Question

Give IUPAC names for the following compounds:

Short answer

3-propyl-penta-1,3-diene.

Step-by-step solution

IUPAC (International Union for Pure and applied Chemistry)

IUPAC is an International body that represents chemistry and science. Its aim is to unite science globally. IUPAC devised a system of naming various chemical compounds systematically which is acceptable all over the world. It is constituted by 4 parts,

IUPAC name$\mathbf{=}\mathbf{Locant}\mathbf{+}\mathbf{Prefix}\mathbf{+}\mathbf{Parent}\mathbf{+}\mathbf{Suffix}$

Locant tells us the position of the substituent, prefix tell us what the substituent is, parent suggest the length of the carbon chain (2,3,4 and so on) and the primary functional group is identified by the suffix part.

There are some rules that must be followed in order to start naming a compound which you’ll get to understand as we deal with the question.

Numbering of the given compound

First we look for the longest parent chain of carbon that must contain maximum number of double bonds present in the molecule, in our case it is 5 carbon chain (pent) containing both the double bonds.

Now, start numbering carbon atoms from the side where double bond is near, in the given compound as multiple bond should get lowest number while numbering, so, we will start numbering from the right end (double bond will fall at position 1). There is a propyl group at position 3.

Naming of the given compound

Following, IUPAC name $\mathbf{=}\mathbf{Locant}\mathbf{+}\mathbf{Prefix}\mathbf{+}\mathbf{Parent}\mathbf{+}\mathbf{Suffix}$rule,

Remember to use di, tri etc before the substituents ( if more than one of same kind)or double bonds to indicate their number and to use numbers to indicate their location while naming compounds.

The name of the compound is3-propyl-penta-1,3-diene.