Question

The number of isomeric forms that are represented by C7H9N is:

• A. 5
• B. 2
• C. 6
• D. 9

Answer 1

The Correct Option is A

To determine the number of isomeric forms represented by the molecular formula C₇H₉N, we need to identify the possible structures that can be formed using these atoms. The formula suggests it is an aromatic compound containing one nitrogen atom, which is typically seen in aniline derivatives (aromatic amines) or other nitrogen-containing ring structures.

Here’s a step-by-step breakdown:

1. The molecular formula C₇H₉N suggests a common structure is one of an aminotoluene (i.e., methyl aniline). The benzene ring (C₆H₅) allows for multiple substitution patterns with an alkyl group (CH₃) and an amino group (NH₂).
2. There are three possible positional isomers of methyl group substitution relative to the amino group on the benzene ring:
   • Ortho (o-) position (adjacent to each other)
   • Meta (m-) position (one carbon apart)
   • Para (p-) position (opposite each other)
3. Additionally, the nitrogen could be part of a nitrogen-containing heterocycle like azepine, which can have its own isomers or derivates.
4. Therefore, by considering all relevant structural possibilities, we conclude that there are a total of 5 isomeric forms that can exist with the molecular formula C₇H₉N. These include:
   • o-Toluidine
   • m-Toluidine
   • p-Toluidine
   • Heterocyclic compound e.g., azepine derivatives
   • Possible other aromatic amine configurations

The correct answer is, therefore, 5.

Options like 2, 6, and 9 can be ruled out as they do not cover all plausible isomeric variations for this formula. The main reasoning involves the analysis of substitution patterns around the benzene ring and possible nitrogen arrangements.