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16.2: Naming and Drawing Amines

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    381514

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    Learning Objectives
    • Objective 1
    • Objective 2

    The common names for simple aliphatic amines consist of an alphabetic list of alkyl groups attached to the nitrogen atom, followed by the suffix -amine. (Systematic names are often used by some chemists.) The amino group (NH2) is named as a substituent in more complicated amines, such as those that incorporate other functional groups or in which the alkyl groups cannot be simply named.

    Example \(\PageIndex{1}\)

    Name and classify each compound.

    1. CH3CH2CH2NH2
    2. Diagram showing "Causation" at the top, leading downward to "Correlation" below.
    • CH3CH2NHCH2CH3
    • CH3CH2CH2NHCH3
    Solution
    1. There is only one alkyl group attached to the nitrogen atom, so the amine is primary. A group of three carbon atoms (a propyl group) is attached to the NH2 group through an end carbon atom, so the name is propylamine.
    2. There are two methyl groups and one ethyl group on the nitrogen atom. The compound is ethyldimethylamine, a tertiary amine.
    3. There are two ethyl groups attached to the nitrogen atom; the amine is secondary, so the compound is diethylamine.
    4. The nitrogen atom has a methyl group and a propyl group, so the compound is methylpropylamine, a secondary amine.
    Exercise \(\PageIndex{1}\)

    Name and classify each compound.

    1. Text displaying "ON" and "OFF" with an arrow pointing from "ON" to "OFF."
    • Text graphic with the phrase "OF COURSE!" in a bold font, placed above an illustrated speech bubble with "?" inside.

    • CH3CH2CH2CH2NH2

    • CH3CH2CH2NHCH2CH2 CH3

    Example \(\PageIndex{2}\)

    Draw the structure for each compound and classify.

    1. isopropyldimethylamine
    2. dipropylamine
    Solution
    1. The name indicates that there are an isopropyl group (in red) and two methyl groups (in green) attached to the nitrogen atom; the amine is tertiary.
      Chemical structure diagram featuring a carbon chain with functional groups, labeled with elemental symbols and bonds.
    • The name indicates that there are two propyl groups attached to the nitrogen atom; the amine is secondary. (The third bond on the nitrogen atom goes to a hydrogen atom.) CH3CH2CH2NHCH2CH2CH3
    Exercise \(\PageIndex{2}\)

    Draw the structure for each compound and classify.

    1. ethylisopropylamine
    2. diethylpropylamine

    The primary amine in which the nitrogen atom is attached directly to a benzene ring has a special name—aniline. Aryl amines are named as derivatives of aniline.

    Chemical structure diagrams of three compounds: aniline, 2-chloroaniline, and 3-chloroaniline.
    Example \(\PageIndex{3}\)

    Name this compound.

    Chemical structure of phenol, featuring a benzene ring with a hydroxyl group (-OH) attached.
    Solution

    The benzene ring with an amino (NH2) group is aniline. The compound is named as a derivative of aniline: 3-bromoaniline or m-bromoaniline.

    Exercise \(\PageIndex{3}\)

    Name this compound.

    Chemical structure of benzene, featuring a hexagonal ring with alternating double bonds and a functional group attached.
    Example \(\PageIndex{4}\)

    Draw the structure for p-ethylaniline and classify.

    Solution

    The compound is a derivative of aniline. It is a primary amine having an ethyl group located para to the amino (NH2) group.

    Chemical structure of a molecule featuring a hexagonal carbon ring with attached functional groups.
    Exercise \(\PageIndex{4}\)

    Draw the structure for p-isopropylaniline and classify.

    Example \(\PageIndex{5}\)

    Draw the structure for 2-amino-3-methylpentane.

    Solution

    Always start with the parent compound: draw the pentane chain. Then attach a methyl group at the third carbon atom and an amino group at the second carbon atom.

    Chemical reaction diagram illustrating the conversion of reactants to products with molecular formulas.
    Exercise \(\PageIndex{5}\)

    Draw the structure for 2-amino-3-ethyl-1-chloroheptane.

    Ammonium (NH4+) ions, in which one or more hydrogen atoms are replaced with alkyl groups, are named in a manner analogous to that used for simple amines. The alkyl groups are named as substituents, and the parent species is regarded as the NH4+ ion. For example, CH3NH3+ is the methylammonium ion. The ion formed from aniline (C6H5NH3+) is called the anilinium ion.

    Example \(\PageIndex{6}\)

    Name each ion.

    1. CH3NH3+
    2. (CH3)2NH2+
    3. (CH3)3NH+
    4. (CH3)4N+
    Solution

    The ions have one, two, three, and four methyl (CH3) groups attached to a nitrogen atom. Their names are as follows:

    1. methylammonium ion
    2. dimethylammonium ion
    3. trimethylammonium ion
    4. tetramethylammonium ion
    Exercise \(\PageIndex{6}\)

    Name each ion.

    1. CH3CH2NH3+
    2. (CH3CH2)3NH+
    3. (CH3CH2CH2)2NH2+
    4. (CH3CH2CH2CH2)4N+

    Summary

    An amine is a derivative of ammonia in which one, two, or all three hydrogen atoms are replaced by hydrocarbon groups. The amine functional group is as follows:

    Four horizontal lines with varying lengths and line weights, illustrating different types of line drawings.

    Amines are classified as primary, secondary, or tertiary by the number of hydrocarbon groups attached to the nitrogen atom. Amines are named by naming the alkyl groups attached to the nitrogen atom, followed by the suffix -amine.

    16.2: Naming and Drawing Amines is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.