Experiment 3 2019 PDF

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Same lab experiment as 2019/2020...

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Experiment #3 Extraction of Anthocyanidins from Red Cabbage for use as pH indicator Brent Hertel February 13th, 2019 Organic Chemistry 3123-102 Laboratory TA: Joseph Medina

Abstract: The purpose of this experiment is to use red cabbage as an indicator to the solution that can determine their pH indicator. A colorimetric pH indicator is a chemical compound added in small amounts to a solution so the pH of the solution can be determined visually. These indicators are frequently employed in titrations in analytical chemistry and biology. Anthocyanins can be employed as colorimetric compounds because they change color at different pH values. The anthocyanins motif exhibits subtle structural changes dependent on fluctuation in pH. In an acidic environment with a pH less than 7, the compound takes on a different form. At this point it is expected to be around a reddish pink color. While in a neutral environment, with a pH of 7, it is a purple color and appears as a different structure. On the other hand, in a basic environment with a pH above 7 it is a blue-greenish color. In this laboratory, anthocyanidin was extracted from cabbage and was put into different test tubes with different solutions to determine the visual effect of different pH levels. The end results of the lab resulted in different colors of mixtures indicating the different pH levels in each solution.

MSDS:

1.0 M Hydrochloric acid: Causes severe skin burns and eye damage, Do not breathe mist, vapors, spray, Wash exposed skin thoroughly after handling, Wear protective gloves, eye protection, protective clothing, face protection Health: 3 Fire: 0 Reactivity: 1

1.0 M Acetic Acid: Body tissue irritant and moderately toxic by ingestion. Target organs: Respiratory system, eyes, skin, teeth. Health: 3 Fire: 2 Reactivity: 1

Ascorbic acid C6H8O6: Body tissue irritant and moderately toxic by ingestion. Target organs: Respiratory system, eyes, skin, teeth. Health: 0 Fire: 0 Reactivity: 0

Sodium Bicarbonate, NaHCO3: Causes eye irritation. Skin: Causes skin irritation. May be harmful if absorbed through the skin. Ingestion: May be harmful if swallowed. Causes gastrointestinal tract irritation. Health: 2 Fire: 0

Reactivity: 1

1.0 M Ammonia, NH3: Flammable gas [Warning Flammable gases] Contains gas under pressure; may explode if heated [Warning Gases under pressure] Causes severe skin burns and eye damage [Danger Skin corrosion/irritation] Health: 3 Fire: 0 Reactivity: 0

Procedure: Obtain 10-15 grams of red cabbage and wash. Tear the cabbage into small pieces and place into a large beaker with 150mL of deionized water. Over a hot plate boil until the water is a dark purple color. After about a 5-10min of rapid boiling, remove the beaker from the hot plate and let cool. Extract excess cabbage using a filter. In this experiment it is important to keep the liquid. Discard the solid into the trash. Be sure to add a specific amount of liquid in each designated test tube for most precise results. Add 3ml of red cabbage to each of the test tubes. Make sure to stir with a glass rod to ensure complete dissolution and consistency. The reactions occur very quickly. Take note of each color change. Part two is the preparation of a buffer solution. Add Acetic acid and sodium acetate into a test tube and stir. Add 3 ml of red cabbage extract into the mixture and take note of the color change. Data

Test tube #1 Hydrochloric acid #2 Acetic Acid #3 Ascorbic acid #4 Nothing (control group) #5 Sodium bicarbonate #6 Ammonia #7 Distilled Water #8 Acetic acid + Sodium acetate (buffer)

Color Pink Pink Red Purple Light green Dark green Light purple Light Pink

Mass of Red Cabbage: 15.554 Mass of solid Ascorbic acid: 0.1001g Mass of sodium bicarbonate: 0.103g Mass of solid sodium acetate: 0.410g Calculations: NONE Notes/Observation If water is not a dark color after boiling, the beaker must be cleaned and will not be able to continue procedure. Yellow to red colors indicate a more acidic solution (pH between 0-7) Purple colors indicate a solution is neutral (pH of 7) Blue to green colors indicate a solution is more basic (pH between 7-14) Conclusion: In conclusion, the test tubes that were red and pink colors were acids with a pH of between 0-6. These solutions contained hydrochloric acid, acetate acid, and ascorbic acid. Test tube #4 was a

neutral with a pH of 7. For sodium bicarbonate and ammonia, these solutions were a basic with a pH of 8-14 due to the green color the solutions gave off.

References: Organic Chemistry 1 Laboratory manual by Dr. Jason Abrams...