Chapter 8 Alkenes and alkynes I. Properties and synthesis

1. Chapter 8 Alkenes and alkynes I.Properties and synthesis 8.1 Introduction Alkenes are hydrocarbons whose molecules contain the carbon-carbon double bond. Hydrocarbons whose molecules contain the carbon-carbon triple bond are called alkynes.

2. 8.2 Nomenclature of alkenes and cycloalkenes

3. The IUPAC rules for naming alkenes are similar in many respects to those for naming alkanes Selecting the longest chain that contains the double bond Number the chain

4. 3. Indicate the locations of the substituent groups

5. 4. Number substituted cycloalkenes in the way that gives the carbon atoms of the double bond the 1- and 2- positions and that also gives the substituent groups the lower numbers at the first point of difference

6. 5. Two frequently encountered alkenyl groups are the vinyl group and the allyl group.

7. 6. Designate the geometry of a double bond of a disubstituted alkene with the prefixes cis- and trans-

8. 8.2A The ( E )-( Z ) System for designation alkene diastereomers

10. 8.3 Nomenclature of alkynes 8.3A IUPAC Nomenclature Unbranched alkynes, for example, are named by replacing the –ane of the name of the corresponding alkane with the ending –yne. The chain is numbered in order to give the carbon atoms of the triple bond the lower possible numbers.

12. 8.4 Physical properties of alkenes and alkynes8.5 Hydrogenation of alkenes

13. 8.6 Hydrogenation: The function of the catalyst

14. Catalytic hydrogen and Syn--addition

15. 8.6A Syn and anti additions

16. 8.7A Syn addition of hydrogen: Synthesis of cis-alkenes

17. 8.7B Anti addition of hydrogen: Synthesis of trans-alkenes

18. 8.9 Relative stabilities of alkenes 8.9A Heats of hydrogenation

19. The order of stabilities;

20. 8.9B Relative stabilities from heats of combustion

21. 8.9C Overall relative stabilities of alkenes

22. 8.10 Cycloalkenes The rings of cycloalkenes containing five carbon atoms or fewer exist only in the cis form. Therefore, fewer exist in the trans form because of the ring strain.

23. Cis- and trans-Cycloalkenes

24. 8.11 Synthesis of alkenes via elimination reactions

25. 8.12 Dehydrohalogenation of alkyl halides

26. 8.12A E2 reactions: The orientation of the double bond in the product. Zaltsev’s Rule(查依采夫规则） 查依采夫规则----主要产物是双键连有烃基较多的。

28. 8.12C The stereochemistry of E2 reactions:

32. 8.13 Dehydration of alcohols • The experimental conditions----temperature • and acid concentration

33. Ease of Dehydration

34. 8.13A Mechanism of alcohol dehydration: An E1 reaction

36. Ease of dehydration for E1 reaction

37. 8.15 Carbocation stability and the occurrence of molecular rearrangements (正碳离子的稳定性和分子的重排的发生）

39. The type of rearrengement

40. Rearrengement mechanism (E1 reaction)

41. 8.16 Alkenes by debromination of vicinal dibromides

43. 8.17 Summary of methods for the preparation of alkenes

44. 2. Dehydration of alcohols

45. 3. Dehalogenation of vic-dibromides

46. 4. Hydrogenlation of alkynes

47. 8.18Synthesis of alkynes by elimination reaction

49. 8.19 The Acidity of terminal alkynes The hydrogen atoms of ethyne are considerably more acidic than those of ethene or ethane

50. Relative acidity;