Study of the properties of monohydric alcohols

№6 Laboratory work.

Topic: Study of the properties of monohydric alcohols.

Objectives: 1. To get acquainted with the physical and chemical properties of monohydric alcohols, for example, ethyl alcohol.

Reagents and equipment: absolute ethyl alcohol, sodium metal, gas tube stopper, phenolphthalein, test tubes, copper wire, potassium dichromate, concentrated sulfuric acid, alcohol lamp.

Experiment №1: Determination of alcohol content and alcohol dehydration.

Necessary equipment: alcohol (rectified), copper sulfate CuS0₄*5H₂0 (powder).

Procedure: mix 1.5-2 g of copper sulfate on a porcelain plate with copper wire and heat until the blue color of the salt disappears and the release of water vapor stops. Cool the white powder and place in a dry test tube, add 2-3 ml of ethyl alcohol. With shaking, stirring and heating, the white powder in the vial quickly turns blue.

The resulting dehydrated alcohol is separated and used for the next work.

 Experiment №2: Formation and Hydrolysis of Alcohol.

 Necessary equipment: ethyl alcohol (dehydrated), sodium metal.

 Procedure: Put freshly cut, purified, dried metallic sodium from kerosene in dehydrated ethyl alcohol (dehydrated) like a pea. Dip the mixture into a test tube in a glass of cold water so that it does not heat up and the alcohol does not boil. When the gas begins to spread evenly, put a flame of fire in the mouth of the test tube. Evolved hydrogen: combines with air with a characteristic sound, ignites.

 The liquid gradually thickens, becomes covered with a layer of solid alcohol and slows down the reaction. Heat slowly to keep the reaction going. If hydrogen evolution stops, Na is completely insoluble. Undissolved potassium granules are removed with a flexible wire and placed in a jar with the remaining sodium. The resulting concentrated alcoholic solution crystallizes upon cooling. Add 5-6 ml of water to the test tube and check the phenolphthalein solution.

 Experiment №3: Oxidation of ethyl alcohol in a mixture of chromium.

 Necessary equipment: ethyl alcohol, potassium dichromate (5% solution).

 Procedure: Add 2 ml of potassium dichromate solution, 1 ml of dilute sulfuric acid and 0.5 ml of ethyl alcohol to the test tube and heat slowly, the solution will lose color and turn green. The reaction proceeds quickly and produces a characteristic acetaldehyde odor. Chromium is oxidized to 6 valencies.

 Experiment №4: Oxidation of ethyl alcohol with potassium permanganate.

 Required equipment: ethyl alcohol, potassium permanganate (crystalline).

 Procedure: 0.5 g in a test tube with a conductive tube. Add KMnO₄, 3 ml water and 0.5 ml ethyl alcohol. On the melting side, the reaction is fast. Therefore, cool the tube in a glass of water. The mixture is heated for 1-2 minutes to a boil, then 3 ml of dilute sulfuric acid is added, a boiling stone is added, the tube is connected and about 0.5 ml of liquid is injected into the receiving tube. Determines the smell of distillation and the influence of litmus on the reaction. The qualitative reaction is carried out with acetic acid (with FeCl₃ solution).

 Experiment №5: Extraction of Iodoform from Alcohol.

 Necessary equipment: methyl alcohol, ethyl alcohol, their close analogues, ethylene glycol.

 Procedure: mix 3-4 drops of alcohol and 2-3 ml of water in a test tube. The resulting solution is carefully heated, 0.5–1 ml of iodine solution is added, and alkali solution is added dropwise until the color of the solution disappears. Iodoform precipitates have a light yellow color and a characteristic Iodoform odor.

 Test questions:

1.        Write the reaction of sodium ethylate formation.

2.        Explain that adding water after hydrogen evolution stopped the removal of the white precipitate.

3.        Write the reaction equations for the production of acetaldehyde from ethylene.