Question

The IUPAC name of ${(C{H_3})_2}CHC{H_2}C{H_2}Br$ is:
 A. 1-Bromopentane
B. 2−Methyl−4−bromo pentane
C. 1-Bromo−3− methyl butane
D. 2-Methyl−3− bromo pentane

Answer 1

Hint:To find the IUPAC name of the above compound, firstly draw the structure of the compound. This will give the students a clearer idea to determine the name. Then start the numbering from the correct position. As a rule, the base part of the name mirrors the quantity of carbons in what you have allotted to be the parent chain. The suffix of the name reflects the type(s) of the functional group(s) present on (or inside) the parent chain. Different groups which are connected to the parent chain are called substituents.


Complete solution:
Firstly, select the parent carbon chain, then check the functional group, here in our question the functional group is bromine.
Then, Start naming the compound with that carbon. Now you can get 4 carbon atoms in your chain. Then start numbering the carbon atoms which are attached to bromine.
After writing the name of substituent along with position to which carbon it is attached and at last write suffix of functional group.
So, from the above discussion we can tell the name of the compound to be 1-bromo-3-methylbutane

Therefore,the correct option is (C).


Additional information:
Here are some rules to be kept in mind:
1) Identify the longest carbon chain (parent chain.)
2)Identify all of the substituents.
3) Start Numbering the carbons of the parent chain from the end which puts the substituents the lowest numbers.
4) If the same substituent occurs more than once, the position of the substituent is given.
5) If there are two or more different substituents, they are listed in alphabetical order using the base name. The only prefix which is used when putting the substituents in alphabetical order is iso as in isopropyl or isobutyl. The prefixes sec- and tert- are not used in determining alphabetical order except when compared with each other.
6)If there is equal length for the parent chain, then following rules shall be kept in mind:
a) the chain with maximum side chains is given more priority.
b) the chain where substituents have the lowest numbers.
c) the chain which has the greatest number of carbon atoms in the smaller side chain.
d) the chain which has least branched side chains.


Note:Students should keep in mind all the rules related to IUPAC nomenclature. Students usually make mistakes in numbering so they should number the positions very correctly. Also, students shall make the diagram very neatly so that they can easily name the compound without any difficulty.