Organic Chemistry

Section 17.8 Reactions of Acyl Halides 687

In the conversion of an acyl chloride into an ester, the nucleophilic alcohol attacks
the carbonyl carbon of the acyl chloride. Because the protonated ether group is a
strong acid (Section 1.17), the tetrahedral intermediate loses a proton. Chloride ion is
expelled from the deprotonated tetrahedral intermediate because chloride ion is a
weaker base than the alkoxide ion.

The reaction of an acyl chloride with ammonia or with a primary or secondary
amine forms an amide and HCl. The acid generated in the reaction will protonate un-
reacted ammonia or unreacted amine; because they are not nucleophiles, the protonat-
ed amines cannot react with the acyl chloride. The reaction, therefore, must be carried
out with twice as much ammonia or amine as acyl chloride so that there will be enough
amine to react with all the acyl halide.

Because tertiary amines cannot form amides, an equivalent of a tertiary amine such as
triethylamine or pyridine can be used instead of excess amine.

++CH 3 NH 2

+

pyridine

CH 3 CH (^3) N
H
Cl−
N
Cl NHCH 3
C
O
C
O
O
−

• 
  
  
  
  • O
    −
    Cl O
    CH 3 CCl Cl
    O
    CO
    CH 3
    O
    −
    mechanism for the conversion of an acyl chloride into an acid anhydride
    CH 3
    C
    O
    CH 3
    C
    O
    CH 3 CH 3
    C
    O
    C
    OCH 3
    mechanism for the conversion of an acyl chloride into an ester
  
  
  
  


• CH 3 OH CH 3 CH 3
  OCH 3
  C + Cl−
  H B HB+
  Cl
  O−
  OCH 3
  CCl
  O−
  CH 3 Cl
  C
  O
  CH 3
  C
  O


• 
  

  Cl

  
  


• NH 3
  CH 3 NH 2
  NH 3


• HCl NH 4 Cl−


• 
  

  Cl
  2 CH 3 NH
  CH 3

  
  


• 
  

  CH 3 CH 2

  
  


• CH 3 NH 2
  CH 3 NH 2


• CH 3 NH 3 Cl−


• 
  

  NCH 3
  CH 3 NH 2 Cl−
  CH 3

  
  


• 
  


• 
  

  CH 3
  C
  O
  Cl
  C
  O
  CH 3 CH 2 NHCH 3
  C HCl
  O
  C
  O
  C
  O
  CH 3
  C
  O