Concept:Position isomers share the exact same carbon skeleton and the same functional groups, but differ solely in the location (position) of those functional groups on the chain.
Solution:- Propylene glycol is the common name for 1,2-propanediol (\( \text{CH}_3\text{-CH(OH)-CH}_2\text{OH} \)). The hydroxyl groups are on adjacent carbons.
- Trimethylene glycol is the common name for 1,3-propanediol (\( \text{HO-CH}_2\text{-CH}_2\text{-CH}_2\text{-OH} \)). The hydroxyl groups are at the ends of the chain.
- Since the only difference is the placement of the \( \text{-OH} \) groups on the 3-carbon chain, they are position isomers.
Why other options are incorrect:They both contain alcohol functional groups (not functional isomers). Metamerism does not apply as the alkyl chain isn't split by a central functional group. They do not interconvert dynamically (not tautomers).
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