How To Draw Organic Chemistry Molecules

Posted on July 30th, 2012

  1. Learning organic chemistry is like learning a new language. With a new language comes a new way of speaking and a new way of writing. In organic chemistry we communicate with lines and letters.
  2. How to draw bonds
      1. Bonds are represented by lines. One line is a single bond, two lines is a double bond and three lines is a triple bond
        Bond Drawing
        Single
        Double
        Triple
      1. Bonds may be in a variety of different planes
        Drawing Representation
         Drawn to represent a bond within same plane as the computer screen or paper
         Drawn to represent a bond coming out of the plane of the computer screen or paper. In essence this bond is pointing toward you.
         Drawn to represent a bond going into the plane of the computer screen or paper. In essence this bond is pointing away from you.
  3. General rules of drawing in orgo using the “Line-Angle Formula”
    1. General Rule #1:
      1. Anytime there is a line drawn, the atom at each end is a carbon unless otherwise indicated.
      2. The appropriate number of hydrogens are attached to it and implied even though they may not be drawn
      3. For example, each of these three are equivalent depictions of the same compound:
        Condensed Formula Conventional Structure Drawing Line-Angle Formula Drawing
        CH3CH3

        Looking at this Line-Angle Formula drawing we see a line. Each end of the line has a carbon. Since the carbons are connected by a single bond, each carbon has three hydrogens attached to it.

    2. General Rule #2:
        1. Each carbon molecule may accommodate four “things” attached to it via a single bond. If there is a double bond that counts as two “things” if there is a triple bond that counts as three “things”
        2. So what about this molecule:

      Letís start by circling all the lines:

      Well, there are three lines, right? Each positioned at an angle to one another to indicate that there is a new carbon at that joint.
      So the following two images are equivalent:

      Conventional Structure Drawing Line-Angle Formula Drawing

For practice on this subject try out our exercise set at:

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