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Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e Chapter 8 Alkenes: Structure and Preparation via Elimination.

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1 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. Klein, Organic Chemistry 2e Chapter 8 Alkenes: Structure and Preparation via Elimination Reactions Organic Chemistry Second Edition David Klein

2 8.1 Introduction to Elimination Elimination reactions often compete with substitution reactions. What are the two main ingredients for a substitution? – A nucleophile and an electrophile with a leaving group What are the two main ingredients for an elimination? – A base and an electrophile with a leaving group How is a base both similar and different from a nucleophile? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-2 Klein, Organic Chemistry 2e

3 8.1 Introduction to Elimination Consider – OH, which can act as a base or a nucleophile Attack at the α Carbon Reaction at the β Hydrogen β or 1,2 ALKENE Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-3 Klein, Organic Chemistry 2e

4 8.2 Alkenes Important alkenes Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-4 Klein, Organic Chemistry 2e

5 C=C double bonds are found in a variety of compounds including pheromones and many other classes of compounds 8.2 Alkenes Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-5 Klein, Organic Chemistry 2e

6 Why might it be helpful to know the chemical structure of pheromones such as those below? 8.2 Alkenes Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-6 Klein, Organic Chemistry 2e

7 Alkenes are also important compounds in the chemical industry 70 billion pounds of propylene (propene) and 200 billion pounds of ethylene (ethene) are both made from cracking petroleum each year 8.2 Alkenes Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-7 Klein, Organic Chemistry 2e

8 8.2 Alkenes Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-8 Klein, Organic Chemistry 2e

9 8.3 Alkene Nomenclature Alkenes are named using the same procedure we used in Chapter 4 to name alkanes with minor modifications 1.Identify the parent chain, which should include the C=C double bond 2.Identify and Name the substituents 3.Assign a locant (and prefix if necessary) to each substituent. Give the C=C double bond the lowest number possible 4.List the numbered substituents before the parent name in alphabetical order. Ignore prefixes (except iso) when ordering alphabetically 5.The C=C double bond locant is placed either just before the parent name or just before the -ene suffix Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-9 Klein, Organic Chemistry 2e

10 8.3 Alkene Nomenclature 1.Identify the parent chain, which should include the C=C double bond The name of the parent chain should end in -ene rather than –ane The parent chain should include the C=C double bond Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-10 Klein, Organic Chemistry 2e

11 8.3 Alkene Nomenclature 2.Identify and Name the substituents 3.Assign a locant (and prefix if necessary) to each substituent. Give the C=C double bond the lowest number possible – The locant is ONE number, NOT two. Although the double bond bridges carbons 2 and 3, the locant is the lower of those two numbers Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-11 Klein, Organic Chemistry 2e

12 8.3 Alkene Nomenclature 4.List the numbered substituents before the parent name in alphabetical order. Ignore prefixes (except iso) when ordering alphabetically 5.The C=C double bond locant is placed either just before the parent name or just before the -ene suffix Practice with SkillBuilder 8.1 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-12 Klein, Organic Chemistry 2e

13 8.3 Alkene Nomenclature Name the following molecule Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-13 Klein, Organic Chemistry 2e

14 8.4 Alkene Isomerism For the pi bond to remain intact, rotation around a double bond is prohibited As a result, cis and trans structures are not identical Is there a difference between cis-butane and trans- butane? What specific type of isomers are cis and trans butene? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-14 Klein, Organic Chemistry 2e

15 8.4 Alkene Isomerism In cyclic alkenes with less than 8 atoms in the ring, only cis alkenes are stable. WHY? Draw the structure for trans-cyclooctene When applied to bicycloakenes, this rule is called Bredt’s rule Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-15 Klein, Organic Chemistry 2e

16 8.4 Alkene Isomerism Apply Bredt’s rule to the compounds below The carbons of the C=C double bond and the atoms that are directly attached to them must be planar to maintain the pi bond overlap. A handheld model can be used to help visualize the p orbital overlap and resulting geometry Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-16 Klein, Organic Chemistry 2e

17 8.4 Alkene Isomerism Cis and trans modifiers are strictly used to describe C=C double bonds with identical groups on each carbon. Where are the identical groups in trans-2-pentene? For molecules with different groups attached to the C=C double bond, the E/Z notation is used instead of cis/trans notation Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-17 Klein, Organic Chemistry 2e

18 8.4 Alkene Isomerism Assigning E or Z to a stereoisomers 1.prioritize the groups attached to the C=C double bond based on atomic number Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-18 Klein, Organic Chemistry 2e

19 8.4 Alkene Isomerism Assigning E or Z to a stereoisomers 1.prioritize the groups attached to the C=C double bond based on atomic number 2.If the top priority groups are on the same side of the C=C double bond, it is Z (for zussamen, which means together) 3.If the top priority groups are on opposite sides of the C=C double bond, it is E (for entgegen, which means opposite) Practice with SkillBuilder 8.2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-19 Klein, Organic Chemistry 2e

20 8.5 Alkene Stability Because of steric strain, cis isomers are generally less stable than trans Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-20 Klein, Organic Chemistry 2e

21 8.5 Alkene Stability The difference in stability can be quantified by comparing the heats of combustion How does heat of combustion relate to stability? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-21 Klein, Organic Chemistry 2e

22 8.5 Alkene Stability Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-22 Klein, Organic Chemistry 2e

23 8.5 Alkene Stability Consider the following stability trend What pattern do you see? Practice with SkillBuilder 8.3 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-23 Klein, Organic Chemistry 2e

24 8.5 Alkene Stability List the following molecules in order of increasing heat of combustion – 2,3,4-trimethyl-1,3-pentadiene – 2-isopropyl-1,4-pentadiene – 3,3-dimethyl-1,5-hexadiene – 4,5-dimethylcyclohexene Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-24 Klein, Organic Chemistry 2e

25 8.6 Elimination Reactions in Detail In general, a H atom and a leaving group are eliminated To understand the mechanism of elimination, first recall the 4 mechanistic steps we learned in chapter 7 – Nucleophilic attack – Loss of a leaving group – Proton transfer – Rearrangement Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-25 Klein, Organic Chemistry 2e

26 8.6 Elimination Reactions in Detail The 4 mechanistic steps we learned in chapter 7 Which of the 4 steps MUST take place in every elimination mechanism? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-26 Klein, Organic Chemistry 2e

27 8.6 Elimination Reactions in Detail All elimination reactions involve both loss of a leaving group and proton transfer The mechanism may be a concerted (one step) process or a step-wise process. Which process is shown below? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-27 Klein, Organic Chemistry 2e

28 8.6 Elimination Reactions in Detail All elimination reactions involve both Loss of a leaving group and proton transfer The mechanism of the step-wise process: Could the steps happen in the reverse order? Practice with SkillBuilder 8.4 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-28 Klein, Organic Chemistry 2e

29 8.7 Elimination by E2 The E2 mechanism below matches the observed rate law. Write a reasonable rate law for the mechanism How will a change in [base] or [substrate] affect the reaction rate? What do the E and the 2 of the E2 notation represent? Practice with conceptual checkpoint 8.13 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-29 Klein, Organic Chemistry 2e

30 8.7 The Effect of Substrate on E2 The kinetics of E2 and S N 2 are quite similar. WHY? However, tertiary substrates are unreactive toward S N 2 while they react readily by E2. WHY? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-30 Klein, Organic Chemistry 2e

31 8.7 The Effect of Substrate on E2 3° substrates are more reactive toward E2 than are 1° substrates even though 1° substrates are less hindered The 3° substrate should proceed through a more stable transition state (kinetically favored) and a more stable product (thermodynamically favored). Let’s take a look at the energy diagram – see next slide Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-31 Klein, Organic Chemistry 2e

32 8.7 The Effect of Substrate on E2 How would both the transition state energy and the product energy be different if the substrate were 1°? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-32 Klein, Organic Chemistry 2e

33 Notice the differences in transition state and in product energies Practice with conceptual checkpoint 8.14 8.7 The Effect of Substrate on E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-33 Klein, Organic Chemistry 2e

34 If there are multiple reactive sites or regions on a molecule, multiple products are possible In elimination reactions, there are often different β sites that could be deprotonated to yield different alkenes 8.7 Regioselectivity of E2 What is the relationship between the alkene products? Regioselectivity occurs when one constitutional product is formed predominantly over the other Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-34 Klein, Organic Chemistry 2e Hofmann product Zaitsev product

35 The identity of the base can affect the regioselesctivity 8.7 Regioselectivity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-35 Klein, Organic Chemistry 2e

36 Why does the Zaitsev product predominate when a base that is NOT sterically hindered is used? Is the Zaitsev product kinetically favored, thermodynamically favored, or both? 8.7 Regioselectivity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-36 Klein, Organic Chemistry 2e

37 Why does a sterically hindered base favor the Hofmann product? Sterically hindered bases (sometimes called non- nucleophilic) are useful in many reactions Practice with SkillBuilder 8.5 8.7 Regioselectivity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-37 Klein, Organic Chemistry 2e

38 Consider the dehydrohalogenation (elimination of a hydrogen and a halogen) of 3-bromopentane 8.7 Stereoselectivity of E2 Why are both the transition state and product more stable for the trans product? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-38 Klein, Organic Chemistry 2e

39 What is the difference between stereoselective and stereospecific? Consider dehydrohalogenation for the molecule below 8.7 Stereospecificity of E2 There is only one available β Hydrogen to be eliminated You might imagine that it would be possible to form both the E and Z alkene products from this reaction. Draw both the E and the Z products Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-39 Klein, Organic Chemistry 2e

40 When the reaction is actually performed, only the E product is observed Is the E formed exclusively because it is formed through a slightly lower transition state? 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-40 Klein, Organic Chemistry 2e

41 To rationalize the stereospecificty of the reaction, consider the transition state for the reaction In the transition state, the C-H and C-Br bonds that are breaking must be rotated into the same plane as the pi bond that is forming Draw the transition state structure illustrating the coplanar geometry 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-41 Klein, Organic Chemistry 2e

42 There are two coplanar options for the molecule Why does the reaction proceed exclusively through the Anti coplanar structure? 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-42 Klein, Organic Chemistry 2e

43 To see the difference between Anti and Syn, Newman projections and hand held models can be helpful 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-43 Klein, Organic Chemistry 2e

44 Evidence suggests that a strict 180° angle is not necessary for E2 mechanisms. Similar angles (175–179°) are sufficient The term, anti-periplanar is generally used instead of anti-coplanar to account for slight deviations from coplanarity Although the E isomer is usually more stable because it is less sterically hindered, the requirement for an anti- periplanar transition state can often lead to the less stable Z isomer 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-44 Klein, Organic Chemistry 2e

45 Assuming they proceed through an anti-periplanar transition state, predict the products for the following reactions, and label them as cis or trans 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-45 Klein, Organic Chemistry 2e

46 Assuming they proceed through an anti-periplanar transition state, predict all of the products for the following reaction Will the reaction be stereospecific or stereoselective, and what factors most affect the product distribution? Practice with SkillBuilder 8.6 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-46 Klein, Organic Chemistry 2e

47 Consider the dehydrohalogenation of a cyclohexane Given the anti-periplanar requirement, which of the two possible chair conformations will allow for the elimination to occur? 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-47 Klein, Organic Chemistry 2e

48 Which of the two molecules below will NOT be able to undergo an E2 elimination reaction? WHY? It might be helpful to draw their chair structures and make a handheld model 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-48 Klein, Organic Chemistry 2e

49 Draw all of the possible products if each of the molecules below were to undergo dehydrohalogenation Practice with conceptual checkpoint 8.20 8.7 Stereospecificity of E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-49 Klein, Organic Chemistry 2e

50 Consider both regioselestivity and stereoselectivity to predict the products for the eliminations below, and draw complete mechanisms Practice with SkillBuilder 8.7 8.8 Predicting Products for E2 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-50 Klein, Organic Chemistry 2e

51 The E1 mechanism is a 2-step process Similar to S N 1 (chapter 7), the reaction rate for E1 is not affected by the concentration of the base What does the E and the 1 stand for in the E1 notation? 8.9 The E1 Mechanism Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-51 Klein, Organic Chemistry 2e

52 Given the rate law for E1, which step in the mechanism is the rate-determining slow step? If the second step were the slow step, how would you write the rate law? Practice with conceptual checkpoint 8.26 8.9 The E1 Mechanism Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-52 Klein, Organic Chemistry 2e

53 How does the substrate reactivity trend for E1 compare to the trend we discussed in chapter 7 for S N 1? WHY? Just like we did for S N 1 in chapter 7, to explain the reactivity trend above, we must compare the energy diagrams for each substrate 8.9 The Effect of Substrate on E1 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-53 Klein, Organic Chemistry 2e

54 To compare their energies, draw the structures for each transition state, intermediate, and product below 8.9 The Effect of Substrate on E1 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-54 Klein, Organic Chemistry 2e

55 Because E1 and S N 1 proceed by the same first step, their competition will generally result in a mixture of products How might you promote one reaction over the other? 8.9 The Effect of Substrate on E1 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-55 Klein, Organic Chemistry 2e

56 Alcohols can also undergo elimination or dehydration by E1, but the –OH group is not a stable leaving group 8.9 The Effect of Substrate on E1 In the E1 reaction below, once the water leaving group leaves the carbocation, what base should be used to complete the elimination? Practice with conceptual checkpoint 8.27 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-56 Klein, Organic Chemistry 2e

57 8.9 Regioselectivity for E1 The final step of the E1 mechanism determines the regioselectivity E1 reactions generally produce the Zaitsev product predominantly. WHY? Why can’t we control the regioselectivity in this reaction like we can in and E2 reaction? Practice with SkillBuilder 8.8 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-57 Klein, Organic Chemistry 2e

58 8.9 Stereoselectivity for E1 In the last step of the mechanism, a proton is removed from a β carbon adjacent to the sp 2 hybridized carbocation Draw the appropriate carbocation that forms in the reaction below, and rationalize the product distribution Practice with conceptual checkpoint 8.31 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-58 Klein, Organic Chemistry 2e

59 8.9 Stereoselectivity for E1 Considering stereochemistry and regiochemistry, predict the products if the molecule below was treated with concentrated sulfuric acid Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-59 Klein, Organic Chemistry 2e

60 8.10 Complete E1 Mechanisms Recall the similarities between S N 1 and E1 After the carbocation is formed and possibly rearranged, the E1 proton transfer neutralizes the charge Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-60 Klein, Organic Chemistry 2e

61 8.10 Complete E1 Mechanisms Why is the first proton transfer necessary? Practice with conceptual checkpoint 8.32 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-61 Klein, Organic Chemistry 2e

62 8.10 Complete E1 Mechanisms Explain why the carbocation rearranges Practice with conceptual checkpoint 8.33 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-62 Klein, Organic Chemistry 2e

63 8.10 Complete E1 Mechanisms The maximum number of steps in an E1 mechanism is generally four Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-63 Klein, Organic Chemistry 2e

64 8.10 Complete E1 Mechanisms Consider the energy diagram for the mechanism on the previous slide Assess each free energy change Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-64 Klein, Organic Chemistry 2e

65 8.10 Complete E1 Mechanisms The mechanism shows the formation of the major products Predict the minor elimination products as well Practice with SkillBuilder 8.9 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-65 Klein, Organic Chemistry 2e

66 8.11 Complete E2 Mechanisms In E2, the base removes the β proton as the LG leaves Will such a reaction require a relatively strong base? Will E2 dehydrations likely involve a proton transfer prior to the elimination? Practice with conceptual checkpoint 8.37 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-66 Klein, Organic Chemistry 2e

67 8.12 Substitution vs. Elimination Substitution and Elimination are always in competition Sometimes products are only observed from S or E Sometimes a mixture of products is observed Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-67 Klein, Organic Chemistry 2e

68 8.12 Substitution vs. Elimination To predict whether substitution or elimination will predominate, consider the factors below 1.Determine the function of the reagent. Is it more likely to act as a base, a nucleophile, or both? – Kinetics control nucleophilicity. WHY? HOW? – Thermodynamics control basicity. WHY? HOW? 2.Analyze the substrate and predict the expected mechanism (S N 1, S N 2, E1, or E2) 3.Consider relevant regiochemical and stereochemical requirements Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-68 Klein, Organic Chemistry 2e

69 8.12 Reagent Function: Nucleophilicy 1.Assessing the strength of a nucleophile The greater the negative charge, the more nucleophilic it is likely to be The more polarizable it is, the more nucleophilic it should be The less sterically hindered it is, the more nucleophilic it should be. WHY? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-69 Klein, Organic Chemistry 2e

70 8.12 Reagent Function: Basicity 1.Assessing the strength of a base Assess the strength of its conjugate acid quantitatively using the pK a of its conjugate acid Which is a stronger base Cl - or HSO 4 - ? As bases, are Cl - and HSO 4 - relatively strong or weak? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-70 Klein, Organic Chemistry 2e

71 8.12 Reagent Function: Basicity 1.Assessing the strength of a base If the base is neutral, assess the strength of its conjugate acid qualitatively using ARIO (atom, resonance, induction, orbital) – Compare CH 3 OH and CH 3 NH 2 If the base carries a negative formal charge, qualitatively assess the strength of the base using ARIO – Compare Cl - and HSO 4 - Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-71 Klein, Organic Chemistry 2e

72 8.12 Basicity vs. Nucleophilicity Consider each of the reagent categories Reagents that act as nucleophiles only are either highly polarizable and/or they have very strong conjugate acids Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-72 Klein, Organic Chemistry 2e

73 8.12 Basicity vs. Nucleophilicity Reagents that act as bases only have either very low polarizability and/or they are sterically hindered Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-73 Klein, Organic Chemistry 2e

74 8.12 Basicity vs. Nucleophilicity The stronger the reagent, the more likely it is to promote S N 2 or E2. WHY? The more sterically hindered reagents are more likely to promote elimination than substitution. WHY? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-74 Klein, Organic Chemistry 2e

75 The weaker the reagent, the more likely it is to promote S N 1 or E1. WHY? Practice with SkillBuilder 8.10 8.12 Basicity vs. Nucleophilicity Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-75 Klein, Organic Chemistry 2e

76 8.13 Predicting Subst. vs. Elim. 1.Analyze the function of the reagent (nucleophile and/ or base) 2.Analyze the substrate (1°, 2°, or 3°) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-76 Klein, Organic Chemistry 2e

77 8.13 Predicting Subst. vs. Elim. 1.Analyze the function of the reagent (nucleophile and/ or base) 2.Analyze the substrate (1°, 2°, or 3°) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-77 Klein, Organic Chemistry 2e

78 8.13 Predicting Subst. vs. Elim. 1.Analyze the function of the reagent (nucleophile and/ or base) 2.Analyze the substrate (1°, 2°, or 3°) Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-78 Klein, Organic Chemistry 2e

79 8.13 Predicting Subst. vs. Elim. 1.Analyze the function of the reagent (nucleophile and/ or base) 2.Analyze the substrate (1°, 2°, or 3°) Practice with SkillBuilder 8.11 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-79 Klein, Organic Chemistry 2e

80 8.14 Predicting Products 1.Analyze the function of the reagent (nucleophile and/ or base) 2.Analyze the substrate (1°, 2°, or 3°) 3.Consider regiochemistry and stereochemistry Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-80 Klein, Organic Chemistry 2e

81 8.14 Predicting Products 3.Consider regiochemistry and stereochemistry Practice with SkillBuilder 8.12 Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-81 Klein, Organic Chemistry 2e

82 Additional Practice Problems Name the following molecules Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-82 Klein, Organic Chemistry 2e

83 Additional Practice Problems Label the molecules below as either cis or trans and either E or Z where appropriate Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-83 Klein, Organic Chemistry 2e

84 Additional Practice Problems For the substrate, give both the kinetically favored E2 product and the thermodynamically favored E2 product. Explain what conditions can be used to favor each. Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-84 Klein, Organic Chemistry 2e

85 Additional Practice Problems Since tertiary substrates react more readily than secondary or primary in both E1 and E2 mechanisms, what factor(s) usually controls which mechanism will dominate and why? Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-85 Klein, Organic Chemistry 2e

86 Consider both regioselestivity and stereoselectivity to predict the major product for the elimination below Additional Practice Problems Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-86 Klein, Organic Chemistry 2e

87 Predict the major product if the alcohol below were treated with concentrated sulfuric acid. Be aware of the possible rearrangements. Additional Practice Problems Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-87 Klein, Organic Chemistry 2e

88 Predict the major product for the following reactions considering competing substitution and elimination pathways. Additional Practice Problems Copyright © 2015 John Wiley & Sons, Inc. All rights reserved. 8-88 Klein, Organic Chemistry 2e


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