OO O
Draw the resonance structures for ozone.
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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.
H3C C H
O
C N+ H3C C H
O
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
linkage
linkage
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• Structure of a nucleotide (found in DNA)
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• Unique features of carbon• Classes of organic compounds• Naming organic compounds• Isomerism
– Constitutional isomerism– Stereoisomerism
• Geometrical isomers• Optical isomers
Key Points
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• Organic reactions– Addition reactions
• Electrophilic addition• Nucleophilic addition
– Substitution reactions• Electrophilic substitution• Nucleophilic substitution
– Elimination reactions– Oxidation-reduction reactions– Isomerization reactions
Key Points
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• Polymers
– Addition
– Condensation
– Biological
• Proteins
• Carbohydrates
• Nucleic Acids
Key Points