Question

The IUPAC name of ($CH_3-CH_2-CHO$) is:

• A. Propanone
• B. Propanal
• C. Propanoic acid
• D. Ethanol

Hint:

Draw out the full structure of $CH_3-CH_2-CHO$ first and count every carbon in the main chain, including the carbon that is part of the CHO group itself, since that carbon is always counted as carbon number one for this functional group. Once the chain length and the position of the functional group are fixed, the correct suffix follows directly from the standard IUPAC naming rules for this group. Watch out for options describing a different functional group entirely, like an alcohol or a ketone, since those are easy traps if the group in the structure is misread.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
IUPAC nomenclature follows a specific set of rules: identifying the longest carbon chain, the functional group, and the appropriate suffix.

Step 2: Detailed Explanation:
1. Count the Carbons: The chain $CH_3-CH_2-CHO$ has 3 carbon atoms. The prefix for 3 carbons is "prop-". 2. Identify the Bond: It is a saturated chain (single bonds between carbons), so it is "propan-". 3. Identify the Functional Group: The group $-CHO$ is an aldehyde. 4. Determine the Suffix: The IUPAC suffix for aldehydes is "-al".

Step 3: Final Answer:
Combining these, we get Propanal. (Propanone is a ketone, Propanoic acid is a carboxylic acid).

Answer 2

Concept:

• Instead of building the name step by step, test each option against the structure directly and eliminate the ones that belong to a different class of compound entirely.

Step 1: Identify the functional group in the given compound.
$CH_3-CH_2-CHO$ ends in a $-CHO$ group, which sits at the end of the chain. A group at the very end of the chain is always an aldehyde, never a ketone.

Step 2: Rule out "Propanone".
Propanone (acetone) is a ketone, which needs the carbonyl group INSIDE the chain, not at the end. The carbonyl in this compound sits at the very end, so this option is wrong.

Step 3: Rule out "Propanoic acid" and "Ethanol".
Propanoic acid would need a $-COOH$ group (two oxygens), but we only have one. Ethanol is an alcohol with just 2 carbons and no carbonyl at all. Both are wrong.

Step 4: Confirm the remaining option.
$-CHO$ on a 3-carbon chain is exactly what "propanal" describes ("propan" for 3 carbons, "-al" for aldehyde).

Final Answer: Propanal