The Oxidation of Ethanol to Ethanoic Acid

Introduction

Oxidation, put simply, is a chemical reaction in which oxygen is added to a compound, creating a different compound. The reaction of ethene gas (produced form the dehydration of ethanol) with potassium manganate(VII) is an example of an oxidation reaction that produces an alcohol. Another example of oxidation is the reaction of sodium dichromate(VI) solution with ethanol to give a carboxylic acid, ethanoic acid, a dilute solution of which is sold as vinegar.

Diagram

Method

Into a boiling tube add about a cm depth of the sodium dichromate solution provided. Clamp the boiling tube so that the end of the tube is immersed in a beaker of cold water (see the diagram above). Add three or four small anti-bumping granules to the boiling tube. Then SLOWLY add dropwise an equal volume of ethanol to the boiling tube (using a dropping pipette). When the ethanol has been added, heat the beaker of water until a gentle boiling is produced in the boiling tube. Leave the boiling tube in the hot water for about twenty minutes, then remove the heat, and allow the boiling tube and its contents to cool down.

Note down all your observations during this reaction.

Tests on the product

(i) Smell the test tube at the end of the reaction (very carefully), and note any difference from the smell of ethanol (the starting material).

Using an authentic sample of ethanoic acid from a bottle do the following tests

(ii) To a cm depth of ethanoic acid, in a test tube, add a small amount of calcium carbonate and/or copper carbonate. Note all observations.

(iii) To a cm depth of ethanoic acid, in a boiling tube, add a small amount of copper oxide. Warm the mixture gently over a Bunsen burner flame. Note all observations.