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Reactions of Acyl Chlorides with Ammonia

  • Page ID
    3797
  • [ "article:topic", "authorname:clarkj", "showtoc:no" ]

    This page gives you the facts and a simple, uncluttered mechanism for the nucleophilic addition / elimination reaction between acyl chlorides (acid chlorides) and ammonia. Ethanoyl chloride is taken as a typical acyl chloride. Any other acyl chloride will behave in the same way. Simply replace the CH3 group in what follows by anything else you want.

    The reaction between ethanoyl chloride and ammonia

    Ethanoyl chloride reacts violently with a cold concentrated solution of ammonia. A white solid product is formed which is a mixture of ethanamide (an amide) and ammonium chloride.

     

     

    Notice that, unlike the reactions between ethanoyl chloride and water or ethanol, hydrogen chloride isn't produced - at least, not in any quantity. Any hydrogen chloride formed would immediately react with excess ammonia to give ammonium chloride.

    \[ NH_3 + HCl \rightarrow NH_4Cl\]

    The Mechanism

    The first stage (the addition stage of the reaction) involves a nucleophilic attack on the fairly positive carbon atom by the lone pair on the nitrogen atom in the ammonia.

     

     

    The second stage (the elimination stage) happens in two steps. In the first, the carbon-oxygen double bond reforms and a chloride ion is pushed off.

     

     

    That is followed by removal of a hydrogen ion from the nitrogen. This might happen in one of two ways:

    It might be removed by a chloride ion, producing HCl (which would immediately react with excess ammonia to give ammonium chloride as above) . . .

    and

    \[ NH_3 +HCl \rightarrow NH_4Cl\]

    . . . or it might be removed directly by an ammonia molecule.

     

     

    The ammonium ion, together with the chloride ion already there, makes up the ammonium chloride formed in the reaction.

    Contributors

    Jim Clark (Chemguide.co.uk)