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 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 (bisaya ka dong?)

Amine must have 2 protons, RNH2

Problems

Predict the Products!

Problems

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