Ketones, Aldehydes CH21 PS CLASS
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Ketones, Aldehydes
CH21 PS CLASS
Recall the many times we’ve synthesized these! I command thee.
• Oxidation of R-OH – (Periodinane, CrO3/Na2Cr2O7)
• Hydration of Alkynes (keto-enol tautomerism)– H3O+/HgSO4, BH3/H2O2,OH-, etc…
• Friedel-Crafts ACYLation of Aromatics – (acid halide + AlCl3)
REACTIONS OF ALDEHYDES/KETONES
• Oxidation of Aldehydes• Nucleophilic Additions (overview)– Hydride (H-) and Grignard (R-) as Nucleophiles– Water addition (hydrate/diol/geminal diol
formation)– Alcohol addition (acetal formation)– Amine addition (imine formation)
• Conjugate Nucleophilic Addition Reactions
Major Synthesis
Major Synthesis
Major Synthesis
Major Synthesis
Major Synthesis
Major Synthesis
Major Synthesis
Oxidation of Aldehydes
Where [O] = CrO3 among others.
Nucleophilic Addition Rxns
Slightly different mechanisms in acid or base. Neutral vs. Negatively charged Nucleophile
General picture (basic):
Reactivity Notes:
Less steric hindrance with aldehyde
Benzaldehyde less reactive due to resonance stabilization.
Reduction of Ketones/Aldehydes
Addition of Grignard Reagent
Grignard Reagents + carbonyls
Practice!
COME UP WITH PAIRS, More than one answer for some.
Practice!
Hydrate formation/ Geminal Diols
Basic vs. Acidic
BASIC: Strong nucleophile attacks, as in Nu-
ACIDIC:Carbonyl is converted to a stronger ELECTROPHILE as CABON BECOMES MORE POSITIVE.
Problem
Acetal formation
ACID CATALYZED… AGAIN, CARBONYL MADE INTO BETTER ELECTROPHILE.
Acetal Formation
Acetal Formation2 alcohols/ 1 diol can be used to ‘protect’ an aldehyde or ketone from a reaction.
Nuc. Addition of Amines to form: Imines
Amine must have 2 protons, RNH2
If amine is 2° we form enamines
If amine is 2° we form enamines
If amine is 2° we form enamines
Practice addition of amines:
Practice addition of amines:
Problems
Predict the Products!
Problems
Wittig reaction, addition of R:- to C=O forming C=C
Limits of SN2???
Addition of ylides
Exercises
Exercises
Conjugate Nucleophilic Addition Rxns
Conjugate Nucleophilic Addition Rxns
THE DOUBLE BOND IS EFFECTIVELY “POLARIZED” INTO A NEGATIVE REGION THAT’S RESONANCE STABILIZED, AND A POSITIVE REGION AT THE BETA-CARBON.
Predict the product
+ HCN
Practice
Predict the Products
a. NaBH4/H3O+b. NH2OH/HClc. 2 CH3OH /acidd. CH3MgBr then acid
Predict the Products
NaBH4/H3O+ NH2OH/HCl
2 CH3OH /acid CH3MgBr then acid
Predict the Products
NaBH4/H3O+ NH2OH/HCl
2 CH3OH /acid CH3MgBr then acid
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
Exercises
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