Demonstration of diethyl ether

Chemicals needed

ice or snow
ethanol  F    R 11    S (2)-7-16

or denatured alcohol
sulphuric acid 96 %  C    R 35   S (1/2)-26-30-45

Hazardous substances

diethyl ether  F+      R 12-19-22-66-67     S (2)-9-16-29-33

Equipment necessary

2 test tubes (1 normal, 1 small)
rubber stopper with hole and discharge tube
stand with double sleeve and clamp
beaker (or the like)
burner (preferably alcohol-)

Test procedure

• Safety goggles! Ventilation! Flames, except when needed, are to be extinquished.
• In the (normal) test tube one adds initially approx. 3 ml ethanol, then one carefully adds approx. 1.5 ml concentrated sulphuric acid.
• The mixture, which possibly becomes somewhat brown, should be carefully swayed back and forth. If this does not happen, then it will at first boil with eructation.
• One clamps the test tube steeply or vertically in the stand, one puts the stopper with the discharge tube on, such that the discharge tube leads into a test tube, which itself is placed into a beaker filled with snow or ice water. In order to avoid recoil the discharge tube should discharge a goodly distance from the bottom. Between the flame and the beaker one should maintain a certain distance in order to avoid the inflammation of the produced ether.
• The mixture is heated with the burner and is keep boiling slightly, it will thereby become deep brown or even black. Do not overheat and only until a good half of the mixture has been distilled off. A clear distillate collects in the beaker. After termination of distillation the burner is to be immediately extinguished and before opening of the apparatus one should wait minimally about a minute.
• The product is, as one can easily verify, barely water soluble and lighter than water. It has a characteristic smell, which can, however, due to by-products seem somewhat burnt. The later can be reduced if one ends the distillation process prematurely.

Disposal

• One carefully adds (temperature rise) to the reaction mixture one to two times the volume on water and disposes of it as a halogen-free organic waste.
• Ether is also a halogen-free organic waste. Inasmuch as it is rather irritating due to its volatility, it is also practical to burn the small amount on a watch glass or in a crucible. Hereby one should be careful due to evaporation (formation of an explosive mix with air)!
• If water does not suffice, one can remove the tarry remnants in the reaction vessel with acetone. This can then also be disposed of as halogen-free organic waste.

Elucidation

The dehydrating and acidic effects of the concentrated sulphuric acid promote the seperation of water from alcohol. At medium temperatures (130°C) one molecule of ether thereby results, primarily out of two molecules of alcohol, at higher temperatures (170°C) one molecule of ethylene results out of one molecule of alcohol.

2 CH3CH2OH --> CH3CH2OCH2CH3 + H2O

Photos:

Experimental apparatus before distillation.

Experimental apparatus after the termination of distillation.

Literature

A traditional experiment. Mentioned in many older textbooks.

z.B [2]