Chemistry Alcohols & Phenols MDCAT 2014
PMDC Verified Question 85 of 95
Primary, secondary and tertiary alcohols can be identified and distinguished by
A
Lucas test
B
Bayer's test
C
Iodoform test
D
Silver mirror test
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Lucas test
Concept:

The Lucas test utilizes Lucas reagent (conc. HCl + anhydrous \(\text{ZnCl}_2\)) to differentiate alcohols based on their reactivity via the \(\text{S}_N1\) mechanism.

Formula:

$$ \text{R-OH} + \text{HCl} \xrightarrow{\text{ZnCl}_2} \text{R-Cl (oily layer)} + \text{H}_2\text{O} $$

Solution:

  • Tertiary alcohols react immediately to form a cloudy/oily layer.


  • Secondary alcohols take 5-10 minutes to react.


  • Primary alcohols do not react at room temperature (require heating).


Why other options are incorrect:

Baeyer's test identifies unsaturation (double/triple bonds). Iodoform test specifically identifies methyl ketones or methyl carbinols (like ethanol). Silver mirror test identifies aldehydes.

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