Question

Which one of the following is \[1 - \]bromo\[ - 3 - \]methyl butane?
a. \[{\left( {C{H_3}} \right)_2}CHC{H_2}C{H_2}Br\]
b. \[{\left( {C{H_3}} \right)_2}C\left( {Br} \right)C{H_2}C{H_3}\]
c. \[{\left( {C{H_3}} \right)_2}CHCH\left( {Br} \right)C{H_3}\]
d. \[C{H_3}{\left( {C{H_2}} \right)_5}Br\]

Answer 1

Hint: As we know that the IUPAC nomenclature is a chemical nomenclature which is used for the naming of organic compounds by following some rules and regulations. And it is proposed by the International Union of Pure and Applied Chemistry. For solving an IUPAC name, first we have to identify the longest carbon chain present in the molecule and look if any functional is there or any branched chain is there or not. After that, conclude the name into a single word.

Complete answer:
According to IUPAC nomenclature, the name of \[{\left( {C{H_3}} \right)_2}CHC{H_2}C{H_2}Br\] is \[1 - \]bromo\[ - 3 - \]methyl butane.
Here, the parent hydrocarbon is identified as butane. Which means, the longest continuous chain of carbon atoms in the compound is carbon with four. Therefore, the name should contain butane. And one methyl group is attached to the third position of the compound. The carbon contains one bromine, hence the name should be started like‘\[1 - \]bromo’. And from the given structures, these rules apply only to \[{\left( {C{H_3}} \right)_2}CHCH\left( {Br} \right)C{H_3}\]. Hence, option (a) is correct.
The name of \[{\left( {C{H_3}} \right)_2}C\left( {Br} \right)C{H_2}C{H_3}\] is not \[1 - \] bromo \[ - 3 - \] methyl butane. Because, here the bromine is attached to the second carbon atom. Hence, option (b) is incorrect.
\[1 - \] bromo \[ - 3 - \] methyl butane is not the name of \[{\left( {C{H_3}} \right)_2}CHCH\left( {Br} \right)C{H_3}\]. Because, here one carbon contains two substituents. Hence, option (c) is incorrect.
The name of \[C{H_3}{\left( {C{H_2}} \right)_5}Br\] is not \[1 - \] bromo \[ - 3 - \] methyl butane. Because, here the number of carbon is not equal to four. Hence, option (d) is incorrect.
So, the correct answer is “Option a”.

Note:
 We need to know that the IUPAC nomenclature is used for the naming of organic compounds. For that, first we have to identify the longest continuous carbon chain present in the parent compound and find out the group linked to this longest chain. The name is different for each functional group. For example, if the acid group is present in the compound, the suffix should be ‘-oate’. Like that, we are naming an organic compound.