Step 1: Identify the structure of the molecule CH3-CH2-CHO. It has a chain of carbon atoms with a functional group at the end.
Step 2: Count the number of carbon atoms in the longest chain. There are 2 carbon atoms (CH3 and CH2).
Step 3: Recognize that the functional group 'CHO' is an aldehyde, which is characterized by the presence of a carbonyl group (C=O) at the end of the carbon chain.
Step 4: The name of the aldehyde with 2 carbon atoms is 'acetaldehyde'.
Step 5: Combine the information to conclude that the IUPAC name for CH3-CH2-CHO is acetaldehyde.
