Alcohol Classification Lab

Oxidation behavior with Acidified $K_2Cr_2O_7$

Reaction: $Cr_2O_7^{2-} \text{ (Orange)} \rightarrow Cr^{3+} \text{ (Green)}$
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Lab Manual: Aim, Theory & Procedure
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Aim

To distinguish between primary, secondary, and tertiary alcohols using acidified Potassium Dichromate based on their oxidation behavior.

Principle

Primary: Oxidized to aldehydes and carboxylic acids (Orange $\rightarrow$ Green).
Secondary: Oxidized to ketones (Orange $\rightarrow$ Green).
Tertiary: Resistant to oxidation (Remains Orange) due to lack of $\alpha$-hydrogen.

$Cr_2O_7^{2-} + 14H^+ + 6e^- \rightarrow 2Cr^{3+} + 7H_2O$

Procedure

  1. Prepare Reagent: Add Dichromate and Acid to Tube 1, 2, and 3.
  2. Add Samples: Add Primary alcohol to Tube 1, Secondary to Tube 2, and Tertiary to Tube 3.
  3. Heating: Place tubes in the Water Bath at $70^\circ\text{C}$.
  4. Observe: Look for the orange-to-green color shift.

Reagent Bench

Dichromate
Acid
Primary
Secondary
Tertiary
TUBE 1
TUBE 2
TUBE 3

Heating Station ($70^\circ\text{C}$)

Observation Log

Tube Class Result

Logic Monitor

Add Acid and Dichromate to the tubes, then select the alcohols to test.

Ready