Concept Explanation: Types of Structural Isomerism

The given image shows two molecules with the molecular formula C₄H₁₀O. These are butanol isomers. Let's analyze their structures to determine their relationship.

Step 1: Identify the Molecular Formula

Both molecules have the same molecular formula: C₄H₁₀O. This means they are isomers.

Step 2: Analyze the Functional Group

Both molecules contain an alcohol functional group (-OH). Therefore, they are functional group isomers of each other? No, because the functional group is the same. They must be a different type of isomer.

Step 3: Compare the Carbon Skeleton

Let's write their condensed structures:

Molecule 1: CH₃-CH₂-CH₂-CH₂-OH (Butan-1-ol)
Molecule 2: CH₃-CH(CH₃)-CH₂-OH (2-Methylpropan-1-ol)

Molecule 1 has a straight, unbranched chain of four carbon atoms. Molecule 2 has a branched chain; one carbon is attached as a methyl group to the second carbon. This difference in the arrangement of the carbon skeleton defines them as Chain Isomers.

Step 4: Eliminate Other Options

Metamers: These occur when alkyl groups attached to the same polyvalent functional group (like -O- in ethers, >C=O in ketones) are different. Both molecules are alcohols, not ethers or ketones, so this is incorrect.
Positional Isomers: These have the same carbon skeleton and functional group, but the functional group is attached to different carbon atoms. Here, the carbon skeleton itself is different (straight vs. branched), not just the position of the -OH group. The -OH group is on the terminal (1st) carbon in both cases.
Conformers: These are different spatial arrangements of the same molecule obtained by rotation around a single bond. These two structures are completely different molecules, not different conformations of the same molecule.

Final Answer

The two molecules are Chain Isomers.

Related Topics & Formulae

Types of Structural Isomerism

Structural isomers have the same molecular formula but different connectivity of atoms.

Chain Isomerism: Difference in the branching of the carbon skeleton.
Example: C₅H₁₂ (Pentane, Isopentane, Neopentane)
Positional Isomerism: Same carbon skeleton and functional group, but the functional group is in a different position.
Example: C₃H₇Cl (1-Chloropropane and 2-Chloropropane)
Functional Group Isomerism: Different functional groups.
Example: C₂H₆O (Ethanol, CH₃CH₂OH and Dimethyl ether, CH₃OCH₃)
Metamerism: A type of isomerism where different alkyl groups are attached to the same polyvalent functional group. Common in ethers and secondary amines.
Example: C₄H₁₀O (Methoxypropane, CH₃OC₃H₇ and Ethoxyethane, C₂H₅OC₂H₅)

Key Theory

Isomerism is a fundamental concept in organic chemistry that explains the diversity of organic compounds. The ability to identify the type of isomerism relies on carefully comparing the bonding sequence and functional groups between molecules that share the same molecular formula.