Question

The IUPAC name of the following compound is 2-methylbicyclo [3.1.1] heptane.

A.True
B.False

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 solution: The set of rules set up by IUPAC are as follows:
1.We first need to identify the longest carbon chain which is called the parent chain.
2.Then we need to find all the substituent which are the groups appending from the parent chain.
3.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.
4.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.
5.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.
6.If there are equal lengths for parent chain, the we need to select the parent chain according to these rules:
a.The chain that has the greatest number of side chains.
b.The chain which has the lowest number on its substituents.
c. The chain that has the greatest number of carbon atoms in its smaller side chain.
d.The chain that has the least branched side chains.
7.While naming a cyclic (ring) hydrocarbon we used the prefix cyclo- which appears directly in front of the base name.
8.If there are more than 1 cyclic ring then we start the numbering with the ring that has more number of carbon atoms. If there are two cyclic rings, then the term bicyclo is used for them.
9.Also, in compounds with two cyclic rings, the name bicyclo is always followed by the number of carbon atoms between the two fixed carbon atoms, in descending order. The two bridged-carbon atoms are also included in the numbering.

Now, let us name the compound given to us according to IUPAC.

First let us number the longest carbon chain. It contains 6 carbon atoms, and they are numbered from 1 to 6.

Now, the numbering of the second longest chain is done in continuation with the longest chain.

Now, we can see that a methyl group is attached to the ${2}^{nd}$ carbon atom. Therefore, the name of this compound starts as 2-methyl. Now, since it is a bicyclic compound, we add the name bicyclo after methyl and it is given that bicyclo is followed by the number of carbon atoms between the two fixed carbon atoms, in descending order. So that becomes, 2-methylbicyclo[3.1.1]. And finally followed by the alkane. So, the IUPAC name of the given compound is 2-methylbicyclo [3.1.1] heptane. Therefore, the IUPAC name of the compound given in the question is correct. Hence, the correct answer is option (A).

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.
Students often get confused while numbering the bicyclic compounds. We write the number of carbon atoms which are between the two fixed or we can say the bridged carbon atoms followed by the bicyclo name. Note that these numbers of carbon atoms are written in descending order.