organic chemistry for medicine and biology students chem 2311 chapter 19 & 20 carboxylic acids...
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Organic chemistry for medicine and biology students
Chem 2311
Chapter 19 & 20
Carboxylic acids and Their Derivatives
By Prof. Dr.
Adel M. Awadallah
Islamic University of Gaza
Diacids
Physical Properties of carboxylic acids
Hydrogen bonding
Solubility in water
(lower acids)
Acidity of carboxylic acids
pKa = -log Ka
As Ka increase or pKa decrease, the acidity increase
Resonance and Inductive effect
Conversion of acids to salts
Preparation of carboxylic acids
Acids, hydroxy acids, amino acids, and unsaturated acids from cyanohydrines
Reactions of carboxylic acids
Hell-Volhard-Zelinsky Reaction
Treatment with bromine and a catalytic amount of phosphorus leads to the selective α-bromination of carboxylic acids.
Mechanism of the Hell-Volhard-Zelinsky ReactionPhosphorus reacts with bromine to give phosphorus tribromide, and in the first step this converts the carboxylic acid into an acyl bromide.
EstersNomenclature
Examples
O
OMe H
OO
OPh
O
OEt
CH3 O
O
Cl
OEt
OH
CH3CH3 O
O
Lactones (Cyclic Esters)
Reactions of Esters with Grignard Reagent
Formation of Amides (Ammonolysis of Esters)
Reduction of EstersEsters can be reduced to primary alcohols
The Cliasen Condensation
Acid HalidesThey are prepared from the reaction of acids with thionyl chloride or
phosphorus halides
Reactions of acid chloridesAcid chlorides react rapidly with most nucleophiles such as water,
alcohols and ammonia
Acyl halides have irritating odors. Benzoyl chlorid is a lachrymator
(tear gas)
CH3 Cl
O
CH3 OH
O
CH3 OR
O
CH3 NH2
O
H2O
EtOH
NH3
+
+
+
HCl
HCl
HCl
Reaction with Grignard Reagent
Preparation of mixed anhydrides
• Mixed anhydrides CH3 O
OO
Ph
Acetic benzoic anhydride
Nucleophilic substitution of anhydrides
Amides
• Nomenclature
• Properties of Amides
Amide Resonance
Reactions of Amides (Hydrolysis and Reduction)
