2.7 Physical Properties of Alkenes

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 Combustion 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. The double bond becomes a single bond.

7. Symmetrical Addition Reactions: In which identical atoms are added to each carbon of the double bond. • 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 Cl2 or Br2 to C=C

9. catalyst = Pt, Pd, Ni HYDROGENATION Hydrogenation is the addition of hydrogen (H2) to a functional group. It requires a catalyst (cat) NO REACTION WITH C=C IN AROMATIC RINGS!

10. HALOGENATIONAddition of Cl2 and Br2 to alkenes: • Alkenes react with the halogens Br2 and Cl2 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. Br2

12. 2. UnSymmetrical addition reactions HYDROHALOGENATION : The addition of H-Cl, H-Br or H-I to C=C Hydration: The addition of H2O 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 H2SO4. Markovnikov’s rule applies.