10-22 - 10/22/2010 In reaction (2) is the percentage of...

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Unformatted text preview: 10/22/2010 In reaction (2) is the percentage of alkene (A) higher or (B) lower than in reaction (1). (1) What is the mechanism of reaction (1)? (1) H A = SN2 and E2 B = SN1 and E2 C = SN2 and E1 D = SN1 and E1 (2) (2) H 1 2 What is the mechanism of reaction (2)? (1) A = SN2 and E2 B = SN1 and E2 C = SN2 and E1 In reaction (2) is the percentage of alkene (A) higher or (B) lower than in reaction (1). (1) D = SN1 and E1 (2) H H Br O 3 (2) 4 C C C C What is the name of the following alkene? What is the name of the following alkene? A. cis-9-octadecene B. trans-9-octadecene A. cis-9-chloro-9-octadecene B. trans-9-chloro-9-octadecene C. none of the above 5 6 1 10/22/2010 C C C C What is the name of the following alkene? What is the name of the following alkene? A. (9Z)-9-chloro-9-octadecene B. (9E)-9-chloro-9-octadecene Highest priority on the same side = zusammen = (Z) Highest priority on opposite sides = entgegen = (E) 7 A. elaidic acid B. (9E)-9-chloro-9-octadecene C. cis-8-octadecene D. trans-8-octadecene 8 C C C C Oleic acid has a higher melting point than elaidic acid. elaidic elaidic acid oleic acid Oleic acid has a higher melting point than elaidic acid. elaidic elaidic acid oleic acid (E)-octadec-9-enoic acid A. Very sure this is true B. Very sure this is false (Z)-octadec-9-enoic acid mp = 44˚C, solid mp = 13˚C, liquid 9 Does oleic acid have the (Z) or (E) configuration? C C C C Oleic has a higher melting point than linolenic acid. linolenic acid oleic oleic acid Oleic has a higher melting point than linolenic acid. Why Why is linolenic acid called an omega 3-fatty acid? mp = -11˚C A. Very sure this is true B. Very sure this is false mp = 13˚C α 1 3 ω 2 11 12 2 10/22/2010 C C C C Oleic acid is more stable than elaidic acid. Elaidic acid is more stable than oleic acid because of steric effects. elaidic elaidic acid A. Very sure this is true B. Very sure this is false oleic acid elaidic elaidic acid A. Very sure this is true B. Very sure this is false oleic acid C C How can we determine the energy differences of the following compounds? Elaidic acid is more stable than oleic acid because of steric effects. A. Measure their boiling points. B. Measure their melting points. elaidic acid oleic acid C. Measure their optical rotations. D. Measure their heats of hydrogenation. non non bonded interactions steric effects Catalytic hydrogenation of cis and trans 2-butene both give butane. Hydrogenation of the trans isomer releases more heat than A. True B. False the cis isomer. H C H3C C H H2 Pd/C H° = -115 kJ/mol CH3 The most stable butene isomer is 1-butene . A. True B. False H C H3C C CH3 H H2 Pd/C H° = -115 kJ/mol H C H3C C H CH3 H2 H3C CH2 CH2 CH3 Pd/C H° = -120 kJ/mol H C H3C C H CH3 H2 H3C CH2 CH2 CH3 Pd/C H° = -120 kJ/mol 3 10/22/2010 The most stable butene isomer is 1-butene . A. True B. False H C H3C H C C H CH3 ΔH° = -120 kJ/mol C CH3 H H3C H C H C H C H H How much more stable is trans 2-butene? H3C H C H3C C CH3 H H C H C H C H H ΔH° = -127 kJ/mol H C C H CH3 5 kJ/mol ΔH° = -120 kJ/mol energy H3C ΔH° = -115 kJ/mol energy H3C ΔH° = -115 kJ/mol H3C CH2 CH2 CH3 H3C CH2 CH2 CH3 Is it possible to determine the % of the cis isomer present at equilibrium at room temperature? H C H3C C H H3C CH3 H C C CH3 H At equilibrium what is the approximate percent of cis-butene? H C H3C C CH3 H H C H3C C H CH3 5 kJ/mol = ∆H˚ ΔG° = ΔH° - TΔS° ΔG° ~ ΔH° 5 kJ/mol = ∆H˚ ΔG° = ΔH° - TΔS° ΔG° ~ ΔH° ΔG° = -RTln Keq ΔG° = -RTln Keq If Keq = 10 then the ΔG° = 5.7 kJ/mole. Keq ~ 105/5.7 = 100.88 = 7.5 A = ~0.1% B = ~1% C = ~10% D = ~50% E = ~99.9% 1-Butene is least stable because of greater steric interactions. A. True B. False H C H3C H C C H CH3 C CH3 H H C H H3C H C C H H Why is cis-2-butene more stable than 1-butene? H C H3C C H H3C CH3 H C H C H C H H 7 kJ/mol 5 kJ/mol energy H3C H H3C H H3C CH2 CH2 CH3 C C H C H H 4 10/22/2010 If there is no bond to the hydrogen atoms in these alkenes why don’t they just drift away? Hyperconjugation is an electronic effect where electron delocalization occurs between alkyl groups attached to sp2 atoms. H C H H C H H C H C H H H3C H C H C H C H H H H H C C H H C H C H H H3C H C H C H C H H Hyperconjugation is an electronic effect where electron delocalization occurs between alkyl groups attached to sp2 atoms. molecular orbital resonance model model Hyperconjugation is an electronic effect where electron delocalization occurs between alkyl groups attached to sp2 atoms. molecular orbital resonance model model energy LUMO H H3C H C C H C H H H HOMO H3C H C C H C H H Trans- cyclohexene is more stable than cis- cyclohexene. A. Very sure this is true B. Very sure this is false 5 ...
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This note was uploaded on 12/05/2010 for the course CHE 321 taught by Professor Fowler/sampson during the Fall '08 term at SUNY Stony Brook.

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