12.1-Alkenes-and-Alkynes.ppt chemistry 1

Chemical,

1. 1
Chapter 12 Unsaturated
Hydrocarbons
12.1
Alkenes and Alkynes
General, Organic, and Biological Chemistry

2. 2
Unsaturated hydrocarbons
have fewer hydrogen atoms
attached to the carbon chain
than do alkanes
are alkenes with double C=C
bonds
are alkynes with triple C≡C
bonds
Unsaturated Hydrocarbons
General, Organic, and Biological Chemistry

3. 3
Bond Angles in Alkenes
According to VSEPR
theory:
Three groups in a
double bond are bonded
at 120° angles.
Alkenes are flat because
the atoms in a double
bond lie in the same
plane.
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

4. 4
Bond Angles in Alkynes
According to VSEPR theory:
The atoms in a triple bond have a 180° angle.
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

5. 5
Naming Alkenes
The names of alkenes
use the corresponding alkane name
change the ending from -ane to -ene
Alkene IUPAC Common
H
2
C=CH
2
Ethene Ethylene
H
2C=CH─CH
3Propene Propylene
Cyclohexene
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

6. Try these….
1.
2.
3.
4.
6

7. 7
Ethene (Ethylene)
Ethene, or ethylene,
is the alkene C
2
H
4
has two carbon atoms
connected by a double bond
has two H atoms bonded to
each C atom
is flat with all the C and H
atoms in the same plane
is used to accelerate the
ripening of fruits
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

8. 8
Naming Alkynes
The names of alkynes
use the corresponding alkane name
change the ending from -ane to -yne
Alkyne IUPAC Common
HC≡CH Ethyne Acetylene
HC≡C─CH
3
Propyne
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

9. 9
Guide to Naming Alkenes and
Alkynes
General, Organic, and Biological Chemistry

10. 10
Example of Naming Alkenes
Write the IUPAC name for CH
2═CH─CH
2─CH
3 and
CH
3
─CH≡CH─CH
3
.
STEP 1 Name the longest carbon chain with a double of triple bond:
butene, butyne
STEP 2 Number the chain from the end nearer the
double or triple bond:
CH
2═CH─CH
2─CH
3
1 2 3 4
CH
3
─CH≡CH─CH
3
1 2 3 4
STEP 3 Give the location and name of the double or
triple bond.
1-butene 2-butyne

General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

11. Names for Alkanes, Alkenes, and
Alkynes
11General, Organic, and Biological Chemistry

12. 12
Examples of Naming Alkenes with
Substituents
Write the IUPAC name for CH
3
│
CH
3─CH─CH=CH─CH
3
STEP 1 Name the longest carbon chain: pentene
STEP 2 Number the chain from the end nearer the
double or triple bond:
CH
3
│
CH
3─CH─CH=CH─CH
3
5 4 3 2 1
STEP 3 Give the location and name of the substituent
and double or triple bond:
4-methyl-2-pentene
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

13. 13
Naming Alkynes with Substituents
CH
3
│
Write the IUPAC name for HC≡C─CH─CH
3.
STEP 1 Name the longest carbon chain: butyne
STEP 2 Number the chain from the triple bond:
CH
3
│
HC≡C─CH─CH
3
1 2 3 4
STEP 3 Give the location and name of the substituent
and double or triple bond:
3-Methyl-1-butyne
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

14. 14

15. 15

16. 16
Learning Check
Write the IUPAC name for each of the following:
1) CH
2
═CH─CH
2
─CH
3
2) CH
3─CH═CH─CH
3
CH
3
|
3) CH
3─CH═C─CH
3
CH
3
|
4) CH
3
─C≡C─CH─CH
3
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

17. 17
Solution
Write the IUPAC name for each of the following:
1) CH
2
═CH─CH
2
─CH
3
1-butene
2) CH
3
─CH═CH─CH
3
2-butene
CH
3
|
3) CH
3
─CH═C─CH
3
2-methyl-2-butene
CH
3
|
4) CH
3
─C≡C─CH─CH
3
4-methyl-2-pentyne
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

18. 18
Learning Check
Draw the condensed structural formula for each of the
following:
A. 2-Hexyne
B. 3-Methyl-3-hexene
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

19. 19
Solution
Draw the condensed structural formula for each of the
following:
A. CH
3─C≡C─CH
2─CH
2─CH
3 2-hexyne
CH
3

B. CH
3─CH
2─C═CH─CH
2─CH
3 3-methyl-3-hexene
General, Organic, and Biological Chemistry Copyright
 © 2010 Pearson Education, Inc.

20. 20