Aldehyde, Ketone and Amine Reactions
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46 Terms
Which is more reactive, an aldehyde or a ketone?
Aldehydes.
Why are aldehydes more reactive?
Less steric hindrance and a larger partial positive charge.
What reagent oxidizes a 1° alcohol to an aldehyde?
PCC or Dess-Martin periodinane.
What reagent oxidizes a 2° alcohol to a ketone?
Common oxidizing agents.
What does NaBH₄ reduce an aldehyde to?
A 1° alcohol.
What does NaBH₄ reduce a ketone to?
A 2° alcohol.
What does LiAlH₄ reduce aldehydes/ketones to?
Alcohols.
Are NaBH₄ and LiAlH₄ reductions reversible?
No.
What reagent forms new C-C bonds with carbonyls?
Grignard reagent (RMgX).
Formaldehyde + Grignard gives what?
A 1° alcohol.
Aldehyde + Grignard gives what?
A 2° alcohol.
Ketone + Grignard gives what?
A 3° alcohol.
What reagent forms cyanohydrins?
CN⁻ (cyanide).
What two groups are present in a cyanohydrin?
OH and CN.
Is cyanohydrin formation reversible?
No.
What is a hydrate?
A carbon bearing two OH groups.
Is hydration reversible?
Yes.
Which form is favored in hydration equilibrium?
The carbonyl.
Which aldehydes readily form hydrates?
Formaldehyde and trichloroacetaldehyde.
What does Tollens reagent oxidize?
Aldehydes only.
What indicates a positive Tollens test?
Silver mirror (Ag).
Do ketones react with Tollens reagent?
No.
What is a hemiacetal?
A carbon with one OR and one OH group.
What is an acetal?
A carbon with two OR groups.
How do you drive acetal formation forward?
Use excess alcohol and remove water.
Why are acetals useful?
They protect aldehydes and ketones.
How are acetals removed?
Aqueous acid (H₃O⁺).
What reagent removes thioacetals?
Raney nickel/H₂.
Primary amine formula?
RNH₂.
Secondary amine formula?
R₂NH.
Tertiary amine formula?
R₃N.
Are amines acidic or basic?
Basic.
Why are amines nucleophilic?
Nitrogen has a reactive lone pair.
What do primary amines form with carbonyls?
Imines.
What do secondary amines form with carbonyls?
Enamines.
Recommended pH for imine/enamine formation?
About pH 4-5.
Overall result of reductive amination?
Carbonyl → amine.
What reagent is used in the Wolff-Kishner reduction?
NH₂NH₂, base, heat.
What reagent is used in the Clemmensen reduction?
Zn(Hg), HCl.
Overall result of Wolff-Kishner/Clemmensen?
Carbonyl → CH₂.
What does the Wittig reaction convert?
Carbonyl → alkene.
What reagent is required for the Wittig reaction?
Phosphorus ylide.
What type of addition does a Grignard perform?
1,2-addition.
What type of addition does a cuprate perform?
1,4-conjugate addition.
What reagent performs 1,4 carbon addition?
R₂CuLi (Gilman reagent).
Does conjugate addition require an acid catalyst?
No.