Aldehydes and Ketones

Carbonyl Compounds

Compounds with C=O

Aledhyde vs Ketone Reactivity

Aldehydes (Y=H) are more reactive than ketones (Y=C) since they are less sterically hindered.

Carbonyl Compound reaction with a nucleophile (aldehydes and ketones vs non)

Adding Alcohols to aldehydes and ketones

Basic conditions create a Hemiacetal (aldehyde) or Hemiketal (ketone)

Hemiacetal

Hemi = half

Acetal has 2 OR groups, so this is half one of those.

Created from a aldehyde reaction

Hemiketal

Hemi = half

Acetal has 2 OR groups, so this is half one of those.

We have a carbon group vs the H in a hemiacetal.

Created from a ketone reaction

BASIC CONDITIONS (adding alcohols to aldehydes and ketones)

• Aldehyde or Ketone

• Basic Conditions

• Alcohol

Quench

• Water or Slightly acedic water

ACIDIC CONDITIONS (adding alcohols to aldehydes and ketones)

• Acidified Alcohol (HOR)

• Acid Source (H+)

Full acetal group

Abundance of Solvent

Aldehydes or Ketones (alcohols) Acidic and Basic Wrapup

Why do ketals or Acetals matter?

They can help protect aldehyde and ketone C=O during synthesis.

We see in the image that it protects it from LiAlH4

Adding 1^o amines to form imines (schiff bases)

Schiff Bases reaction mechanism

Enamines (2^o amines) with aldehydes and ketones

Enamine Mechanism

What happens if you have a non-symmetrical (asymmetric) ketone? Enamines

The enamine will generally be less substituted. Antizaistev.

NaBH4 to aldehydes and ketones

NaBH4, EtOH, Quencher (H3O+)

Changes Carbonyl (C=O) into a OH (alcohol)

LiAlH4 (aldehydes and ketones)

Same reaction as NaBH4

However, LiAlH4 is much stronger

LiAlH4

Only it can reduce all the way to a primary alcohol (gets rid of OH or ester) and reduces to an OH.

NaBH4 as a carboxylic acid reducer

IT CANNOT, it is not strong enough.

Grignard Reagent.

Just add the R group. (with the quench)

CANNOT RUN WITH PROTIC SOLVENT (it will just get protenated)

Organolithium (R,Li)

EXACT SAME AS GRIGNARD.


CANNOT RUN WITH PROTIC SOLVENT (it will just get protenated)

Wittig Reaction

Phosphonium ylide

Turns C=O into C=C

Wittig Reaction Mechanism

How to make Phosphonium Ylide

PPh3 with an alkyl halude, then deprotenate using a BuLi.

(1,2 addition)

1,4 Conjugate or Michael Addition

Michael Addition general trend

Michael addition nucleophiles (that prefer it)

Slightly Weaker Nucleophiles Prefer it

• -C(Triple bond)N

  • Cyanide

• HNR2

  • Amines with one lone pair

• R2CuLi (Li acts like an R-)

  • Acts like a grignard except they preferentially use 1,4.

• HSR (sulfides)

Direct 1,2 addition

• NaBH4 (H- source)

• LiAlH4 (H- source)

• RMgX (Grignard)

What is the fastest when it comes to Nuclophillic addition the fastest?

The most EN

Order of reactivity for carbonyls (for nucleophiles) (most nucleophillic)

Aldehyde > Ketone > Carboxylic Acid

Most electrophilic carbonyls.

Due to resonance, they WANT ELECTRONS more than they want nucleophiles.

• They also have more steric hinderance, which makes it hard for Nucs to get in.