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Organic Chemistry 6 th Edition Paula Yurkanis Bruice

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Chapter 18 Carbonyl Compounds II Reactions of Aldehydes and Ketones More Reactions of Carboxylic Acid Derivatives Reactions of a , b -Unsaturated Carbonyl Compounds. Organic Chemistry 6 th Edition Paula Yurkanis Bruice. Nomenclature of Aldehydes.

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Chapter 18

Carbonyl Compounds II

Reactions of Aldehydes and Ketones

More Reactions of Carboxylic Acid Derivatives

Reactions of a,b-Unsaturated Carbonyl Compounds

Organic Chemistry

6th Edition

Paula Yurkanis Bruice


If a compound has two functional groups, the one with the

lower priority is indicated by its prefix:


Nomenclature of Ketones

The carbonyl is assumed to be at the 1-position in cyclic



If a ketone has a second functional group of higher


A few ketones have common names:


The partial positive charge on the carbonyl carbon causes

that carbon to be attacked by nucleophiles:

An aldehyde has a greater partial positive charge on its

carbonyl carbon than does a ketone:

aldehydes are more reactive than ketones
Aldehydes Are More Reactive Than Ketones
  • Steric factors contribute to the reactivity of an aldehyde.
  • The carbonyl carbon of an aldehyde is more accessible
  • to the nucleophile.
  • Ketones have greater steric crowding in their transition
  • states, so they have less stable transition states.

Carboxylic acid derivatives undergo nucleophilic acyl

substitution reactions with nucleophiles:


Aldehydes and ketones undergo nucleophilic addition

reactions with nucleophiles:

This is an irreversible nucleophilic addition reaction if the nucleophile is a strong base


Formation of a New Carbon–Carbon

Bond Using Grignard Reagents

Grignard reagents react with aldehydes, ketones, and

carboxylic acid derivatives



+ NH3


Reaction of Acetylide Ions with Carbonyl Compounds


Mechanism for the reaction of an ester with hydride ion:

Esters and acyl chlorides undergo two successive

reactions with hydride ion and Grignard reagents


The reduction of a carboxylic acid with LiAlH4 forms a

single primary alcohol:

Acyl chloride is also reduced by LiAlH4 to yield an alcohol


An amide is reduced by LiAlH4 to an amine

Mechanism for the reaction of an N-substituted amide

with hydride ion:


Compared with Grignard reagents and hydride ion, CN– is

a relatively weak base; therefore, in basic solution…


Aldehydes and ketones react with a primary amine to

form an imine:

This is a pH-dependent nucleophilic addition–elimination reaction


Dependence of the rate of the reaction of acetone with

hydroxylamine on the pH of the reaction: a pH-rate profile

Maximum rate is at pH = pKa of +NH3OH;

at this pH, both [H+] and [NH2OH] have the highest values

Decreasing rate: [H+] is decreasing

Decreasing rate: [NH2OH] is decreasing

Composition of the rate- determining step:


Aldehydes and ketones react with secondary amines to

form enamines:

An enamine undergoes an acid-catalyzed hydrolysis to

form a carbonyl compound and a secondary amine


Deoxygenation of the Carbonyl Group

Called the Wolff–Kishner reduction


The equilibrium constant for the reaction depends on the

relative stabilities of the reactants and products:


Addition of an Alcohol to

an Aldehyde or a Ketone


Utilization of Protecting Groups

in Synthesis

LiAlH4 will reduce the ester to yield an alcohol, but

the keto group will also be reduced


The keto group is protected as a ketal in this synthesis:

The more reactive aldehyde is protected with the diol

before reaction with the Grignard reagent:


The synthetically useful aldehyde anion does not exist

But its equivalent is accessible via the thioacetal:


Formation of Alkenes:

The Wittig Reaction


Preparation of the Phosphonium Ylide

The phosphonium ylide should be prepared from

sterically hindered alkyl halide:

Synthetic target:

Preferred synthetic approach:


The Wittig reaction is completely regioselective.

  • This reaction is the best way to make a terminal alkene.
  • Stable ylides form primarily E isomers, and unstabilized
  • ylides form primarily Z isomers.
  • Stable ylides have a group (C=O) that can share the
  • carbanion’s negative charge.



Stereochemistry of

Nucleophilic Addition Reaction


Disconnections, Synthons, and

Synthetic Equivalents


Nucleophiles that form unstable addition products form

  • conjugated addition products, because the conjugate
  • addition is not reversible.
  • Nucleophiles that form stable addition products can
  • form direct addition products or conjugate addition
  • products.
  • If the rate of direct addition is slowed down by steric
  • hindrance, a Grignard reagent will form the conjugate
  • addition product.

Strong bases form direct addition products with reactive

carbonyl groups and conjugate addition products with

less reactive carbonyl groups:

addition reactions to a b unsaturated carbonyls
Addition Reactions to a,b-Unsaturated Carbonyls
  • Michael addition nucleophiles:
  • Cyanide
  • Sulfide
  • Organocuprate
  • Amine
  • Halides
  • Direct addition nucleophiles:
  • Grignard
  • LAH
  • Organolithiums