1. CHEM 2124 – General Chemistry II
Chapter 12 - Alkanes
CHEM 2124 – General Chemistry II
Alfred State College
Professor Bensley

2. Chapter 12 Learning Objectives
Identify and draw acyclic alkanes and cycloalkanes.
Identify constitutional isomers.
Name alkanes using the IUPAC system of nomenclature.
Predict the physical properties of alkanes.
Write equations for the complete and incomplete combustion of alkanes.

3. Chapter 12 – Alkanes I. Introduction What are alkanes?
What does the term saturated hydrocarbon mean?
What is a cycloalkane?

4. Chapter 12 – Alkanes II. Simple Alkanes
Methane is a one carbon alkane.
Ethane is a two carbon alkane.

5. Chapter 12 – Alkanes II. Simple Alkanes
Propane is a three-carbon alkane.
Are these both propane?

6. Chapter 12 – Alkanes II. Simple Alkanes
Butane is a four-carbon alkane.
Butane and isobutane are
isomers of each other.
What are Constitutional isomers ?

7. Chapter 12 – Alkanes II. Simple Alkanes
Pentane is a five-carbon alkane with three isomers:

9. III. Bond Rotation and Skeletal Structures
Chapter 12 – Alkanes
III. Bond Rotation and Skeletal Structures

10. IV. IUPAC Nomenclature (Alkanes)
Chapter 12 – Alkanes
IV. IUPAC Nomenclature (Alkanes)
What is it and why do we use IUPAC names?
The names of alkanes with substituents have three
parts.
Carbon substituents are called alkyl groups.

12. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
The longest chain may not be written horizontally
It does not matter if the chain is straight or has bends.
All three examples below have 6 C’s in their
longest chain:

13. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
Number the atoms in the carbon chain to
give the first substituent the lower number.
Step [2]
CORRECT
INCORRECT

14. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
Step [3]
Name and number the substituents.
Name the substituents as alkyl groups.
Use the numbers from step [2] to designate their
location.

15. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
Every carbon belongs to either the longest chain
or a substituent, but not both.
Each substituent needs its own number.
If two or more substituents are identical, use
prefixes to indicate how many.
# of Substituents
Prefix 2
di- 3
tri- 4
tetra-

16. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
The following compound contains two methyl
groups, so we use the name dimethyl for them.

17. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
Combine substituent names and numbers +
parent + suffix.
Step [4]
Alphabetize the substituents, ignoring prefixes.
Precede the name of each substituent by the
number that indicates its location.
There must be one number for each substituent.
Separate numbers by commas and separate
numbers from letters by dashes.

18. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
methyl at C2
CH3
CH3
CH3 CH
CH2
CH2
CH2
CH3 1 2
longest chain is 6 C’s = hexane
2-methylhexane

19. IUPAC Nomenclature (Alkanes)
HOW TO Name an Alkane Using the IUPAC System
methyl at C2
CH3
CH3
CH3 CH CH
CH2
CH2
CH3
CH3
CH3
methyl at C3 1 2 3
longest chain is 6 C’s = hexane
2,3-dimethylhexane

20. IUPAC Nomenclature (Alkanes)
Sample Problem
Give the IUPAC name for the following compound.
ethyl at C5
methyl at C2
CH3
CH3
CH3CH2
CH3CH2 H
CH3 C
CH2CH2 C C
CH2CH3 H H
CH3
CH3
methyl at C6 1 2 5 6
longest chain is 8 C’s = octane
5-ethyl-2,6-dimethyloctane

21. Chapter 12 – Alkanes
V. Cycloalkanes

22. Chapter 12 – Alkanes VI. Alkane Physical Properties Polarities
Phases of matter
Melting and Boiling
Solubility
Points
Density

23. Chapter 12 – Alkanes
VII. Applications of Alkanes

24. Chapter 12 – Alkanes
VIII. Alkane Reactions