Given below are two statements: Statement (I):
are isomeric compounds. Statement (II):
are functional group isomers. In the light of the above statements, choose the correct answer from the options given below:
Both Statement I and Statement II are true
Statement I is false but Statement II is true
Statement I is true but Statement II is false
Both Statement I and Statement II are false
Correct answer:D
Standard Method
Given: Two statements about isomerism and functional group isomerism are to be checked.
Find: Which option correctly describes the truth values of Statement (I) and Statement (II).
For Statement (I), the two compounds are methylcyclobutane and pentane.
Their molecular formulae are:
Since isomeric compounds must have the same molecular formula, these two compounds cannot be isomers. Therefore, Statement (I) is false.
For Statement (II), one compound contains an amine group and the other contains an amide group. Functional group isomers must have the same molecular formula but different functional groups.
Here, the number of atoms in the two compounds is not the same, so they are not functional group isomers. Therefore, Statement (II) is false.
Hence, both Statement I and Statement II are false.
The correct option is D.
Statement-wise Analysis
Given:
Find: The correct option.
Statement (I): For compounds to be isomers, they must have the same molecular formula but different structures or configurations. On comparing the pair shown, their molecular formulae are different, so the basic condition for isomerism is not satisfied.
Statement (II): Functional group isomerism requires the same molecular formula with different functional groups. Although the functional groups shown are different, the molecular formula condition is not satisfied here either.
Therefore, neither statement satisfies the required criteria.
So, both Statement I and Statement II are false, and the correct option is D.
Students often check only whether the structures look different. Different structures alone do not make compounds isomers; they must also have the same molecular formula. Always compare molecular formula first.
A common mistake is to think any two compounds with different functional groups are functional group isomers. This is wrong because functional group isomerism requires both same molecular formula and different functional groups.
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