Figure 8 shows what the ethylene molecule looks like from an orbital perspective:
Figure 8.
The two CH bonds come from the sp2 + s orbitals and the double bond comes from the sp2 + Sp2 orbital set. This leaves two 2p orbitals that have a single electron each. They overlap to form a pi-bond which, together with the C-C bond will make a double bond. This pi-bond is also seen in figure 8. As you know, carbon can form triple bonds with itself, using a similar pattern to make acetylene (C2H2). In such cases, the ground state gets promoted as in the case of ethylene but hybridizes to make 2 sp hybrid orbitals and has two remaining 2p orbitals. These 2p orbitals will connect with the 2p orbitals on the opposite carbon atom two make 2 pi-bonds along with the C-C bond it already makes. This leads to a triple bond and a bond left over for a hydrogen atom on each side. The tight bonding makes for a shorter carbon-carbon bond length and a higher bond energy than is seen for single and double-bonded carbon structures like ethane and ethylene.
WRITING ORGANIC MOLECULAR STRUCTURES Hopefully, you now understand a little bit about how organic molecules bond and you understand the periodic table from previous chemistry courses. The good news is that 13
