Drawing Tetraheral Structures on Computer

We learn about the tetrahedral geometry of methane because the same tetrahedral geometry is important in many other molecules.  sp3 systems are very common and many have handedness or are chiral.  You need to master drawing interconnected tetrahedrons for larger molecules and to draw this handedness efficiently.  In this example, we will draw (S)-butan-2-ol.  Don't worry if you don't know what this molecule is or understand its name yet...we will learn this soon enough.

(S)-butan-2-ol

Take NoteIt's often convenient to draw straight-chain molecules such that all the C atoms are in the same plane of the canvas.
Action
  • Examine the structure above - the dashed wedge showing the OH (behind) the canvas and the H in front of the plane of the canvas.  The canvas is in the plane of your computer screen.
  • Hover over the structure of (S)-butanol and show the hydrogens.  DON'T FORGET ABOUT THE IMPLIED HYDROGENS!
Action
  • Draw (S)-butan-2-ol in the applet below.  Armed with my knowledge that 3 atoms of a given tetrahedron should be in the same plane, draw all 4 carbons as a zigzag line all in the plane of the drawing canvas.
  • Use a dashed wedge to show the OH projecting away from the canvas plane.
  • Use a solid wedge to show the H projecting toward you.
  • Note that the wedges have a small and large end.  The small ends ALWAYS connected to the atom in the plane.

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