Chapter 16
I. Reaction of Acyl Halides
A. Most reactive, will form all other carboxylic
acid derivatives.
B. Reaction with ammonia and primary and secondary
amines must be carried out with two equivalents.
II. Reactions of Acid Anhydrides
A. No reaction with chloride ion.
B. Will react with an alcohol, water, and
amines.
III. Reaction of Esters
A. Slow reaction with water: hydrolysis,
slow reaction with an alcohol: transesterification.
1. Must be acid catalyzed
or base enhanced.
2. Equilibrium reaction
can be driven to the right by adding more reactant.
B. Reaction with amines, only one equivalent
is required
C. Mechanism of Acid-Catalyzed Ester Hydrolysis
1. The carbonyl oxygen
is protonated, the nucleophile, water, attacks the protonated carbonyl
group. The resulting protonated tetrahedral intermediate is in equilibrium
with the nonprotonated form. The -OH or the -OR can be protonated
and lost, resulting in the carboxylic acid or the original ester.
2. The H+ increases
the rate of formation of the tetrahedral intermediate, because the protonation
of the carbonyl carbon increases the susceptibility of a nucleophilic attack.
The H+ increases the rate of collapse of the tetrahedral intermediate by
decreasing the basicity of the leaving group.
D. Hydroxide-ion promoted ester hydrolysis
1. Hydroxide ion increases
the rate of formation of the tetrahedral intermediate because HO- is a
better nucleophile. HO- ion also increases the rate of collapse,
because a smaller fraction of the negative tetrahedral intermediate become
protonated.
2. The final product
is a carboxylate rather than a carboxylic acid. The carboxylate ion
is not attacked by a nucleophile, thus the reaction is not reversible.
3. Studies with O18
proves the existence of the tetrahedral intermediate.
IV. Reaction of Carboxylic acids.
A. Fischer esterification, acid catalyzed
equilibrium reaction.
B. Reaction with amines, acid-base reaction
at room temperature, with heat amides are formed.
C. The carboxylate form very unreactive.
V. Reactions of Amides
A. Very unreactive
1. Will react with
water in the presence of acid or base and heat.
2. Will react with
alcohol with acid and heat
3. Will react with
dehydration reagents, P2O5, POCl3, SOCl2, to form nitriles.
B. Mechanism of acid-catalyzed and base promoted
hydrolysis of amides.
1. H+ catalyzes the
nucleophilic attack and decreases the basicity of the leaving group.
2. OH- increases the
rate of nucleophilic attack. If an occasional NH2- group leaves,
it immediately deprotonates the carboxylic acid, driving the equilibrium
to the right.
VI. The Gabriel Synthesis of Primary Amines
VII. Hydrolysis of Nitriles
VIII. Soaps, detergents, and Micelles
IX. Activation of carboxylic acids in the laboratory and in biological systems
X. Dicarboxylic acid derivatives
Chapter 17, Carbonyl Compounds II
I. Nomenclature
A. Aldehydes
1. "al" and carbaldehyde
2. formyl group
B. Ketones
1. "one"
2. oxo group
C. Order of priority: carboxylic acid
(carboxy), ester (alkoxycarbonyl), amide (amido), nitrile (cyano), aldehyde
(formyl), ketone (oxo), alcohol (hydroxy), amine (amino), alkene (alkenyl),
alkyne (alkynyl), alkane (alkyl), ether (alkoxy), alkyl halide (halo).
II. Relative Reactivities of Carbonyl Compounds
A. formaldehyde, aldehyde, ketone
B. Steric Hindrance impede reactivity
C. most reactive: acyl halide, acid
anhydride, aldehyde, ketone, ester ~ carboxylic acid, amide least reactive
III. Nucleophilic Addition Reactions
A. After the nucleophilic attack on the carbonyl
carbon, an alkoxide ion is formed that can be protonated by the solvent.
B. Reaction can be acid catalyzed.
C. Nucleophilic addition-elimination may be
possible
IV. Additions of Carbon Nucleophiles, formation of a C-C bond.
A. Grignard, like the reaction in lab.
B. Addition of Acetylide ion.
C. Addition of Hydroden Cyanide