10-23 - 10/24/2009 The major product of the following...

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Unformatted text preview: 10/24/2009 The major product of the following reaction is 2-butene because of electronic not steric effects. The major product of the following reaction is 2-butene because of electronic effects. least hindered H atom A. A. Very sure this is true B. B. Somewhat sure this is true C. Maybe this is true D. Maybe this is false E. Somewhat sure this is false F. Very sure this is false 1 H 2 What is the geometry of the transition state in a E2 reaction? What are good models for the transition state of an E2 reaction? O H H H Br CH2CH3 H R O H R CH2CH3 H H H Br O H H H 3C Br R O H R O H R CH3 H H H3C Br CH3 H CH3 H H H3C Br a partially formed -bond in the transition state 3 a partially formed -bond in the transition state 4 Why does this reaction proceed through a anti periplanar transition state? Why does this reaction proceed through a anti periplanar transition state? O H H H3C Br R O H R O H H H3C Br R O H R CH3 H CH3 H H H3C Br CH3 H CH3 H H H3C Br C-H and C-Br bonds are anti periplanar a partially formed -bond in the transition state 5 a partially formed -bond in the transition state 6 1 10/24/2009 Which of the following is a major reason why 2-butene is the major product of this reaction. A. It is produced at a faster rate. (kinetics) B. It is more stable. (thermodynamics) What is the approximate Keq for the following reaction? What 1-butene trans-2-butene Keq = trans-2-butene 1-butene A. A. Keq = 1 H OEt H OEt B. Keq = 4 C. Keq = 40 D. Keq = 100 E. Keq = 1000 19% energy Br anti periplanar transition state energy Br Br Br anti periplanar transition state Keq ~ 1012/5.7 = 127 reaction reaction 12 kJ/mol 81% Why is there 19% of 1-butene in this elimination reaction when there is less than 1% at equilibrium? 127 = 1-butene trans-2-butene Changing the base from ethoxide to t-butoxide increases the proportion of 1-butene. OEt HOEt 19% + 81% Br H OEt energy Br Br anti periplanar transition state 19% Keq ~ 1012/5.7 = 127 reaction 12 kJ/mol 81% A. A. Very sure this is true B. B. Somewhat sure this is true C. Maybe this is true D. Maybe this is false E. Somewhat sure this is false F. Very sure this is false Changing the base from ethoxide to t-butoxide increases the proportion of 1-butene. trans-2-butene 127 = 1-butene CH3 O C CH3 H CH3 Predict the major product of the following reaction. energy Br Br anti periplanar transition state 53% 12 kJ/mol 46% reaction 2 10/24/2009 The % of alkene increases when the ethoxide base is replaced by t-butoxide. Both the SN2 and E2 reactions proceed slower when the ethoxide base is replaced by t-butoxide. A. A. Very sure this is true B. B. Somewhat sure this is true C. Maybe this is true D. Maybe this is false E. Somewhat sure this is false F. Very sure this is false A. A. Very sure this is true B. B. Somewhat sure this is true C. Maybe this is true Predict the major product of the following reaction. Why is the less stable alkene the major product? What is the most stable conformation of the above bromocyclohexane derivative? H CH3 H H H Br Why is the less stable alkene the major product? H CH3 H H H Br CH3 Br Predict the product of the following reaction. CH3 or anti periplanar transition state energy Choose the major product of the above reaction. reaction H H D. Maybe this is false E. Somewhat sure this is false F. Very sure this is false B H CH3 H H H H CH3 H H 18 3 10/24/2009 Which stereoisomer is more reactive? Which stereoisomer is more stable? A H H CH3 H H OH CH3 A H H CH3 H H OH CH3 H H H H B 19 B 20 Which stereoisomer is the more reactive? H H CH3 H H Would a 3° alcohol react A. faster or B. slower than a 2° alcohol? CH3 OH2 energy energy H O H H CH3 H CH3 H reaction 21 reaction 22 Would a 3° alcohol react A. faster or B. slower than a 2° alcohol? Would a 1° alcohol react A. faster or B. slower than a 2° alcohol? 1° cations are very unstable 1° CH3 OH2 CH3 OH2 2° energy energy 3° reaction 23 reaction 24 4 10/24/2009 25 5 ...
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This note was uploaded on 12/25/2009 for the course CHE 320 taught by Professor Ff during the Spring '09 term at SUNY Stony Brook.

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