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19.13: Preparation of Amines: Alkylation of Ammonia and Amines

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Organic Chemistry

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Preparation of Amines: Alkylation of Ammonia and Amines

19.13: Preparation of Amines: Alkylation of Ammonia and Amines

Alkylation is one of the methods used to prepare amines. Direct alkylation of ammonia or a primary amine with an alkyl halide gives polyalkylated amines along with a quaternary ammonium salt through successive SN2 reactions. This process of making the quaternary salt through the direct alkylation method is called exhaustive alkylation.

Each alkylation step makes the nitrogen center more nucleophilic, which triggers successive alkylations until a quaternary ammonium salt is formed. Considering this, specific reaction conditions, such as excess ammonia, must be used to exclusively make primary amines.

Since tertiary halides are more hindered, they are not the substrates of choice for alkylation reactions. Although secondary alkyl halides are far less hindered and can be alkylated, they are also not preferred as substrates due to their tendency to undergo elimination reactions.

Since ammonia is cheaply available, alkylations using ammonia as the substrate are the most common.


Amines Alkylation Ammonia Primary Amine Alkyl Halide Polyalkylated Amines Quaternary Ammonium Salt SN2 Reactions Exhaustive Alkylation Nucleophilic Reaction Conditions Excess Ammonia Tertiary Halides Hindered Secondary Alkyl Halides Elimination Reactions

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