1 2.7 Physical Properties of Alkenes

2 Nonpolar Insoluble in water Soluble in nonpolar organic solvents. Less dense than water: they float on water. PHYSICAL PROPERTIES LIKE ALKANES

3 2.8 Chemical Properties of Alkenes

4 REACTIONS OF ALKENES CCombustion AAddition reactions : hydrogenation halogenation hydrohalogenation hydration (addition of water)

5 Addition reactions: A substance adds to the multiple bond of an unsaturated reactant to yield a saturated product that has only single bonds.

6 In an addition reaction the atoms of the reactant molecule attach to the carbon atoms originally joined by a double bond. Th e double bond becomes a single bond.

7 1.Symmetrical Addition Reactions: In which identical atoms are added to each carbon of the double bond. 2.Unsymmetrical Addition Reactions: In which different groups are added to each carbon of the double bond. For example, hydration or hydrohalogenation.

8 1. Symmetrical addition reactions HYDROGENATION: The addition of H-H to C=C HALOGENATION: The addition of Cl 2 or Br 2 to C=C

9 Hydrogenation is the addition of hydrogen (H 2 ) to a functional group. It requires a catalyst (cat) HYDROGENATION catalyst = Pt, Pd, Ni NO REACTION WITH C=C IN AROMATIC RINGS!

10 HALOGENATION Addition of Cl 2 and Br 2 to alkenes: Alkenes react with the halogens Br 2 and Cl 2 to give the 1,2-dihaloalkanes. D:\Chem 11\movies\addition.mov

11 Bromine in water is a reddish brown solution. Bromine adds to the alkene to form colorless dibromo compounds. Br 2

12 2. UnSymmetrical addition reactions HYDROHALOGENATION : The addition of H-Cl, H- Br or H-I to C=C Hydration: The addition of H 2 O to C=C

13 HYDROHALOGENATION Addition of HCl and HBr to alkenes: Alkenes react with hydrogen bromide and hydrogen chloride to give alkyl bromide or alkyl chloride products.

14 Markovnikov rule: In the addition of HX to an alkene, the H becomes attached to the carbon that already has the more H’s, and X becomes attached to the carbon that has fewer H’s. D:\Chem 11\movies\HCLadddition.mov

15 HYDRATION Addition of water (H-OH) to alkenes An alcohol is produced on treatment of the alkene with water in the presence of a strong acid catalyst, such as H 2 SO 4. Markovnikov’s rule applies.

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