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3.4: Using Curved Arrows in Polar Reaction Mechanisms

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    After completing this section, you should be able to use curved (curly) arrows, in conjunction with a chemical equation, to show the movement of electron pairs in a simple polar reaction, such as electrophilic addition.

    Key Terms

    Make certain that you can define, and use in context, the key terms below.

    • electrophlic
    • nucleophlic

    Pushing Electrons and Curved Arrows

    Understanding the location of electrons and being able to draw the curved arrows that depict the mechanisms by which the reactions occur is one of the most critical tools for learning organic chemistry since they allow you to understand what controls reactions, and how reactions proceed.

    Before you can do this you need to understand that a bond is due to a pair of electrons shared between atoms.

    When asked to draw a mechanism, curved arrows should be used to show all the bonding changes that occur.

    A few simple lessons

    Lesson 1


    Lesson 2


    Lesson 3


    Lesson 4


    Curved Arrow Summary curlyarrow.gif

    • Curved arrows curlyarrow.gif flow from electron rich to electron poor.
    • Therefore they start from lone pairs or bonds.
    • The charges in any particular step should always be balanced.
    • Remember to obey the rules of valence (eg. octet rule for C,N,O,F etc.)
    • If electrons are taken out of a bond, then that bond is broken.
    • If electrons are placed between two atoms then it implies a bond is being made.


    Draw curved arrows to indicate mechanisms for the following reactions:





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