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Organic Chemistry - Some Basic Principles and Techniques
Structural Isomerism
1 question from 1 paper, each with its answer.
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- of Organic Chemistry - Some Basic Principles and Techniques
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Concepts tested
- Counting monochloro isomers by symmetry
All Questions
2004 AIPMT 1 question
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The molecular formula of diphenyl methane,
, is $C_{13}H_{12}$. How many structural isomers are possible when one of the hydrogens is replaced by a chlorine atom :-Diphenylmethane is symmetrical: the two phenyl rings are equivalent, and each ring is symmetrical about the axis through the $CH_2$ carbon and the para carbon.
So the distinct types of hydrogen are:
1. The two H atoms of the $CH_2$ group: replacing one gives $C_6H_5-CHCl-C_6H_5$.
2. Ortho H of a ring (2 per ring, all equivalent): gives o-chlorodiphenylmethane.
3. Meta H of a ring: gives m-chlorodiphenylmethane.
4. Para H of a ring: gives p-chlorodiphenylmethane.
(Substituting in the second ring gives the same compounds, because both rings are equivalent.)
So 4 structural isomers are possible.