21. Aldehydes and Ketones: Nucleophilic Addition

Identify the bonds broken and formed in the following addition reaction.

(a) Would you expect this reaction to be favored based on entropy?

(b) Based on enthalpy [qualitatively]?

(c) Overall?

The following reaction is known as the benzoin condensation. The reaction does not take place if sodium hydroxide is used instead of sodium cyanide. Propose a mechanism for the reaction and explain why the reaction does not occur if hydroxide ion is the base.

Predict the products formed when cyclohexanone reacts with the following reagents.

(k) sodium cyanide

Suggest a carbonyl to react with NaCN/HCN to produce the following cyanohydrins.

(a)

How would you synthesize the cyanohydrin shown?

Which of the following secondary alcohols can be prepared by the reaction of methyl formate with excess Grignard reagent?

Show how the following compounds can be synthesized from cyclohexanol.

a. b. c.

Propose a mechanism for each of the following reactions:

a.

Predict the products formed when cyclohexanecarbaldehyde reacts with the following reagents.

(a) PhMgBr, then H₃O⁺

LOOKING AHEAD CHAPTERS 8, 17 In Chapters 8 and 17 we learn two reaction for the synthesis of the alcohol shown. (a) Show a mechanism for each of the reactions. (b) If you were designing a synthetic route, which would be considered more sustainable? Consider all factors. [Assume the starting organic molecules are equally green.]

Rank the following compounds from largest K_eq to smallest K_eq for hydrate formation:

Can the rate of hydrate formation be increased by hydroxide ion as well as by acid? Explain.

Which of the following are a. hemiacetals? b. acetals? c. hydrates?

4.

Rank the following carbonyl compounds in order of increasing equilibrium constant for hydration:

CH₃COCH₂Cl ClCH₂CHO CH₂O CH₃COCH₃ CH₃CHO