THE TECHNICAL UNIVERSITY OF KENYA
DEPARTMENT OF CHEMICAL SCIENCE AND TECHNOLOGY
Reactions of Alcohols
Introduction
Alcohols, also called alkanols, are compounds which contain carbon and hydrogen and a hydroxyl (OH)
group. The OH is the functional group. Alcohols may be classified into primary (R—CH2—OH), secondary
(R2—CH2—OH) and tertiary (R3—CH—OH).
Reactions of alcohols can be of two main types:
a) Reactions where the oxygen is lost e.g.
Substitution reaction: CH3CH2OH + X- → CH3CH2—X + OH-
Elimination reaction: CH3CH2—OH + Al2O3 → CH2=CH2 + H2O
b) Reactions where the oxygen is retained. e.g.
Primary and secondary alcohols can be oxidized by several methods to give aldehydes and ketones
respectively. (The aldehydes may further be oxidized to carboxylic acids under same conditions)
CH3CH2—OH + Na2CrO7/H2SO4 → CH3CHO
Primary Ethanal (Aldehyde)
(CH3)2—OH + Na2CrO7/H2SO4 → (CH3)2CO
Secondary alcohol Propanone (ketone)
c) Under strong conditions alcohols can be forced to act as acids:
CH3CH2—OH → CH3CH2—O- + H+
This reaction can be seen with sodium metal
CH3CH2—OH + Na → CH3CH2—O-Na+
Experimental Procedure
Carry out the following tests and record your observations and inferences in the spaces provided.
1. Reaction with Sodium metal
a) Put about 1.0 mL of the alcohol in a dry test-tube and add a small piece of sodium (rice grain
size). Test the gas evolved (if any) with a lighted splint
Observation Inference
b) When the sodium has all dissolved, carefully evaporate the solution to dryness and add 3 drops
of water. Test the solution with litmus paper.
Observation Inference
2. Reaction with carboxylic acids (esterification):
a) Warm a mixture of 5 drops of alcohol and 5 drops of ethanoic acid with 1 drop of concentrated
sulphuric acid (Care). Note the characteristic smell of the product.
Observation Inference
b) To 5 drops of an alcohol in a test-tube add 2-3 drops of acetyl chloride. Note the characteristic
smell of the product.
Observation Inference
3. Oxidation reactions:
a) Place 5 drops of the alcohol in a test-tube, add 10 drops of dilute sulphuric acid and 2 drops of
potassium dichromate solution (0.1%). Warm gently noting the color of the solution and smell
of the product.
Observation Inference
4. Iodoform test:
To 5 drops of the alcohol, add 5 drops of iodine solution (1% solution in 20% solution of potassium
iodide) and then add dilute sodium hydroxide solution drop wise until the colour of the iodine is
discharged.
Observation Inference
5. The Lucas test
In this test the OH group of alcohol is substituted by a group. Different classes react at different
rates. (Lucas reagent is 34.0 g of fused zinc chloride in 23.0 g of concentrated hydrochloric acid)
Place 5 drops of the alcohol in a test-tube and add 1 mL of the Lucas reagent. Shake the tube and
allow to stand for at least 5 minutes. Note how long the changes occur (if any).
Repeat the procedure with sample X.
Observation Inference
Identify sample X _________________________________________________________________________
Note: Clean all your apparatus, and return to their respective trays/trolleys. Wipe the bench tops with the provided
paper towel and dispose all waste generated as noted on the LAB Safety policy on notice boards. This is part of
experimental assessment.
