1. 1 CHAPTER 11 An Introduction to Organic Chemistry

2. 2 ORGANIC CHEMISTRY

3. 3 Types of Organic Compounds organic compounds. Vast majority of over 20 million known compounds are based on C: organic compounds. Generally contain C and H + other elements (O, N, S, Cl, F, Br, I, P, etc.) Great variety of compounds

4. 4 Isomerism Isomers: compounds that have identical composition but different structures Isomers: compounds that have identical composition but different structures Two forms of isomerism Two forms of isomerism Constitutional (or structural) Constitutional (or structural) Stereoisomerism Stereoisomerism Constitutional Constitutional Same empirical formula but different atom-to- atom connections Same empirical formula but different atom-to- atom connections Stereoisomerism Stereoisomerism Same atom-to-atom connections but different arrangement in space. Same atom-to-atom connections but different arrangement in space.

5. 5 Structural Isomers

6. 6 Cis-2-butene Stereoisomers: Geometric Geometric isomers can occur when there is a C=C double bond. Trans-2-butene

7. 7 Optical isomers are molecules with non- superimposable mirror images. Optical isomers are molecules with non- superimposable mirror images. Such molecules are called CHIRAL Such molecules are called CHIRAL Pairs of chiral molecules are enantiomers. Pairs of chiral molecules are enantiomers. Chiral molecules in solution can rotate the plane of plane polarized light. Chiral molecules in solution can rotate the plane of plane polarized light. Stereoisomers: Optical

8. 8 Chiral Compounds—Polarized Light

9. 9 Stereoisomers Isomers Chirality generally occurs when a C atom has 4 different groups attached. Lactic acid

10. 10 Alkanes have the general formula C n H 2n+2 Alkanes have the general formula C n H 2n+2 CH 4 = methane CH 4 = methane C 2 H 6 = ethane C 2 H 6 = ethane C 3 H 8 = propane C 3 H 8 = propane C 4 H 10 = butane C 4 H 10 = butane C 5 H 12 = pentane C 5 H 12 = pentane Hydrocarbons

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12. 12 Alkanes are colorless gases, liquids, and solids Generally unreactive (but undergo combustion) Not polar (or low polarity) and so are not soluble in water. Hydrocarbons: Alkanes

13. 13 Chapter 11 Introduction to Organic Chemistry: Alkanes 10.3 Alkanes with Substituents

14. 14 Isomers of Butane Isomers have the same molecular formula. have different atom arrangements. of butane (C 4 H 10 ) are a straight chain and a branched chain.

15. 15 Alkyl groups Alkyl groups are alkanes that are missing one H. substituents attached to carbon chains. named with a –yl ending. H H C CH 3 methyl H H H H C C CH 3 CH 2 ethyl H H

16. 16 Naming Substituents In the IUPAC system, a carbon branch is named as an alkyl group. halogen atoms are named as halo. TABLE 10.6

17. 17 Alkanes with Substituents CH 3 CH 3 CH CH 3 methylpropane methyl groups CH 3 CH 3 CH 3 CH CH 2 CH CH 3 2,4-dimethylpentane

18. 18 Naming Alkanes Give the name of CH 3 CH 3  CH 3 ─CH─CH─CH 3 STEP 1 Name the longest continuous chain. CH 3 CH 3  CH 3 ─CH─CH─CH 3 butane

19. 19 Naming Alkanes Give the name of CH 3 CH 3  CH 3 ─CH─CH─CH 3 STEP 2 Number chain. CH 3 CH 3  CH 3 ─CH─CH─CH 3 1 2 3 4 STEP 3 Locate substituents and name. 2,3-dimethylbutane

20. 20 Learning Check Write the name of Cl CH 3  CH 3 ─CH 2 ─CH─CH─CH 3

21. 21 Solution STEP 1 Longest chain is pentane. STEP 2 Number chain from end nearest substituent. Cl CH 3  CH 3 ─CH 2 ─CH─CH─CH 3 5 4 3 2 1 STEP 3 Locate substituents and name alphabetically. 3-chloro-2-methylpentane

22. 22 Learning Check Give the IUPAC name for each of the following: A. CH 3 CH 3 | CH 3 ─CH─CH 2 ─CH─CH 3 B. Cl CH 3 | | CH 3 ─CH 2 ─CH─CH 2 ─C─CH 2 ─CH 3 | Cl

23. 23 Solution A. CH 3 CH 3 | CH 3 ─CH─CH 2 ─CH─CH 3 2,4-dimethylpentane 1 2 3 4 5 B. Cl CH 3 more substituents = C3 | | CH 3 ─CH 2 ─CH─CH 2 ─C─CH 2 ─CH 3 | Cl 7 6 5 4 3 2 1 3,5-dichloro-3-methylheptane

24. 24 Name the following The 6 7 8 longest A. Cl CH 2 ─CH 2 ─CH 3 chain | | CH 3 ─CH 2 ─CH─CH 2 ─C─CH 2 ─CH 3 | | Br Cl 1 2 3 4 5 2-bromo-3,5-dichloro-5-ethyloctane

25. 25 Learning Check Draw the condensed structural formula for 2-bromo-4-chlorobutane.

26. 26 Solution 2-bromo-4-chlorobutane STEP 1 Longest chain has 4 carbon atoms. C─C─C─C STEP 2 Number chain and add substituents. Br Alphabetically:  bromo- first than chloro- C ─ C ─ C ─ C ─ Cl 1 2 3 4 STEP 3 Add hydrogen to complete 4 bonds to each C. Br  CH 3 ─CH─CH 2 ─CH 2 ─Cl WRONG name! It is 3-bromo-1-chlorobutane

27. 27 Naming Cycloalkanes with Substituents The name of a substituent is placed in front of the cycloalkane name. methylcyclobutane CH 3 chlorocyclopentane Cl

28. 28 Learning Check Name each of the following. 1. CH 3 CH 2 ─CH 3 2.

29. 29 Solution Name each of the following. 1. methylcyclopropane 2. ethylcyclohexane

30. 30 Chapter 11 Unsaturated Hydrocarbons 11.1 Alkenes and Alkynes

31. 31 Saturated hydrocarbons have the maximum number of hydrogen atoms attached to each carbon atom. are alkanes and cycloalkanes with single C-C bonds. CH 3 —CH 2 —CH 3 cyclohexane The cycle is considered as one unsaturation Saturated Hydrocarbons

32. 32 Unsaturated hydrocarbons have fewer hydrogen atoms attached to the carbon chain than alkanes. are alkenes with double bonds. are alkynes with triple bonds. Unsaturated Hydrocarbons

33. 33 Bond Angles in Alkenes and Alkynes According to VSEPR theory: the three groups bonded to carbon atoms in a double bond are at 120° angles. alkenes are flat because the atoms in a double bond all lie in the same plane. the two groups bonded to each carbon in a triple bond are at 180° angles.

34. 34 Naming Alkenes The names of alkenes C n H 2n use the corresponding alkane name. change the ending to –ene. AlkeneIUPACCommon H 2 C=CH 2 ethene ethylene H 2 C=CH─CH 3 propene propylene cyclohexene

35. 35 Ethene (Ethylene ) Ethene or ethylene is an alkene with the formula C 2 H 4. C n H 2n has two carbon atoms connected by a double bond. has two H atoms bonded to each C atom. is flat with all the C and H atoms in the same plane. is used to accelerate the ripening of fruits.

36. 36 Naming Alkynes The names of alkynes C n H 2n-2 use the corresponding alkane name. change the ending to –yne. AlkyneIUPACCommon HC ≡ CHethyne acetylene HC ≡ C─CH 3 propyne

37. 37 Naming Alkenes and Alkynes When the carbon chain of an alkene or alkyne has four or more C atoms, number the chain to give the lowest number to the first carbon in the double or triple bond. CH 2 =CH─CH 2 ─CH 3 1-butene 1 2 3 4 CH 3 ─CH=CH─CH 3 2-butene 1 2 3 4 CH 3 ─CH 2 ─C  C─CH 3 2-pentyne 5 4 3 2 1

38. 38 Learning Check Write the IUPAC name for each of the following: 1. CH 2 =CH─CH 2 ─CH 3 2. CH 3 ─CH=CH─CH 3 CH 3 | 3. CH 3 ─CH=C─CH 3 2-methyl-2-butene 4. CH 3 ─C  C─CH 3

39. 39 Solution Write the IUPAC name for each of the following: 1. CH 2 =CH─CH 2 ─CH 3 1-butene 2. CH 3 ─CH=CH─CH 3 2-butene CH 3 | 3. CH 3 ─CH=C─CH 3 2-methyl-2-butene 4. CH 3 ─C  C─CH 3 2-butyne

40. 40 Learning Check Write the IUPAC name for each of the following: A. CH 3 ─CH 2 ─C ≡ C─CH 3 CH 3  B. CH 3 ─CH 2 ─C=CH─CH 3

41. 41 Solution Write the IUPAC name for each of the following: A. CH 3 ─CH 2 ─C ≡ C─CH 3 2-pentyne CH 3  B. CH 3 ─CH 2 ─C=CH─CH 3 3-methyl-2-pentene

42. 42 Cis and Trans Isomers In an alkene the double bond, is rigid. holds attached groups in fixed positions. makes cis/trans isomers possible. CH 3 CH 3 CH 3 H C = C C = C H H H CH 3 cis trans

43. 43 In cis-trans isomers there is no rotation around the double bond in alkenes. groups attached to the double bond are fixed relative to each other. You can make a “double bond” with your fingers with both thumbs on the same side or opposite from each other. Cis-Trans Isomers

44. 44 Two isomers are possible when groups are attached to the double bond are different. In a cis isomer, groups are attached on the same side of the double bond. In the trans isomer, the groups are attached on opposite sides. Cis-Trans Isomers

45. 45 Cis-Trans Isomerism Alkenes cannot have cis-trans isomers if a carbon atom in the double bond is attached to identical groups. Identical 2-bromopropene 1,1-dibromoethene (not cis or trans) (not cis or trans) H H H Br

46. 46 Cis-Trans Isomers in Nature Insects emit tiny quantities of pheromones, which are chemicals that send messages. The silkworm moth attracts other moths by emitting bombykol, which has one cis and one trans double bond.

47. 47 Naming Cis-Trans Isomers The prefixes cis or trans are placed in front of the alkene name when there are cis-trans isomers. cis cis-1,2-dibromoethene trans-1,2-dibromoethene

48. 48 Learning Check Name each, using cis-trans prefixes when needed.

49. 49 Solution cis-1,2-dibromoethene trans-2-butene 1,1-dichloropropene

50. 50 Alkenes: Compounds with C=C Double Bonds How many isomers are possible for a compound with the formula C 4 H 8 ? How many isomers are possible for a compound with the formula C 4 H 8 ?