1. © 2014 Pearson Education, Inc. Alkenes Structure, Nomenclature, and an introduction to Reactivity Thermodynamics and Kinetics Chapter 5 Paula Yurkanis Bruice University of California, Santa Barbara

2. © 2014 Pearson Education, Inc. Molecular Formula and the Degree of Unsaturation molecular formula = C n H 2n+2 – 2 hydrogens for every π bond or ring degree of unsaturation = the total numbers of π bonds and rings

3. © 2014 Pearson Education, Inc. Compounds with Molecular Formula = C 8 H 14 C n H 2n+2 = C 8 H 18 Therefore, C 8 H 14 has two degrees of unsaturation. compounds with six hydrogens and two degrees of unsaturation

4. © 2014 Pearson Education, Inc. Saturated and Unsaturated Hydrocarbons Saturated hydrocarbons have no double bonds. Unsaturated hydrocarbons have one or more double bonds.

5. © 2014 Pearson Education, Inc. Nomenclature of Alkenes Replace “ane” of alkane with “ene.” The functional group gets the lowest possible number.

6. © 2014 Pearson Education, Inc. Stereoisomers are Named Using a cis or trans Prefix

7. © 2014 Pearson Education, Inc. Nomenclature of Dienes two double bonds = diene

8. © 2014 Pearson Education, Inc. Number in the direction so that the functional group gets the lowest number. Nomenclature of Alkenes

9. © 2014 Pearson Education, Inc. Substituents are stated in alphabetical order. Nomenclature of Alkenes

10. © 2014 Pearson Education, Inc. Nomenclature of Alkenes

11. © 2014 Pearson Education, Inc. Nomenclature of Cyclic Alkenes A number is not needed to denote the position of the functional group; it is always between C1 and C2.

12. © 2014 Pearson Education, Inc. Nomenclature of Alkenes

13. © 2014 Pearson Education, Inc. Nomenclature of Alkenes

14. © 2014 Pearson Education, Inc. Vinylic and Allylic Carbons vinylic carbon: the sp 2 carbon of an alkene allylic carbon: a carbon adjacent to a vinylic carbon

15. © 2014 Pearson Education, Inc. Double Bonds Have Restricted Rotation Rotation about a double bond breaks the π bond.

16. © 2014 Pearson Education, Inc. Six Atoms of an Alkene are in the Same Plane

17. © 2014 Pearson Education, Inc. Alkenes Have Cis–Trans Isomers Cis: The hydrogens are on the same side of the ring. Trans: The hydrogens are on opposite sides of the ring. cistrans They have different configurations; they can be separated.

18. © 2014 Pearson Education, Inc. Which Is Cis and Which Is Trans?

19. © 2014 Pearson Education, Inc. The E,Z System of Nomenclature Z = Zusammen (together)E = Entgegen (opposite)

20. © 2014 Pearson Education, Inc. Relative Priorities The relative priorities of the two groups depends on the atomic numbers of the atoms attached to the sp 2 carbon.

21. © 2014 Pearson Education, Inc. The E and Z Isomers

22. © 2014 Pearson Education, Inc. E and Z

23. © 2014 Pearson Education, Inc. E and Z

24. © 2014 Pearson Education, Inc. Isomers for Compounds with Two Double Bonds

25. © 2014 Pearson Education, Inc. Reactions of Organic Compounds Organic compounds can be divided into families. All members of a family react in the same way. The family a compound belongs to depends on its functional group.

26. © 2014 Pearson Education, Inc. Electrophiles An electrophile has a positive charge, a partial positive charge, or an incomplete octet.

27. © 2014 Pearson Education, Inc. Nucleophiles A nucleophile has a negative charge or a lone pair.

28. © 2014 Pearson Education, Inc. A Nucleophile Reacts with an Electrophile Your first organic reaction is a two-step reaction.

29. © 2014 Pearson Education, Inc. Curved Arrows Curved arrows are used to show the mechanism of a reaction. The mechanism of a reaction is the step-by-step description of the process by which reactants are converted into products. first step of the reaction

30. © 2014 Pearson Education, Inc. second step of the reaction The curved arrow shows where the electrons start from and where they end up. Curved Arrows

31. © 2014 Pearson Education, Inc. How to Draw Curved Arrows

32. © 2014 Pearson Education, Inc. How to Draw Curved Arrows

33. © 2014 Pearson Education, Inc. How to Draw Curved Arrows

34. © 2014 Pearson Education, Inc. How to Draw Curved Arrows

35. © 2014 Pearson Education, Inc. Thermodynamics and Kinetics

36. © 2014 Pearson Education, Inc. A Reaction Coordinate Diagram A reaction coordinate diagram shows the energy changes that take place in each step of a reaction.

37. © 2014 Pearson Education, Inc. The Equilibrium Constant The equilibrium constant gives the concentration of reactants and products at equilibrium.

38. © 2014 Pearson Education, Inc. Exergonic and Endergonic Reactions

39. © 2014 Pearson Education, Inc. Gibbs Free-Energy Change (∆G°)

40. © 2014 Pearson Education, Inc. Calculating ∆H°

41. © 2014 Pearson Education, Inc.

42. Reaction Coordinate Diagrams for Fast and Slow Exergonic and Endergonic Reactions

43. © 2014 Pearson Education, Inc. Free Energy of Activation (∆G ‡ ) The free energy of activation is the energy barrier of the reaction.

44. © 2014 Pearson Education, Inc. Rate of a Reaction Increasing the concentration increases the rate. Increasing the temperature increases the rate. The rate can also be increased by a catalyst.

45. © 2014 Pearson Education, Inc. The Rate of a Reaction versus The Rate Constant for a Reaction

46. © 2014 Pearson Education, Inc. The Rate of a Reaction versus The Rate Constant for a Reaction

47. © 2014 Pearson Education, Inc. The Arrhenius Equation The value of A pertains to the frequency and orientation of collisions. e –E a /RT The term e –E a /RT provides the reaction of molecules with the needed activation energy at a given temperature (T).

48. © 2014 Pearson Education, Inc. An Electrophilic Addition Reaction Transition states have partially formed bonds.

49. © 2014 Pearson Education, Inc. Reaction Coordinate Diagram for Each Step of the Addition of HBr to 2-Butene

50. © 2014 Pearson Education, Inc. Reaction Coordinate Diagram for the Addition of HBr to 2-Butene The rate-limiting step of the reaction is the step that has its transition state at the highest point of the reaction coordinate diagram.

51. © 2014 Pearson Education, Inc. A Catalyst A catalyst provides a pathway for a reaction with a lower energy barrier. A catalyst does not change the energy of the starting point (the reactants) or the energy of the end point (the products).

52. © 2014 Pearson Education, Inc. Enzymes Most biological reactions require a catalyst. Most biological catalysts are proteins called enzymes. The reactant of a biological reaction is called a substrate.

53. © 2014 Pearson Education, Inc. The Active Site of an Enzyme An enzyme binds its substrate at its active site.

54. © 2014 Pearson Education, Inc. Enzyme Side Chains that Bind the Substrate Some enzyme side chains bind the substrate. Some enzyme side chains are acids, bases, and nucleophiles that catalyze the reaction.

55. © 2014 Pearson Education, Inc. Some enzyme side chains are acids, bases, and nucleophiles that catalyze the reaction. Enzyme Side Chains that Catalyze the Reaction