1. 1 Chapter 12 Unsaturated Hydrocarbons 12.1 Alkenes and Alkynes

2. 2 Saturated hydrocarbons have the maximum number of hydrogen atoms attached to each carbon atom. are alkanes and cycloalkanes with single C-C bonds. CH 3 —CH 2 —CH 3 Saturated Hydrocarbons

3. 3 Unsaturated hydrocarbons have fewer hydrogen atoms attached to the carbon chain than alkanes. are alkenes with double bonds. are alkynes with triple bonds. Unsaturated Hydrocarbons

4. 4 Bond Angles in Alkenes and Alkynes According to VSEPR theory: the three groups bonded to carbon atoms in a double bond are at 120° angles. alkenes are flat because the atoms in a double bond all lie in the same plane. the two groups bonded to each carbon in a triple bond are at 180° angles.

5. 5 Naming Alkenes The names of alkenes use the corresponding alkane name. change the ending to –ene. AlkeneIUPACCommon H 2 C=CH 2 ethene ethylene H 2 C=CH─CH 3 propene propylene cyclohexene

6. 6 Ethene (Ethylene ) Ethene or ethylene is an alkene with the formula 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.

7. 7 Naming Alkynes The names of alkynes use the corresponding alkane name. change the ending to –yne. AlkyneIUPACCommon HC ≡ CHethyne acetylene HC ≡ C─CH 3 propyne

8. 8 Naming Alkenes and Alkynes When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH 2 =CH─CH 2 ─CH 3 1-butene 1 2 3 4 CH 3 ─CH=CH─CH 3 2-butene 1 2 3 4 CH 3 ─CH 2 ─C  C─CH 3 2-pentyne 5 4 3 2 1

9. 9 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 4. CH 3 ─C  C─CH 3

10. 10 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 4. CH 3 ─C  C─CH 3 2-butyne

11. 11 Learning Check Write the IUPAC name for each of the following: A. CH 3 ─CH 2 ─C ≡ C─CH 3 CH 3  B. CH 3 ─CH 2 ─C=CH─CH 3

12. 12 Solution Write the IUPAC name for each of the following: A. CH 3 ─CH 2 ─C ≡ C─CH 3 2-pentyne CH 3  B. CH 3 ─CH 2 ─C=CH─CH 3 3-methyl-2-pentene