Experiment 3. Qualitative reactions to vitamin С (ascorbic acid).

LABORATORY WORK

"QUALITATIVE REACTIONS TO VITAMINS AND HORMONES"

Experiment 1. Reaction of vitamin В1 (thiamine) oxidation into thiochrome.

Pour 0,5 ml of thiamine solution in the test tube, add 6 drops of 5% К₃[Fe(CN)₆] solution and 1 ml of 30% sodium hydroxide solution and mix. Then add 1 ml of isobutyl alcohol and shake intensively during 1-2 minutes. Put test tube in the UV-box. What do you see in UV-rays?

Than heat the mixture in the test tube in a water bath, stirring.

The sings of the reaction are caused by thiochrome formation:

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Thiamine chloride

Thiochrome

Experiment 2. Reaction of vitamin В6 (pyridoxine) with iron chloride (III).

Pyridoxine is a general name for a group of chemical compounds that possess the activity of vitamin В₆:

pyridoxol pyridoxal pyridoxamine

The reaction with FeCl₃ is caused by the presence of phenol hydroxyl group in the vitamin В₆ molecule. A complex compound of iron phenolate type is formed.

Pour 0.5 ml of 5% vitamin В₆ water solution into a test tube; add 2 drops of 5% iron chloride solution.

Experiment 3. Qualitative reactions to vitamin С (ascorbic acid).

This reaction is based on the ascorbic acid property to be easily oxidized or reduced.

Pour 5 ml of 0,02% vitamin C solution in the test tube, add some drops of 5% potassium hydroxide solution and 10% К₃[Fe(CN)₆] solution and mix, then add 3 drops of 10% hydrochloric acid solution and 2 drops of 10%iron chloride (III) solution.

L- ascorbic acid L- dehydroascorbic acid

3K₄[Fe(CN)₆] + 4FeCl₃ → Fe₄[Fe(CN)₆]₃ ↓ + 12KCl

Berlin blue

(ferric ferrocyanide)

Дата добавления: 2015-11-14