Change Ethanol to Bromoethane

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid with the structural formula CH3CH2OH, often abbreviated as C2H5OH or C2H6O. A psychoactive drug and one of the oldest recreational drugs known, ethanol produces a state known as alcohol intoxication when consumed as a beverage. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a solvent, and as a fuel. In common usage, it is often referred to simply as alcohol or spirits.

Bromoethane, also known as ethyl bromide, is a chemical compound of the haloalkanes group. Its CAS NO is 74-96-4. It is abbreviated by chemists as EtBr. This volatile compound has an ether-like odour. In organic synthesis, Bromoethane is the synthetic equivalent of the ethyl carbocation (Et+) synthon. In reality, such a cation is not actually formed. For example, carboxylates salts are converted to ethyl esters, carbanions to ethylated derivatives, thiourea into ethylisothiouronium salts, and amines into ethylamines.

Here is an experiment about the conversion of ethanol to Bromoethane, This experiment could be done by advanced pupils, if sufficient fume cupboards were available. Alternatively it could be a teacher demonstration. It takes about 20 minutes.

Health, safety and technical notes

Wear goggles throughout. Work in a fume cupboard. Wear protective gloves when handling phosphorus tribromide.  
Ethanol (HIGHLY FLAMMABLE) or Industrial Denatured Alcohol, IDA, C2H5OH(l), (HIGHLY FLAMMABLE, HARMFUL) - see CLEAPSS Hazcard. 
Phosphorus(III) bromide (phosphorus tribromide), PBr3(l) (CORROSIVE). Similar to phosphorus(III) chloride - see CLEAPSS Hazcard. The vapour will hydrolyse in the moisture in air to give HBr (CORROSIVE) - see CLEAPSS Hazcard.

Procedure of this experiment

a. Put 20 drops of ethanol into a test-tube.
b. By adding one drop at a time, put 15 drops of phosphorus tribromide in the test-tube.
c. Leave the mixture to stand for 10 min.
d. Put 2 cm3 of deionised water in a measuring cylinder and, one drop at a time, add the water to the test-tube.
e. Observe the test-tube carefully. What do you notice?

The teaching notes

This is an alternative method to heating the alcohol under reflux with sodium bromide and concentrated sulfuric acid, generating HBr in situ. Yields by the HBr method are seldom impressive.

The phosphorus tribromide reacts vigorously with the ethanol and it is important that it is added only one drop at a time. The reaction is:
PBr3 + 3C2H5OH → 3C2H5Br + H3PO3
This is a nucleophilic substitution reaction.
The water removes excess PBr3 by the hydrolysis reaction:
PBr3 + 3H2O → 3HBr + H3PO3
A few globules of bromobutane should be seen at the bottom of the tube.

This is a brief introduction about the conversion of ethanol to Bromoethane, Want to learn more information about Bromoethane, you can access the guidechem.com. Guidechem.com is just a place for you to look for some chemicals.