Removing a hydrogen from an alkane results in an alkyl substituent (or an alkyl group). Alkyl substituents are named by replacing the “ane” ending of the alkane with “yl.” The letter “R” is used to indicate any alkyl group.
Isopropyl group—contain three carbon atoms. A propyl group is obtained when a hydrogen is removed from a primary carbon of propane.
The prefix "iso" is used when all carbons except one form a continuous chain. This one carbon is part of an isopropyl group at the end of the chain.

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Common name: isopentane
IUPAC name: 2-methylbutane |
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Common name: isopentyl alcohol
IUPAC name: 3-methyl-1-butanol |