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Chemistry LibreTexts

20.8: Alkanenitriles: A Special Class of Carboxylic

  • Page ID
    201317
  • Name the parent alkane (include the carbon atom of the nitrile as part of the parent) followed with the word -nitrile. The carbon in the nitrile is given the #1 location position. It is not necessary to include the location number in the name because it is assumed that the functional group will be on the end of the parent chain.

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    Cycloalkanes are followed by the word -carbonitrile. The substituent name is cyano.

    • 1-butanenitrile or 1-cyanopropane

    Try to name the following compounds using these conventions�

    J

    J

    Try to draw structures for the following compounds�

    • butanedinitrile J
    • 2-methycyclohexanecarbonitrile J

    Some common names that you should know are...

    acetonitrile

    benzonitrile

    Try to draw a structure for the following compound�

    • 2-methoxybenzonitrile J

    Contributors

    The electronic structure of nitriles is very similar to that of an alkyne with the main difference being the presence of a set of lone pair electrons on the nitrogen. Both the carbon and the nitrogen are sp hydridized which leaves them both with two p orbitals which overlap to form the two \(\pi\) bond in the triple bond. The R-C-N bond angle in and nitrile is 180° which give a nitrile functional group a linear shape.

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    The lone pair electrons on the nitrogen are contained in a sp hybrid orbital which makes them much less basic and an amine. The 50% character of an sp hybrid orbital close to the nucleus and therefore less basic compared to other nitrogen containing compounds such as amines.

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    The presence of an electronegative nitrogen causes nitriles to be very polar molecules. Consequently, nitriles tend to have higher boiling points than molecules with a similar size.

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    Contributors

    Nitriles can be converted to carboxylic acid with heating in sulfuric acid. During the reaction an amide intermediate is formed.

    General Reaction

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    Example

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    Contributors

    Prof. Steven Farmer (Sonoma State University)

    Grignard reagents can attack the electophillic carbon in a nitrile to form an imine salt. This salt can then be hydrolyzed to become a ketone.

    General Reaction

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    Example

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    Mechanism

    1) Nucleophilic Attack by the Grignard Reagent

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    2) Protonation

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    3) Protonation

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    4) Nucleophilic attack by water

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    5) Proton Transfer

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    6) Leaving group removal

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    7) Deprotonation

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    Contributors

    Prof. Steven Farmer (Sonoma State University)

    Nitriles can be converted to 1° amines by reaction with LiAlH4. During this reaction the hydride nucleophile attacks the electrophilic carbon in the nitrile to form an imine anion. Once stabilized by a Lewis acid-base complexation the imine salt can accept a second hydride to form a dianion. The dianion can then be converted to an amine by addition of water.

    General Reaction

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    Going from reactants to products simplified

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    Example

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    Mechanism

    1) Nucleophilic Attack by the Hydride

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    2) Second nucleophilic attack by the hydride.

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    3) Protonation by addition of water to give an amine

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    Contributors

    Prof. Steven Farmer (Sonoma State University)