Solution:Concept- The compounds with ‘’ group are aldehydes and their name ends with ‘al’.
IUPAC rules for naming aldehydes are:
● The name of an aldehyde ends with “al”.
● Choose the longest carbon chain for the root name.
● Number the carbon atoms on this longest chain such that the carbon of - the group gets the lowest number.
● Identify the other substituents and their position.
● If the same substituent appears more than once, then the prefix (di, tri, tetra) is used to indicate their frequency.
● If there are more than 2 substituents, they are named in alphabetical order with the position written ahead of them.
Thus, using the above rules, the given compound is named propan-1-al as ‘prop’ represents 3 carbon atoms.
Hence, the correct option is (1).