H

1. Alkenes, Reactions

2. Reactions, alkenes:
1. Addition of hydrogen (reduction).
2. Addition of halogens.
3. Addition of hydrogen halides.
4. Addition of water (hydration).
5. Polymerization

3. Reactions of Alkenes
C C
OH
H
Alcohol
H
H
OH
HO
1,2-Diol
O
C
O
X
H
X
X
OH
X
Alkane
Carbonyl Compound
Cyclopropane
Epoxide
1,2-Dihalide
Halide
Halohydrin
alkene

4. 1. Addition of hydrogen (reduction).
| | | |
— C = C — + H2 + Ni, Pt, or Pd  — C — C —
| |
H H
a) Requires catalyst.
b) #1 synthesis of alkanes
CH3CH=CHCH3 + H2, Ni  CH3CH2CH2CH3
2-butene n-butane

5. 2) Addition of halogens.
| | | |
— C = C — + X2  — C — C —
| |
X X
a) X2 = Br2 or Cl2
b) test for unsaturation with Br2
CH3CH2CH=CH2 + Br2  CH3CH2CHCH2
Br Br
1-butene 1,2-dibromobutane

6. 3. Addition of hydrogen halides.
| | | |
— C = C — + HX  — C — C —
| |
H X
a) HX = HI, HBr, HCl
CH3CH=CH2 + HI  CH3CHCH3
I
CH3 CH3
CH3C=CH2 + HBr  CH3CCH3
Br

7. CH3CH2CH=CH2 + HCl  CH3CH2CHCH3
Cl
CH3 CH3
CH3CH=CCH3 + HBr  CH3CH2CCH3
Br
CH3CH=CHCH3 + HI  CH3CH2CHCH3
I

8. 4. Addition of water.
| | | |
— C = C — + H2O, H+  — C — C —
| |
H OH
a) requires acid
CH3CH2CH=CH2 + H2O, H+  CH3CH2CHCH3
OH

9. 12. Polymerization.
CH2=CH2 + heat, pressure  -(CH2CH2)-n n = 10,000+
polyethylene
CH3CH=CH2 polymerization  -(CH2CH)-n
CH3
polypropylene
CH2=CHCl poly…  -(CH2CH)-n
Cl
polyvinyl chloride (PVC)

10. Plastics: man-made polymers that at some time in their
manufacture are soft and pliable.
Thermoplastics: plastics that soften when heated.
Free radical polymerization.
| | | | | |
R• + — C = C —  R — C — C • + — C = C — 
| |

11. 2.2 IUPAC Nomenclature
Alkynes
of

12. Introduction
• Alkynes contain a triple bond.
• General formula is CnH2n-2
• Two elements of unsaturation for each triple
bond.
• Some reactions are like alkenes: addition
and oxidation.
• Some reactions are specific to alkynes.
=>

13. I. Comparing Hydrocarbons
(Unsaturated Compounds)
Alkanes contain single bonds only -ANE ending
CnH2n+2 (saturated)
Alkenes contain a double bond -ENE ending
CnH2n (unsaturated)
Alkynes contain a triple bond between -YNE ending
CnH2n-2 (unsaturated)

14. Nomenclature: IUPAC
• Find the longest chain containing the triple
bond.
• Change -ane ending to -yne.
• Number the chain, starting at the end closest
to the triple bond.
• Give branches or other substituents a
number to locate their position.
=>

15. CH C CH2 CH3
1-butyne
CH3CCCH3 2-butyne
CH3CH2CCCH3 2-Pentyne

16. c) 5-ethyl-4-methyl-2-heptyne
CH CH CH2
CH2 CH3
C
C
CH3
CH3
CH3

17. Name these:
CH3 CH
CH3
CH2 C C CH
CH3
CH3
CH3 C C CH2 CH2 Br
CH3 C CH
propyne
5-bromo-2-pentyne
2,6-dimethyl-3-heptyne =>

18. Common Names
Named as substituted acetylene.
CH3 C CH
methylacetylene
CH3CH2CCCH3 2-pentyne
ethylmethylacetylene
C3H4 CH3CCH methylacetylene
propyne

19. Physical Properties of Alkynes
• Nonpolar, insoluble in water.
• Soluble in most organic solvents.
• Boiling points similar to alkane of same size.
• Less dense than water.
• Up to 4 carbons, gas at room temperature.
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20. Preparation of Alkynes by Double Elimination
2.3
Alkynes are prepared from dihaloalkanes by elimination.