Question

Indicate the wrongly named compound.
A.

B.

C.

D.

Answer 1

Hint: The naming of the compound is done according to the IUPAC set of rules. These rules are must to follow for the correct naming of the compound.

Complete step by step answer:
The set of rules set up by IUPAC are as follows:
We first need to identify the longest carbon chain which is called the parent chain.
Then we need to find all the substituent which are the groups appending from the parent chain.
We need to number the carbon atoms of the parent chain from that end of the chain which gives the lowest number to the substituent. If we counter two or more side chains that are equivalent in positions, then we assign the lowest number to the one which will come first in the name.
If the same substituent group occurs more than once, then the location of each point on which it occurs is given. And in addition, we have to mention the number of times that substituent group has occurred, indicated by prefixes like di, tri, tetra, etc.
If two or more substituent groups are present then they are named in alphabetical order using their base name. The only prefix that we have to use while putting the substituents in alphabetical order is iso like isopropyl or isobutyl. We do not use the prefixes sec- and tert- in determining the alphabetical order except when compared with each other.
If there are equal lengths for parent chain, the we need to select the parent chain according to these rules:
The chain that has the greatest number of side chains.
The chain which has the lowest number on its substituents.
The chain that has the greatest number of carbon atoms in its smaller side chain.
The chain that has the least branched side chains.
While naming a cyclic (ring) hydrocarbon we used the prefix cyclo- which appears directly in front of the base name.

Let us now see the names of the given compounds.

The IUPAC name of this compound is 4-methylpentan-1-al.

The IUPAC name of this compound is 4-methylpent-2-ene-1-oic acid.

The IUPAC name of this compound is 2-methyl-1-pentanoic acid.

The IUPAC name of this compound is hex-3-en-2-one.

Now, by comparing the IUPAC names of these compounds with the names given in the question, we can see that option (d) was named incorrectly. Hence, option (d) is the correct option.

Note: The IUPAC naming of the compounds is followed worldwide. It establishes a standard way of naming the compounds so that there is no confusion regarding the compounds in the world of chemistry.