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Double Bonds

    A double bond is a bond between two elements that requires 2 pairs of elections rather than 1. It is shorter and stronger than a single bond. The most common double bond appears between two carbon atoms.

    Double Bond.JPG

    Since the the two atoms are connected by two bonds, it makes them incapable of rotating.

    Introduction

    Double bonds are stronger than single bonds because there are two bonds instead of one. They are also shorter because the bonds bend a bit but single bonds stay straight. Since there are two bonds connecting two atoms, they cannot rotate.

    Orbital Hybridization

    When two atoms with three sp2 orbitals  approach each other, two of their sp2 orbitals overlap, forming a sigma bond. On the other hand, their two p-orbitals form a pi bond. Since they want to be overlapped to the maximum, the sp2 orbitals stay parralell to each other. Therefore, the two atoms connected by a double bond cannot rotate.

    Questions:

    1. Why can't atoms connected by a double bond rotate?

    2. Why is a double bond shorter than a single bond?

    3. Why are double bonds stronger than single bonds?

    References

    1. Chang, Raymond. Physical Chemistry for the Biosciences. CA: University Science Books, 2005.
    2. Housecroft, Catherine. Inorganic Chemistry. England: Pearson Education Limited, 2008.

    Contributors

    • Michael Dai

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