0.8 Organic reactions  (Page 2/3)

Experimental procedure

CAUTION WEAR EYE PROTECTION!

CAUTION - Concentrated sulfuric acid will burn and stain the skin as well as damage clothing. In case of skin or clothing contact, wash the area immediately with large amounts of water.

Synthesis of esters

• Place approximately 2 g (or 2 mL if the substance is a liquid) of the organic acid and 2 mL of the alcohol in a large test tube.
• Add 5 - 7 drops of concentrated (18 M) sulfuric acid, mix the solution well with a glass stirring rod and then place the test tube in a hot water bath (largest beaker in your drawer) (~ 80°C) for 5 - 10 minutes.
• Remove the test tube from the hot water bath and cautiously pour the mixture into about 15 mL of saturated sodium bicarbonate contained in a small beaker. The sodium bicarbonate will destroy any unreacted acid.
• Observe the aroma produced from each of the following esterification reactions. Write the structure of the esters produced, and the balanced equations for the esterification and the acid/sodium bicarbonate reactions:

Complete the following reactions using the procedure above and record your observations.

 (1) $C_7{H}_6{O}_3+{\text{CH}}_3\text{OH}\to$

 salicylic acid + methyl alcohol

 (2) ${\text{CH}}_3{\text{CH}}_2\text{CH}{}_2{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2{\text{CH}}_2\text{OH}+{\text{CH}}_3\text{COOH}\to$

1 - octanol + glacial acetic acid

 (3) ${\text{CH}}_3{\text{CH}}_2\text{CH}{}_2{\text{CH}}_2{\text{CH}}_2\text{OH}+{\text{CH}}_3\text{COOH}\to$

 amyl alcohol + glacial acetic acid

(4) $C_{2}H{}_5\text{OH}+{\text{CH}}_3\text{COOH}\to$

ethanol + acetic acid

Oxidation of an alcohol with acidified potassium dichromate(vi) solution

• Add 10 drops of dilute sulfuric acid (6M) and 5 drops of potassium dichromate(VI) solution (0.01M) to 5 drops of ethanol. The oxidising agent is added slowly to the alcohol so that the temperature is kept below that of the alcohol and above that of the carbonyl compound. (Carbonyl compounds are more volatile than the corresponding alcohols). Usually the alcohol is in excess of the oxidant and the aldehyde is distilled off to avoid further oxidation.
• Note the color and smell cautiously (Royal Wave).
• Warm the mixture and smell cautiously (Royal Wave).
• Repeat the experiment using first methanol and then propan-2-ol in place of ethanol.

Describe what happens and explain the color changes.

What conditions and techniques would favour the oxidation of ethanol to

a. ethanal rather than ethanoic acid.

b. ethanoic acid rather than ethanal?

Oxidation of an alcohol with acidified potassium permanganate (vii) solution

• Add 10 drops of dilute sulfuric acid and 5 drops of potassium permanganate (VII) solution (0.01M) to 5 drops of ethanol. Note the color and smell cautiously.
• Warm the mixture and smell cautiously (Royal Wave).
• Repeat the experiment using first methanol and then propan-2-ol in place of ethanol.
• Take the pH of your final mixture using Universal indicator paper

 Describe what happens and explain the color changes.

What is your final product?

Saponification of a vegetable oil

CAUTION - Sodium hydroxide is a very caustic material that can cause severe skin burns. Eye burns caused by sodium hydroxide are progressive: what at first appears to be a minor irritation can develop into a severe injury unless the chemical is completely flushed from the eye. If sodium hydroxide comes in contact with the eye, flush the eye with running water continuously for at least 20 minutes. Notify your TA immediately. If sodium hydroxide is spilled on some other parts of the body, flush the affected area with running water continuously for at least 2-3 minutes. Notify your TA immediately.