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feb_24 - These type of reactions are catalyzed by both acid...

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Unformatted text preview: 2/25/2010 These type of reactions are catalyzed by both acid and base. What is the mechanism of the acid catalyzed reaction? H H H O H O H O H O H -H H H H O H O H H H These type of reactions are catalyzed by both acid and base. What is the mechanism of the acid catalyzed reaction? H H H O H O H O H O H -H H H or OH H O H O H H H more reactive C=O H +H H more reactive C=O H +H H O + H H H O O + H H H O What is the first intermediate in this mechanism? O H H O H H O H OH H more reactive nucleophile OH HO H O H H O H H A B H What is the mechanism of the base catalyzed reaction? What is the first step? C There are two forms of formaldehyde in water, the carbonyl compound and its hydrate. In water the hydrate is the dominant form. Keq O + H H H O H H O H O H H H O + H H O H H O H O H H 2000 formaldehyde formaldehyde E ∆G˚ = -RTlnKeq R Would the Keq of acetaldehyde be (A) larger or (B) smaller or (C) the same as formaldehyde? Keq O H H + C H H H O H H H H O C H O H H O H H C H H H H What is the best reason why acetaldehyde is less hydrated than formaldehyde? Keq O + C H H H O H H H H O C H O H H 1.3 acetaldehyde O + H H H O H H O H O H H 2000 H O + H H O H H O H O H H 2000 formaldehyde A. A. The methyl group stabilizes the hydrated form. B. The methyl group stabilizes the C=O group. C. Formaldehyde is not soluble in water. D. Acetaldehyde is not soluble in water. E ∆G˚ = -RTlnKeq R 1 2/25/2010 Would the Keq of acetaldehyde be (A) larger or Would (B) smaller or (C) the same as acetone? Keq O H H + C H H H O H H H H O C H O H H Would the Keq of acetaldehyde be (A) larger or Would (B) smaller or (C) the same as acetone? Keq O H H + C H H H O H H H H O C H O H H 1.3 1.3 acetaldehyde acetaldehyde O H H C H C H H H + H O H H H H O C H O C H H H H H H C H O C H H H + H O H H H H O C H O C H H H H 0.002 acetone acetone Would the Keq of acetaldehyde be (A) larger or Would (B) smaller than trichloroacetaldehyde? Keq O H H + C H H H O H H H H O C H O H H Would the Keq of trichloroacetaldehyde be (A) larger or (B) smaller than acetaldehyde? Keq O H H + C H H H O H H H H O C H O H H 1.3 1.3 acetaldehyde acetaldehyde O Cl Cl C Cl O Cl Cl + C Cl H H O H H acetaldehyde O Cl Cl C Cl O Cl Cl + C Cl H H O H H H Cl Cl O C Cl O H H H Cl Cl O C Cl O H H 2000 trichloroacetaldehyde trichloroacetaldehyde Do alcohols react with carbonyl compounds? Which compound is behaving as the acid? Which arrow is correct? A B H O O H CH3 H O H O CH3 Which of the following is an intermediate on A going from the hemiacetal to the acetal? H O O H H CH3 B H O CH3 O CH3 O H H C H O H H O H O O +H CH3 C ketone H H O H3C O O CH3 CH3 hemiacetal CH3 H3C H O + H H H O O CH3 H O O CH3 O CH3 H H O H3C O O CH3 ? acetal acetal 2 2/25/2010 What are acetals and hemiacetals? hemiacetals? Predict the product of the reaction of water with cyclohexanone in the presence of an acid catalyst. H H O O H CH3 O O +H CH3 H O H CH3 H3C O O CH3 O + H O CH3 H H3C O O + H2O CH3 ketone hemiacetal acetal ketone acetal E R Predict the product of the reaction of water with cyclohexanone in the presence of an acid catalyst. What is the major product of the following reaction? H3C O + H O CH3 H O O CH3 OH OH ketone acetal H O OH O OH2 E R A B C D What is the mechanism of the following reaction? Choose the structure that is an intermediate in the following reaction? H H O A B C D 3 2/25/2010 How many acetals and hemiacetals are present in the carbohydrate lactose? H O O +H CH3 H3C O O + CH3 H2O Acetals and ketals can be used to protect carbonyl groups. hemiacetal HO HO O HO HO O OH O OH lactose OH OH H O OH HO OH H HO O OH acetal O HO H H O H HO CH3 O O +H CH3 H3C O O + CH3 H2O O HO OH OH glucose glucose A acetal hemiacetal 1 0 B 1 1 C 0 1 D 0 0 E 2 0 F 2 1 Acetals and ketals can be used to protect carbonyl groups. How could the following transformation be accomplished? H3C O H H / H2O O O CH3 O 1. 2. H3O OH No Reaction 1. MeOH/H 2. LiAlH4 3. H3O Li 1. 2. H3O Li O NaBH4 MeOH OCH3 O OH H OCH3 1. MeOH/H 2. NaBH4 3. H3O NaBH4 MeOH A B C D How could the following transformation be accomplished? How could the following transformation be accomplished? O O O MeOH/H OCH3 OCH3 LiAlH4 OCH3 OCH3 H3O O O OCH3 H H OH O OCH3 O OCH3 H H O H H OH 1. MeOH/H 2. LiAlH4 3. H3O 1. MeOH/H 2. NaBH4 3. H3O NaBH4 MeOH 1. LiAlH4 2. H3O 1. MeOH/H 2. LiAlH4 3. H3O 1. MeOH/H 2. NaBH4 3. H3O NaBH4 MeOH 1. LiAlH4 2. H3O A B C D A B C D 4 2/25/2010 5 ...
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