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Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol ?

Chemistry
WAEC 2019

Which of the following reagents could be used to distinguish between propan-1-ol and propan-2-ol ?

  • A. H+ / K2Cr2O7
  • B. I\(_2\) / OH\(^-\)
  • C. CH\(_3\)COOH
  • D. NaCl
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Correct Answer: Option B
Explanation

The reagent I\(_2\) / OH\(^-\) (iodine in alkaline solution) is used for the iodoform test, which identifies compounds containing a methyl ketone group or a methyl hydroxy group (specifically a secondary alcohol with the structure CH\(_3\)CH(OH)R). 

Propan-2-ol is a secondary alcohol (CH\(_3\)CH(OH)CH\(_3\)) that possesses the required methyl group adjacent to the hydroxyl-bearing carbon. It reacts with I\(_2\) / OH\(^-\) to produce a characteristic yellow precipitate of iodoform (CHI\(_3\).

Propan-1-ol is a primary alcohol (CH\(_3\)CH\(_2\)CH\(_2\)OH) and does not have this specific structure. Consequently, it gives a negative result (no yellow precipitate)


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