Crystallization - Organic Chem Lab

CRYSTALLIZATION


Objectives

• To show, by experimentation, the seven step process of crystallization by:

• Successfully determining the appropriate solvents for the solutes given

• Being able to dissolve the solute successfully in the chosen solvent

• Decolorizing the solution using Pelletized Norit

• Filtering Suspended Solids

• Crystallizing solute

• Collecting and Washing the Solute

• Drying the product

• To be able to use different compounds with precaution, especially when heating these compounds to a boil

• Understanding the method behind the 7 step process of crystallization and different experimental steps to obtain the same solution



Background Information: MSDS

Compounds Boiling Points (Celsius) MSDS Overview

Water 100 Flammability: 0 Health: 0, Reactivity: 0 (normally stable), Personal Protection: A – noncorrosive and non-irritant for skin. Nonirritant for lungs, eyes, indigestion, inhalation. When heated, it can become burn skin. When heated, must protect eyes and wear goggles.

Methanol 64.5 Flammability: 3, Health: 1, Reactivity: 0 (normally stable), Personal Protection: H, health hazard 2, and fire hazard 2. Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact (permeator).Flash Point: Closed cup 12 Celsius degrees and open cup 16 Celsius degrees. Soluble in hot or cold water.

Ethanol 78.5 Flammability: 3, Health: 2, Reactivity: 0 (normally stable), Personal Protection: H, health hazard 2, fire hazard 3. Hazardous in case of skin contact (irritant), of eye contact (irritant). Slightly hazardous in case of skin contact (permeator), of ingestion. Non-corrosive for skin, eyes and lungs. Flash point: closed up 18.5 Celsius degrees. Easily soluble in cold water, hot water, methanol, diethyl ether. Soluble in acetone.

Acetone 56.2 Flammability: 3, Health: 1, Reactivity: 0 (normally stable), Personal Protection: H, health hazard 2, fire hazard 3. Hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Slightly hazardous in case of skin contact (permeator). Flash point: closed up -20 Celsius degrees and open cup -9 Celsius degrees. Soluble in cold and hot water.

Acetic Acid 118.1 Flammability: 2, Health: 3, Reactivity: 0 (normally stable), Personal Protection: H, health hazard 3, fire hazard 2. Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (corrosive, permeator), of eye contact (corrosive). Liquid or spray mist may produce tissue damage particularly on mucous membranes of eyes, mouth and respiratory tract. Skin contact may produce burns. Inhalation of the spray mist may produce severe irritation of respiratory tract, characterized by coughing, choking, or shortness of breath. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening or blistering. Easily soluble in cold and hot water, diethyl ether, acetone. Miscible with Glycerol, alcohol, Benzene, Carbon Tetrachloride. Insoluble in Carbon Disulfide. Flash point: closed cup 39 Celsius degrees and open cup 43 Celsius degrees.

Phthalic Acid 295 Flammability: 1, Health: 3, Personal Protection: H, health hazard 3, reactivity 1, fire hazard 1. Considered not to be toxic to the environment so it can be washed down the drain. Very hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Hazardous in case of skin contact (corrosive, permeator), of eye contact (corrosive). The amount of tissue damage depends on length of contact. Eye contact can result in corneal damage or blindness. Skin contact can produce inflammation and blistering. Inhalation of dust will produce irritation to gastro-intestinal or respiratory tract, characterized by burning, sneezing and coughing. Severe overexposure can produce lung damage, choking, unconsciousness or death. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation is characterized by itching, scaling, reddening, or, occasionally, blistering. Flash point: closed up 151.67 Celsius degrees and open cup 165 Celsius degrees. Very slightly soluble in cold water, diethyl ether.

Sucrose N/A Flammability: 1, Health: 1, Personal Protection: X, health hazard 1, reactivity 0, fire hazard 1. Slightly hazardous in case of skin contact (irritant), of eye contact (irritant), of ingestion, of inhalation. Flash point: closed cup higher than 93.3 Celsius degrees. Easily soluble in cold water. Partially soluble in methanol. Insoluble in diethyl ether.

Acetanilide 304 Flammability: 1 (combustible at high temp), Health: 2, Reactivity: 0 (normally stable), Personal Protection: E. Hazardous in case of ingestion, inhalation, eye contact. Slightly hazardous in case of skin contact. Flash point is open cup, 173 Celsius degrees.

Benzoic Acid 249.2 Flammability: 1 (combustible at high temp), Health: 2, Reactivity: 0 (normally stable), Personal Protection: E. Hazardous in case of ingestion, inhalation, eye contact. Slightly hazardous in case of skin contact. Be sure to use under approved respirator. Flash point is closed cup, 121 Celsius degrees.

Salicylic Acid 211 (Dec) Flammability: 1 (combustible at high temp), Health: 2, Reactivity: 0 (normally stable), Personal Protection: E. Light and moisture sensitivity. Hazardous in case of ingestion, inhalation, eye contact. Slightly hazardous in case of skin contact. Be sure to use under approved respirator. Severe exposure can result in death. Flash point is closed cup, 157 Celsius degrees.

Anthracene 342 Flammability: 1, Health: 0, Reactivity: 0 (normally stable), Personal Protection: E, fire hazard 1. Very hazardous in case of skin contact (irritant, sensitizer), of eye contact (irritant), of inhalation. Hazardous in case of skin contact (permeator), of ingestion. Inflammation of the eye is characterized by redness, watering, and itching. Skin inflammation

is characterized by itching, scaling, reddening, or, occasionally, blistering. Flash point: closed up 121 Celsius Degrees. Insoluble in cold water.

Naphthalene 218 Flammability: 2 (combustible at high temp), Health: 2, Reactivity: 0 (normally stable), Personal Protection: E. Very hazardous in case of ingestion. Hazardous in case of eye contact (irritant), of inhalation. Slightly hazardous in case of skin contact (irritant, permeator). Severe over-exposure can result in death. Flash point: closed up 88 Celsius degrees and open cup 79 Celsius degrees. Partially soluble in methanol, n-octanol. Very slightly soluble in cold water, hot water



Materials

• Stainless steel spatula

• Reaction tube or a 10x75 mm test tube

• Calibrated dropped or Pastuer pipette

• Stirring rod (4 mm)

• Wash bottle

• Hot plate

• Erlenmeyer flasks

• 10-mL graduated cylinder

• Boiling stick – a stick of wood

• Cork ring

• Beakers

• Filter paper

• Hirsch funnel

• Hazardous waste container

• Nonhazardous waste container

• Decolorizing Charcoal (norit)

• Thermometer

• Aspirator tube



Procedure

1) Gather all needed materials for this experiment

2) Immediately wear safety goggles and apron and make sure to put all books away.

• For experiment 1:

1) To perform the solubility test for crystallization, first transfer about 10mg using a stainless steel spatula into a reaction or test tube of 10X75 mm.

2) Add .025 mL of solvent using a pipette

3) Stir with stirring rod (4mm) to break any lumps

4) Test different solvents such as methanol, ethanol, acetone, or acetic acid at room temperature to see if solute dissolves.

5) Keep trying different solvents until it does not dissolve

6) Once it does not dissolve, then heat suspension and see if solution occurs. Use either bath water or hot plate. Follow instructions on machinery as written. Use a beaker to place the tube for heating. If solute dissolves, it is soluble

7) Cool solution by holding flash under tap and if needed, induce crystallization by rubbing walls of tube with stirring rod

8) Reheat to dissolve solid,

9) Let solution stand undisturbed

10) Inspect character of crystals formed

• For experiment 2:

1) To crystallize pure phthalic acid, first crystallize 1 g of phthalic acid from minimum amount of water using data in lab

2) Add solid to the smallest Erlenmeyer flask

3) Use pipette to add water drop wise from a full 10 ML graduated cylinder

4) Use boiling wooden stick to prevent bumping

5) After addition of portion of water, gently heat on hot plate

6) As soon as boiling occurs, add water until all solid dissolves

7) Place flash on cork ring and allow it to cool undisturbed to room temperature

8) Observe crystallization

9) Cool flask in ice bath and decant by pouring off the mother liquid which is the liquid remaining with the crystals

10) Remove last traces of liquid with pipette

11) Scrape crystals onto filter paper using stainless steel spatula

12) Squeeze crystals between sheets of filter paper to remove moisture

13) Let crystals dry

14) Compare calculated volume of water with volume of water actually used to dissolve the acid

15) Calculate percent recovery of dry, recrystallized acid

16) To clean up, dilute filtrate with water and flush solution down the drain

• For experiment 3:

1) For decolorization of sucrose, dissolve 15g of dark sugar in 30mL of water in a 50mL Erlenmeyer flask by heating and stirring with stirring rod

2) Pour half of the solution into another 50mL flask

3) Heat one of the solutions nearly to boiling point and let it cool slightly

4) Add 250mg of decolorizing charcoal (norit pellets)

5) Bring solution back to boiling point for 2 minutes and filter the hot solution into flask through fluted filter paper held in a previously heated funnel

6) You may heat the funnel by turning it upside down and placing it on the hotplate for a couple seconds and then drying it off

7) Treat the other half of the sugar solution same way using only 50mg of decolorizing charcoal

8) Try heating solutions for only 15 seconds after addition of charcoal with lab partner and compare results

9) Clean up by decanting aqueous layer and placing charcoal in hazardous waste container. Flush sugar down drain

• For experiment 4

1) To purify an unknown, purify 100mg or 2 grams of an unknown as instructed

2) Test for solubility as shown above and also test for ability to crystallize in different solvents

3) Conserve unknown by using small quantities

4) If only drops of solvents used, solvent can be evaporated by heating the test tube on steam bath or sand bath

5) Submit as much pure product as possible, and identify the unknown

6) Clean up by placing decolorizing charcoal and filter paper in nonhazardous waste container. Put the organic solvents in organic solvents disposal container

7) Record all data and observations during all experimentations



Data & Calculations

Note: Please also see original laboratory report sheet initially provided, attached to post-lab.

Experiment 1: Solubility Test for Crystallizations: NOT DONE DUE TO INEFFICIENT TIME

Experiment 2: Crystallization of Pure Phthalic Acid:

o Mass of impure Phthalic Acid: .5174 grams

o Calculated Volume of Water Needed:

18 grams of Phthalic Acid / 100mL of H2O solvent = .5174 grams of Phthalic Acid / X

18X / 18 = 51.74 / 18 where X = 2.87 mL

o Actual Volume of Water Used: 5.5 mL

o Recovered pure Phthalic Acid: .3574 grams

(Recrystallized Phthalic Acid)

o Percent Recovery:

Collected Mass / Initial Mass = .3574 grams / .5174 grams = .6908 X 100 = 69.08%

o Melting point of recrystallized Phthalic Acid: Range of 77 – 81 degrees Celsius

Experiment 3: Decolorization of Brown Sugar (Sucrose, C12H22O11)

Mass of brown sugar weighed: 15.1111 grams

Volume of water used as solvent: 30 mL

Mass of decolorizing charcoal (Norit pellets) weighed: .2506 grams

 Part I: Results of 250mg (.25 grams) of charcoal: Qualitative data shows that brown sugar solution changed in appearance slightly after addition of 250mg of charcoal. Dark brown color changed to a slightly lighter dark brown complexion.

(Brown Sugar Solution prior to Addition of Norit pellets)



(Norit Pellets)

(Brown Sugar Solution after Addition of Norit pellets)

 Part II: Results of 50mg of charcoal: NOT DONE DUE TO INEFFICIENT TIME

 Part III: Results of short heating cycle: NOT DONE DUE TO INEFFICIENT TIME



Observations

In experiment 2, after calculating the amount of water required for recrystallization of pure Phthalic Acid, about 5.5 mL of water was used instead. This was done by accidently during experimentation and not realized until during the forming of the crystals. At that point, further filtration method of a vacuum was used to isolate the crystals from the excess water. Also note the small size of the formed crystals, compared to the results of other lab students, which were much bigger in size (as shown in the picture). The crystals were thoroughly dried when weighed afterwards since they were left in the lab for 2 full days. This allowed the percent recovery to be more accurate.

In experiment 3, it is to be noted that only about .25 grams of decolorizing charcoal was used. This experiment required the brown sugar to be split into two different solutions, with one having .25 grams of the Norit pellets in it, and the other .50 grams. With only .25 grams being used for the whole solution (much more volume), the solution only slightly changed colors, from dark brown to a lighter dark brown (as shown in the pictures). Upon those who did have the time to try the experiment with .50 grams of Norit pellets, it was witnessed that color change was much more intense and noticeable, causing the brown sugar to become a lighter caramel complexion.



Conclusion with Mention of Possible Errors

Two experiments were performed in this lab write up involving the 7 steps of crystallization. Experiment one involved using these steps to crystallize pure Phthalic Acid and the other experiment focused on decolorizing a brown sugar solution using Norit Pellets. In experiment one; Phthalic Acid was made into a solution with water as a solvent. The acid only dissolved into the solvent once it was brought to a boil. A definition of a good solvent explains how a solvent that will dissolve the solute when the solution is hot but not when the solution is cold. This is because if the crystals dissolve instantly at room temperature, then it cannot be used for recrystallization of the solute since too much of the solute will be part of the solution at a lower temperature. Since too much of the solvent was used, when the solution came to a boil and it was time to cool it down for the crystals to begin forming, there was too much solvent present. Using a vacuum to eliminate the excess water helped filter out the solute. Activated charcoal has a large surface area and can absorb the impurities in a solution that needs to be decolorized. When using Norit pellets to decolorizing the brown sugar, it is important to note the amount of the pellets and also the volume of the solution targeted. The lesser the volume of the solution or the greater the amount of the activated charcoal, the more significant the changes in appearance (color) will be. In the experiment performed, since the solution was not split into two different flasks and only .25 grams of charcoal was used, the colors did not differ much. If the situation was ideal, a light caramel complexion should have been observed. Some of the errors in this lab involved using excess water in experimentation 1, when making a solution for the Phthalic Acid. This error resulted in having to use a vacuum to filtrate the forming crystals, which resulted in dramatic loss of product. When transferring the product from the Erlenmeyer flask to the Hirsch funnel, it became apparent that some of the product was stuck to the inside walls of the flask and could not be removed. Also, when taking out the product on the filter from the Hirsch funnel, some of the wet crystals fell on the table and were unable to be recovered. With 69.08% recovery of Phthalic Acid, about 30.92% of the Phthalic Acid was lost in the methods stated above. Another reason could be that water is such a good solvent that it removed impurities in the original compound as well.