How many pi and sigma bonds are in caffeine?

1 Answer
Truong-Son N.
Feb 21, 2016

Caffeine has the following structure:

![https://upload.wikimedia.org/](useruploads.socratic.org)

Suppose the molecule only had single bonds. That is, suppose we drew the skeletal structure, with no double bonds whatsoever. We can count each single bond in that case as one sigma bond.

That means there are these sigma bonds, followed by the count in parentheses:

  • "N"-"C" (3; "N"-"CH"_3 connection)
  • "C"-"N" (8; all in the rings)
  • "C"-"O" (2)
  • "C"-"C" (2)
  • "C"-"H" (10, from each "CH"_3 and one "C"-"H" between the "N"-"C"="N")

That's 3+8+2+2+10=25.

And now we count each double bond as having one sigma bond and one pi bond. Since we have already accounted for all sigma bonds, each double bond contributes one pi bond.

The number of pi bonds is therefore:

  • "C"="O" (2)
  • "C"="C" (1)
  • "C"="N" (1)

That's 2+1+1 = 4.

Hence, there are 25 sigma bonds and 4 pi bonds.

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