Propane is a gas derived from fossil fuel and is used for cooking and heating. Analysis shows it is made completely of carbon and hydrogen; its basic formula is C3H8.
Carbon can bind to other carbons and in propane the three carbons are bound to each other, one after the other. In addition, each carbon must have four bonds total, so the hydrogens are bound to each carbon in propane to complete the four bond requirement. This results in three hydrogens bound to each of the end carbons, and two hydrogens bound to the middle carbon. This structure can be represented by drawing straight lines and 90 degree angles between all atoms (Figure 1).
The actual angle between all bound atoms is 109.5 degrees and three dimensional representations of propane include a zig-zag structure (Figure 2).
Molecules in three-dimension are in constant motion and atoms connected by a single bond can potentially rotate unrestricted about that bond.
Since atoms are charged, repulsions must be considered. The best energy position has hydrogen atoms staggered on different carbons .
Not all hydrogens are chemically equivalent; the two hydrogens on carbon two are in a different environment than those on carbons one and three. Hydrogens on carbon two are more reactive.