Official Correct Choice:
Option A: n-pentane, 2-methyl butane, 2,2-dimethyl propane
Concept:Pentane (\( \text{C}_5\text{H}_{12} \)) has three structural chain isomers depending on how the five carbon atoms are connected.
Solution:- The three valid chain structures for five carbon atoms are:
- 1. A straight chain of 5 carbons: n-pentane.
- 2. A 4-carbon chain with one methyl branch on the second carbon: 2-methylbutane (isopentane).
- 3. A 3-carbon chain with two methyl branches on the central carbon: 2,2-dimethylpropane (neopentane).
- Note: Options A and D are identical in the source text. Marking A is standard.
Why other options are incorrect:Options B and C list "2,2-dimethylbutane", which contains 6 carbons total (hexane isomer), not 5. Also, "3-methylbutane" is just an incorrect numbering of 2-methylbutane.
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