Question

Which of the following is the incorrect IUPAC name of a compound?
A. Pent-3-ene
B. Prop-1-en-2-yne
C. 1-methylpropane
D. All are incorrect.

Answer 1

Hint: The IUPAC system is the most widely used system of naming in organic chemistry and the most important feature of this system is that for any given molecular structure there exists one IUPAC name.

Complete step by step answer:
To find the incorrect IUPAC name of a compound, we have to draw the structure of all the given compounds. If we talk about option A i.e. pent -3-ene, as per the structure drawn below, there are five carbon chain and the position of the double bond is located on the third carbon:

But according to the IUPAC rule, the numbering of parent chains is done from that side in which a double bond gets the lowest position. According to the IUPAC rule, its naming should be pent-2-ene which is given as:

Hence option A is wrong.
In the case of option B, the structure of Prop-1-en-2-yne drawn below is not possible because the valency of carbon is four i.e. carbon makes maximum foy=ur bond but here five bonds are formed by carbon. Hence it is also wrong.:

In the case of option C, 1-methylpropane, the structure is given below:

According to IUPAC the name of the above compound should be butane which is given as:

Hence option C is also incorrect.

So, the correct answer is Option D.

Note: The IUPAC name of any organic compound contains three parts:
1. Word root which indicates the number of carbon atoms in the parent chain. Thus it is the basic unit of the name.
2. Suffix: There are two types of a suffix such as primary and secondary suffix. Primary suffix indicates carbon is saturated or unsaturated whereas the secondary suffix indicates the nature of the functional group.
3. The prefix is also two types such as primary as well as a secondary prefix. Primary prefix distinguishes cyclic or acyclic compounds whereas secondary prefix indicates a functional group which is treated as a substitute.