Question

Draw the structure of 3-methylpent-2-ene.

Answer 1

Hint:We are given an IUPAC name of the compound. The method of naming organic compounds is known as the IUPAC nomenclature. In the given name, suffix –ene is written thus, a double bond must be present.

Complete answer
We are given an IUPAC name of the compound i.e. 3-methylpent-2-ene.
pent- means that the parent alkane is pentane. Pentane means there are five carbon atoms present.
3-methyl means there is a methyl $\left( { - {\text{C}}{{\text{H}}_3}} \right)$ group attached to the third carbon of the parent alkane. pent-2-ene means there is a double bond to the second carbon.

Thus, the structure of 3-methylpent-2-ene is as follows:

In the structure, we can see that there are five carbon atoms, the methyl group is attached to the third carbon and the double bond is attached to the second carbon.

Note:The rules for writing IUPAC name of alkenes are as follows:
i) Select the longest continuous chain of carbon atoms containing carbon-carbon double bonds in the structure of the molecule.
ii) Number the carbon atoms in the selected carbon chain from the end which is nearest to the double bond.
iii) Count the number of carbon atoms in the chain. This is the parent alkane.
iv) The name of alkene is written by replacing suffix ‘ane’ in the parent alkane by ‘ene’
v) Write the number indicating the position of the double position before prefix ‘ene’.
vi) Assign a number to each substituent according to the carbon atom it is attached. If there are two substituents on the same carbon, assign the same number to them.