tb19 - Chapter 19 - Aldehvdes and Ketones: Nucleophilic...

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194 Chapter 19: Aldehydes and Ketones: Nucleophilic Addition Reactions Chapter 19 - Aldehvdes and Ketones: Nucleophilic Addition Reactions Draw structures corresponding to each of the following names: 1. 2,2,2-trichloroethanal (chloral) Answer: a CI, ~ H CI-1' "- CI 2. benzophenone Answer: 0 du '?' I I ~ ~ 3. trans- 3-isopropylcyclohexanecarbaldehyde Answer: )---cfH 4. 5,5-dimethyl-l,3-cyclohexanedione(dimedone) Answer: OVA H3C CH3 5. 2-cyclohexenone Answer: 00
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6. What is the correct structure for 2-hydroxyacetophenone? Circle the letter of your response. ,~ VV 0 '0:: Answer: c Provide IUP AC names for each structure below. 0 7. H NOz Answer: m-nitrobenzaldehyde 8. Answer: 4,8-dimethyl-7 -nonen-2-one 9. ~CH3 Vo Answer: I-pheny 1-2-propanone 10. 0 0 H~H Answer: cis-l,3-cyclopentanedicarbaldehyde 11. ~H Answer: 5-oxoheptanal Test Items for McMurry's Organic Chemistry. Seventh Edition OH 0 ' -0- 11 b. H3C-CH ~ !J C-H d.YH lJlOH 195
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Consider the reaction below to answer the following questions: 0 ! + H2O base catalyst - --- HO OH X 12. Write the complete stepwise mechanism for the reaction shown above. Show all intermediate structures and all electron flow with arrows. Answer: .0. Cllr:§H Ii H(): O:t HO OH ~X: ~OH_X 13. The substance formed on addition of water to an aldehyde or ketone is called a hydrate or alan: Answer: a. b. vicinal diol geminal diol acetal ketal c. d. b 14. The exact position of the equilibrium between ketones/aldehydes and their hydrates depends on the structure of the carbonyl compound. Although the equilibrium favors the carbonyl compound in most cases, cyclopropanone forms a stable hydrate. Explain this phenomenon based on the structures of cyclopropanone and its hydrate. Answer: The carbonyl carbon in cyclopropane is highly strained because the preferred bond angle for an Sp2-hybridized carbon is 120° but the real angle is 60°. This angle strain is somewhat relieved when cyclopropanone is hydrated-the preferred bond angle for an Sp3-hybridized carbon is about 109.5°. Going from Sp2 to Sp3 hybridization relieves angle strain by about 10°. Thus, the hydrate of cyclopropane is more stable than the carbonyl form, and the equilibrium lies to the right in this reaction. 15. Many nucleophilic addition reactions of aldehydes and ketones are catalyzed by acid or base. Bases catalyze hydration by: Answer: 196 a. b. c. d. making the carbonyl group more electrophilic shifting the equilibrium of the reaction making the carbonyl group less electrophilic converting the water to hydroxide ion, a much better nucleophile d Chapter 19: Aldehydes and Ketones: Nucleophilic Addition Reactions
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+ H2O 17. Enamines formed ITomthe cyclic secondary amine pyrrolidine are important intermediates in the synthesis of 1,5-diketones. 0
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tb19 - Chapter 19 - Aldehvdes and Ketones: Nucleophilic...

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