Is isomeric with CH3CH2CHO — Bonding Chemistry Question

STEPS:

1. Understand the Concept of Isomerism: Isomers are molecules that share the same molecular formula (the same number and type of each atom) but have different structural arrangements of those atoms.
2. Determine the Molecular Formula of the Target Compound: The given molecule is $CH_3CH_2CHO$ (propanal). Counting the atoms shows it contains:
* 3 Carbon atoms
* 6 Hydrogen atoms
* 1 Oxygen atom
* Molecular Formula: $C_3H_6O$
3. Evaluate the Molecular Formula of Choice C: $CH_3COCH_3$ (propanone or acetone) contains:
* 3 Carbon atoms
* 6 Hydrogen atoms (3 + 3)
* 1 Oxygen atom
* Molecular Formula: $C_3H_6O$
4. Confirm the Isomeric Relationship: Because $CH_3CH_2CHO$ and $CH_3COCH_3$ have the exact same molecular formula but different functional groups (one is an aldehyde, the other is a ketone), they are functional isomers.
5. Conclusion: Choice C is the correct answer as it is the only option that contains the exact same number of atoms as the target molecule.

WHY_OTHERS_WRONG:

• $CH_3CH_2CH_2CH_3$ (A): This is butane, an alkane. It has a molecular formula of $C_4H_{10}$, which has too many carbons and hydrogens and lacks an oxygen atom.
• $CH_3CH_2CH_2OH$ (B): This is propan^-1-ol, an alcohol. Its molecular formula is $C_3H_8O$. While it has the correct number of carbons and oxygens, it has two extra hydrogen atoms, making it non-isomeric with the target.
• $CH_3COOH$ (D): This is ethanoic (acetic) acid. Its molecular formula is $C_2H_4O_2$, meaning it has too few carbons and an extra oxygen atom.
• $CH_3CH_2CH_2NH_2$ (E): This is propan^-1-amine. Its formula is $C_3H_9N$; it contains a nitrogen atom, which is not present in the target molecule.