Question

IUPAC name of chain isomer of butane is:
A.2-methyl butane
B.n-propane
C.Isobutane
D.Butane

Answer 1

Hint: If two molecules have the same molecular formula but different carbon in the main carbon chain, these are known as chain isomers. You already know that there are 4 carbons in butane’s main carbon chain. Now find the correct answer using these hints.

Complete step by step answer:
-As we already know chain isomers mean the compound has a difference in its carbon skeleton.
-There are 2 chain isomers of butane.
-The reason we call them both n-butane and isobutane is that they have 4 carbons. They aren’t the same compounds - different melting, boiling points, different chemical properties, etc.
$CH_{ 3 }CH_{ 2 }CH_{ 2 }CH_{ 3 }$
-The one above is n-butane - 4 carbons in a straight chain.
-The one below is iso-butane (also known as 2-methylpropane) - 3 carbons in a straight chain, and a branch.
$CH_{ 3 }CH(CH_{ 3 })CH_{ 3 }$
IUPAC name of this compound is isobutane.

Therefore, we can conclude that the correct answer to this question is option C.

Note: We can discuss other options also,
Option A, 2-methyl butane has a total five number of carbons so its molecular formula is different. Hence, it is not an isomer.
Option B, n-propane has a total three number of carbons so its molecular formula is different. Hence, it is not an isomer.
In IUPAC nomenclature butane is written as n-butane. (when it is not branched)