Chemistry Alcohols & Phenols MDCAT 2014
PMDC Verified Question 86 of 95
Which one of the following groups is indicated when HCl is formed by reaction of ethanol with phosphorus pentachloride?
A
Amino group
B
Halide group
C
Hydroxyl group
D
Hydride group
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: Hydroxyl group
Concept:

Phosphorus pentachloride (\(\text{PCl}_5\)) is a standard analytical reagent used to confirm the presence of a hydroxyl (-OH) group in organic compounds.

Formula:

$$ \text{R-OH} + \text{PCl}_5 \longrightarrow \text{R-Cl} + \text{POCl}_3 + \text{HCl} $$

Solution:

  • The violent evolution of hydrogen chloride (HCl) gas fumes when an organic compound is treated with \(\text{PCl}_5\) definitively proves the compound contains an -OH group.


Why other options are incorrect:

Amino, halide, and hydride groups do not produce HCl gas upon reaction with \(\text{PCl}_5\) via this specific substitution mechanism.

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