This post entails how to name alkenes and cycloalkenes in organic chemistry.
1 . Locate the C atoms in the longest C chain that contains the double bond. Use the
base name prefix with the ending -ene.
2. Number the C atoms of this chain sequentially beginning at the end nearer the
double bond. Insert the number describing the position of the double bond (indicated by its first carbon location) before the base name. (This is necessary only
for chains of four or more C atoms, because only one position is possible for a
double bond in a chain of two or three carbon atoms.)
3. In naming alkenes, the double bond takes positional precedence over substituents
on the carbon chain. The double bond is assigned the lowest possible number.
4. To name compounds with possible geometric isomers, consider the two largest
groups within the carbon chain that contains the double bond—these are indicated as part of the base name. The isomer in which the largest groups at each
end of the CUC are located on opposite sides is called trans. If the largest groups
are on the same side, the molecule is referred to as cis. Insert the prefix cis- or
trans- just before the number of the double bond to indicate whether the largest
groups are on the same or opposite sides, respectively, of the double bond.
5. For cycloalkenes, the double bond is assumed to be between C atoms 1 and 2,
so no position number is needed to describe it