How many sigma bonds are present in caffeine?
Caffeine has a total of 25 sigma bonds.
Here's how caffeine's Lewis structure looks like:
Every line represents a sigma bond, while every double bond, represented by two parralel lines, numbers one sigma and one pi bond. After analyzing the structure, you should come to the conclusion that the caffeine molecule has 25 sigma bonds.
Here's another representation of the molecule's Lewis structure; this time, all the bonds are drawn and thus easier to spot
As a side note, the caffeine molecule also has 4 pi bonds, one for every double bond present.