Chapter 10 Organic Chemistry Copyright McGraw-Hill 2009 1

Chapter 10

Organic Chemistry

Copyright McGraw-Hill 2009 1


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.


Examples of Single and Multiple Bonds


Carbon’s lack of d electrons enhances stability


Examples of catenation


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

Copyright McGraw-Hill 20097


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.


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


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



Examples of functional groups


Examples of alcohols


Electrostatic maps of selected functional groups


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.


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.


Aldehydes

• Identify the longest chain that includes the carbonyl group.

• Change the –e ending to -al.• Number starting with the carbonyl (C=O)

carbon.



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.



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.


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.


CH3CH2

CH2C

CH3

O

CH3CH

CH2C

OH

OCH3

Name the following compounds.


CH3CH2

CH2C

CH3

O

2-pentanone

CH3CH

CH2C

OH

OCH3

3-methylbutanoic acid


Identify the functional groups in the following compound.

OC

CH3

O

NH2

COHO


OC

CH3

O

NH2

COHO

carboxylic acid

esteramine


• 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


• 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




Write the molecular formula and a structural formula for the following.

O


O

CH3COCH2CH3

C4H8O


O3

OOO

OO O

Draw the resonance structures for ozone.


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



• Geometrical isomers occur in compounds

that have restricted rotation around a bond.– cis (same side)– trans (opposite side)


• 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.



Bond designations to indicate stereochemistry


Measurement of Optical Activity

Dextrorotatory – plane of polarization is rotated to the right.

Levorotatory – plane of polarization is rotated to the left.


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


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


• Example: electrophilic addition


Text Figure 1038



• Example: nucleophilic addition


Comparison of electrophilic and nucleophilic addition


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


Electrophilic Substitution Reaction



Nucleophilic Substitution Reaction


Comparison of electrophillic and nucleophillic substitution


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


• Examples– Elimination

– Oxidation-reduction


– Isomerization


Draw the mechanism for the nucleophilic addition of CN to CH3CHO.


Draw the mechanism for the nucleophilic addition of CN to CH3CHO.

H3C C H

O

C N+ H3C C H

O

C

N


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


• Addition polymerization



• Condensation polymerization


• Ester and Ether Formation by Condensation


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)


• 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.




• Carbohydrates with different linkages

linkage

linkage


• Structure of a nucleotide (found in DNA)



• Unique features of carbon• Classes of organic compounds• Naming organic compounds• Isomerism

– Constitutional isomerism– Stereoisomerism

• Geometrical isomers• Optical isomers

Key Points


• Organic reactions– Addition reactions

• Electrophilic addition• Nucleophilic addition

– Substitution reactions• Electrophilic substitution• Nucleophilic substitution

– Elimination reactions– Oxidation-reduction reactions– Isomerization reactions

Key Points


• Polymers

– Addition

– Condensation

– Biological

• Proteins

• Carbohydrates

• Nucleic Acids

Key Points

Documents

Chapter 10 Organic Chemistry Copyright McGraw-Hill 2009 1