Question 26.SE.4: Name the following compounds:
Name the following compounds:
(a) 
(b) 
Analyse We are given the structural formulas for two compounds— the first an alkene and the second an alkyne—and asked to name them.
Plan In each case, the name is based on the number of carbon atoms in the longest continuous carbon chain that contains the multiple bond. In the case of (a), care must be taken to indicate whether E, Z isomerism is possible and, if so, which isomer is given.
Solve
(a) The longest continuous chain of carbons that contains the double bond is seven carbons in length. The parent compound is therefore heptene. Because the double bond begins at carbon 2 (numbering from the end closest to the double bond), the parent hydrocarbon chain is named hept-2- ene. A methyl group is located at carbon atom 4. Thus the compound is 4-methylhept-2-ene. The geometrical configuration at the double bond is Z (that is, the alkyl groups are bonded to the double bond on the same side). Thus the full name is Z-4-methylhept-2-ene.
(b) The longest continuous chain of carbon atoms containing the triple bond is six, so this compound is a derivative of hexyne. The triple bond comes after the first carbon (numbering from the right), making it a derivative of hex-1-yne. The branch from the hexyne chain contains three carbon atoms, making it a propyl group. Because it is located on the third carbon atom of the hexyne chain, the molecule is 3-propylhex-1-yne.