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16.5: Basicity of Amines

  • Page ID
    86282
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    Learning Objectives

    • Name the typical reactions that take place with amines.
    • Describe heterocyclic amines.

    Recall that ammonia (NH3) acts as a base because the nitrogen atom has a lone pair of electrons that can accept a proton. Amines also have a lone electron pair on their nitrogen atoms and can accept a proton from water to form substituted ammonium (NH4+) ions and hydroxide (OH) ions:

    ammonium.jpg

    As a specific example, methylamine reacts with water to form the methylammonium ion and the OH ion.

    methylammonium ion.jpg

    Nearly all amines, including those that are not very soluble in water, will react with strong acids to form salts soluble in water.

    soluble.jpg

    Amine salts are named like other salts: the name of the cation is followed by the name of the anion.

    Example \(\PageIndex{1}\)

    What are the formulas of the acid and base that react to form [CH3NH2CH2CH3]+CH3COO?

    Solution

    The cation has two groups—methyl and ethyl—attached to the nitrogen atom. It comes from ethylmethylamine (CH3NHCH2CH3). The anion is the acetate ion. It comes from acetic acid (CH3COOH).

    Exercise \(\PageIndex{1}\)

    What are the formulas of the acid and base that react to form (CH3CH2CH2)3NH+I?

    To Your Health: Amine Salts as Drugs

    Salts of aniline are properly named as anilinium compounds, but an older system, still in use for naming drugs, identifies the salt of aniline and hydrochloric acid as “aniline hydrochloride.” These compounds are ionic—they are salts—and the properties of the compounds (solubility, for example) are those characteristic of salts. Many drugs that are amines are converted to hydrochloride salts to increase their solubility in aqueous solution.


    16.5: Basicity of Amines is shared under a CC BY-NC-SA 3.0 license and was authored, remixed, and/or curated by LibreTexts.

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