Alkenes

Every alkene contains at least one C=C double bond — this is the functional group that gives alkenes their characteristic chemistry. Alkanes (single C-C bonds only) are relatively unreactive because their bonds are strong and non-polar. Alkenes, on the other hand, are reactive precisely because of that double bond.

Think of the double bond like a loaded spring sitting inside the molecule — full of energy (electron density) and just waiting for something to come along and react with it.

They're called unsaturated hydrocarbons because:

• They contain carbon-carbon double bonds (not "saturated" with the maximum possible hydrogens)
• They're made of hydrogen and carbon atoms only

Naming Alkenes

Alkenes are named with the suffix -ene (alk + ene). For chains of 4 or more carbons, you must number the chain (starting from the end closest to the double bond) and state the position of the double bond using the lower-numbered carbon involved.

This is the concept that everything else in the chapter hangs off, so let's really slow down here.

4 outer-shell electrons double 4 electrons total two different kinds of bond

σ (Sigma) Bonds — the "head-on" bond

end-to-end

three

π (Pi) Bonds — the "sideways" bond

p orbital sideways