1. DIFFERENCES IN REACTION RATES
OF THE OXIDATION OF DIFFERENT ALCOHOLS

The objective of the experiment is to examine the kinetics of the oxidation of methanol, ethanol, propan-1-ol and propan-2-ol with potassium dichromate in acidic solution using the Spektra^TM spectrometer.

Hazards

	Potassium dichromate is very toxic and dangerous to the environment. It is harmful in contact with skin and may cause sensitization by skin contact. It is toxic if swallowed. Wear protective gloves and goggles and avoid release to the environment. R: 49-46-21-25-26-37/38-41-43-50/53 S: 53-45-60-61
	Sulphuric acid is corrosive and causes severe burns. Wear suitable protective clothing, gloves and eye protection. R: 35   S: 26-30-36/37/39-45
	Methanol is flammable and toxic. Inhalation may cause cough, dizziness, headache, nausea, weakness and visual disturbance. It may be absorbed through skin and may cause redness and dry skin. Wear protective gloves. R: 11-23/24/25-39/23/24/25   S: (1/2-)7-16-36/37-45
	Ethanol is highly flammable. Inhalation may cause cough, headache, fatigue and drowsiness. It causes dry skin and redness of eyes. Wear protective gloves and goggles.   R: 11   S: (2-)7-16
	Propan-1-ol is irritating and highly flammable. Inhalation may cause ataxia, confusion, dizziness, drowsiness, headache, nausea and weakness. It can cause dry skin, redness of eyes, pain and blurred vision. Wear protective gloves and goggles.  R: 11-41-67   S: (2-)7-16-24-26-39
	Propan-2-ol is irritating and highly flammable. Inhalation may cause cough, dizziness, drowsiness, headache and sore throat. It may cause dry skin and redness of eyes. Wear protective gloves and goggles. R: 11-36-67   S:  (2-)7-16-24/25-26

The solutions of potassium dichromate (0.25 mol/L), sulphuric acid (4 mol/L) and solutions of methanol, ethanol, propan-1-ol and propan-2-ol (2.25 mol/L) are needed for the experiment. For the experiment all mentioned solutions and deionised water have to be in equal ten millilitre dropping bottles. In each experiment three drops of the solution of the oxidising agent, are combined on a blister with three drops of selected alcohol and three drops of acid. In the blank solution, alcohol is replaced with deionised water.

Measurements are performed with the red LED. Transmittance of the blank solution is set to 100.0. Measurements are started when the acid is added to the mixture of the oxidising agent and an alcohol. Measurements are recorded every 30 seconds.

Calculate the absorbance and present the results on the graph.

Explanation

The reaction runs the fastest with propan-1-ol and the slowest with methanol. It is possible to observe the  impact of alkyl radical length on the oxidation rate. The longer the alkyl radical, the faster the oxidation. Could this rule  be generalized? What is the effect of radical branching on the reaction rate?

Developed and prepared by: Nataša Gros, University of Ljubljana, Faculty of Chemistry and Chemical Technology and Margareta Vrtačnik, University of Ljubljana, Faculty of Natural Sciences and Engineering