Carboxylic Acid Derivatives - Part 1 | Organic Chemistry 2

Carboxylic acid derivatives are studied in this chapter: properties and relative reactivity of carboxylic acid derivatives, chemistry of acyl halides, chemistry of esters, chemistry of carboxylic anhydrides, chemistry of amides

Properties and Relative Reactivities

 

H on an α-carbon of the carbonyl bond is acidic. The pKa depends on the electronegativity of ⇒ the lower the electronegativity, the higher the pKa
Acyl halides: pKa ~ 16; Carboxylic anhydrides: pKa ~ 20; Esters: pKa ~ 25; Amides: pKa ~ 30

Chemistry of Acyl Halides

Nomenclature:

The -oic acid ending of the corresponding carboxylic acid is replace by -oyl halide (halide = fluoride, chloride, bromide, iodide)
 

Reactivity of acyl halides:
 

  1. Formation of carboxylic acids, carboxylic anhydrides, esters and amides:


     

    - NuH = HOH ⇒ carboxylic acid formation
    - NuH = R'COOH ⇒ carboxylic anhydride formation
    - NuH = R'OH ⇒ ester formation
    - NuH = R'HNH ⇒ amide formation

    Mechanism: addition-elimination
     

  2. Formation of ketones:


    Mechanism: addition-elimination
     

  3. Formation of aldehydes:



    Mechanism: addition-elimination

Chemistry of Esters

Nomenclature:

The alkyl chain R' is named as a substituent. This is followed by the name of the parent chain (RC) where the -ane ending of the corresponding alkane is replaced by -oate

 

Reactivity of esters:
 

  1. Formation of carboxylic acids, esters and amides:


     

    - NuH = HOH ⇒ carboxylic acid formation
    - NuH = R''OH ⇒ new ester formation (Transesterification)
    - NuH = R''HNH ⇒ amide formation

    Mechanism: addition-elimination
     

  2. Formation of alcohols:
     

     

  3. Formation of aldehydes:
     

     
     

Chemistry of Carboxylic Anhydrides

Nomenclature:

Add the term anhydride to the name of the corresponding carboxylic acid
 

Reactivity of carboxylic anhydrides:
 

  1. Formation of carboxylic acids, esters and amides:


     

    - NuH = HOH ⇒ carboxylic acid formation
    - NuH = R'OH ⇒ ester formation
    - NuH = R'HNH ⇒ amide formation

    Mechanism: addition-elimination

Chemistry of Amides

Nomenclature:

The -ane ending of the corresponding alkane is replace by -amide. Substituents on nitrogen are indicated as prefixes preceded by N- or N,N- (if 2 similar groups)
 

Reactivity of amides:
 

  1. Formation of carboxylique acids:



    Mechanism: addition-elimination
     
  2.  Formation of amines:


     
  3.  Formation of aldehydes: