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)