SCI 122 GEN CHEM II LAB Manual PDF

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SCI 122 General Chemistry II Laboratory Manual First Edition

Dong Ma, Ph.D. Kimberly Stieglitz, Ph.D. Science Department

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Acknowledgement We are grateful to Professor Kimberly Stieglitz of Roxbury Community College who initiated this work and provided the crucial advices through the course of writing. We thank STEM division of Roxbury Community College for the support. We thank the laboratory staff of STEM division for providing laboratory supplies and equipment for the pilot experiments. We thank Adjunct Professor Farida Akhter of Roxbury Community College for using the pilot experimental procedures and providing many suggestions on the experimental procedures.

TABLE OF CONTENTS Chemistry Laboratory Safety Guidelines...................................................................................4 Chemistry Laboratory Safety Agreement ..................................................................................6 Laboratory Schedule ..................................................................................................................7 LAB 1: Purification of an Organic Compound by Recrystallization.........................................8 LAB 2: Organic Compounds: Hydrocarbons ..........................................................................17 LAB 3: Alcohols and Phenols..................................................................................................27 LAB 4: Aldehydes and Ketones ..............................................................................................38 LAB 5: Carboxylic Acids and Esters .......................................................................................48 LAB 6: Amines and Amides ....................................................................................................56 LAB 7: Aspirin and Other Analgesics .....................................................................................69 LAB 8: Synthesis of Acetaminophen ......................................................................................81 LAB 9: Lipids ..........................................................................................................................89 LAB 10: Amino Acids .............................................................................................................99 LAB 11: Proteins and Enzymes .............................................................................................109

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Safety Guidelines The Chemical Laboratory is a place which has more potential danger than most other locations on campus. It is important that everyone be aware of their environment and to work in a safe and responsible manner. Working safely in a laboratory environment depends on three major factors: 1) Using your common sense. If you think something appears to be dangerous or unusual ask the instructor to check your workplace. In all cases follow your instincts and keep yourself from harm. 2) Following the directions of the instructor and staff. If the instructor or RCC laboratory staff give you a direction or order you should follow their instructions immediately in what you would consider a safe and prudent manner. If you are told to evacuate the laboratory do so quickly and in an orderly manner by leaving through the primary exit (the door you enter the lab from). 3) Being careful and alert to what is around you. You are surrounded by other students normally performing the same experiment as you are but in a different location. Be aware of what other people are doing as well as observing your own experiment. Does something seem very different with your experiment compared to others? Do you see something that might not be safe? If there is a problem only 3 feet from your location it is likely to affect you -- so, talk with your classmates or the instructor if something seems out of place (following #1 above).

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Roxbury Community College Chemistry Laboratory Safety Guidelines In addition, there are other rules and regulations that will ensure a safe and productive semester of laboratory work. Those rules are as follows: • In the case of an extreme emergency have the instructor or laboratory staff go to security or pick up the phone in the laboratory. Security should answer the phone. Do not dial 911. • There is no eating or drinking in the laboratory. • Goggles are provided (which ensures they are chemically resistant) must be worn at all times after any pre-lab lecture provided by the instructor. • Only water goes down the drain! There will be a waste container for all materials used in your experiment. If the waste container is not obvious ask the instructor. • Dispose of all glass (broken, disposable or damaged) in the broken glass disposal box in the front the laboratory (not in the trash). • If unsure about a procedure, ask the instructor before continuing an experiment. Even the order of mixing some materials may be important. Follow the instructions from your instructor or the laboratory staff in the case of an emergency. • Be aware of the primary and secondary exits that should be used in an emergency (fire or chemical spill). Always know where these exits are relative to your workspace. • Know where the safety shower and eye wash stations are relative to your workspace. The shower is near the door in the front of the laboratory; the eye wash station is just to the right or left of the sinks in the center of the lab. In the event of a major chemical spill which gets on your clothing you will have to remove that clothing and use the safety shower. Small spills which do not contact clothing can be washed off at the sink areas in the laboratory. • Any materials which are expected to generate a harmful or noxious gas should be used in the fume hoods in the back of the laboratory. If your experiment unexpectedly starts generating a gas which you feel is harmful transport the experiment to the hood if you can do so safely and notify the instructor. • If you have a fire at your workspace remove all flammable materials, shut off all natural gas supplies and smother the flames if possible using large beaker or other object. If the fire is substantial move away and call out to the instructor. There is a fire extinguisher near the prep room door but it should be used only by qualified personnel.

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Roxbury Community College Science Department

Chemistry Laboratory Safety Agreement As a student enrolled in a chemistry laboratory course at Roxbury Community College: • I agree to observe all safety regulations as listed in the lab syllabus, lab manual and supplemental handouts. • I have witnessed and understood the safety instructions and procedures presented today by the instructor. • I agree to follow all verbal instructions of the instructor and staff and agree to wear goggles provided at all times during the laboratory session unless specifically told by the instructor that they are not necessary. • I understand that if I violate any safety regulation, I may be asked to leave the lab and will accept a zero score for that lab exercise. • I acknowledge that continued disregard for safety on my part will result in my being dropped from the course. General ChemistryII ____________

Fall

Course Number:

Spring

Summer

year

Section Number:

Instructor:

Name of Student (printed): Today’s Date:

Signature:

____________________________ Please pass in to the Laboratory Manager or Instructor

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SCI 122 GENERAL CHEMISTRY II LABORATORY PASTE A COPY OF YOUR LAB SCHEDULE FROM YOUR SYLLABUS HERE

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SCI122 General ChemistryII Laboratory 1: Purification of an Organic Compound by Recrystallization LABORATORY GOALS • • • •

Learn the principle of recrystallization. Determine a suitable solvent by experiments. Study the quantitative effects of the solvent on the isolation of a compound. Isolate and purify an organic compound by recrystallization.

LAB INFORMATION Time: 2-3h Related topics: Organic compounds, structural formula, physical property of organic compounds, solubility of organic compounds, recrystallization, DISPOSE OF ALL CHEMICALS AS DIRECTED BY YOUR LAB INSTRUCTOR. CHEMICAL CONCEPTS A. Recrystallization Impurities cause contaminations in synthetic organic molecules or natural compounds isolate from raw resources. Recrystallization is a technique of purification used to remove impurities from natural and synthetic organic compounds that are solids at room temperature. This process is based on the condition that the solubility of a compound in a solvent increase as temperature of the solution increases. Likewise, the solubility of the compound decreases as the solution cools. This is the reason why crystals are formed when solution is cooled to a certain temperature. Recrystallization allows the formation of highly pure compounds. As a heated solution of the target compound cools, a small, pure seed crystal of the compound forms in the solution. Then, more molecules attach to this crystal layer by layer, forming a growing crystal lattice, as shown in Figure 1.1. The molecules in the crystal have a greater affinity for other molecules of the same kind than they do for any impurities present in the solution. Practically, the process of crystallization removes one type of molecule from the solution.

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Figure 1.1(a) Identical molecules attach to one another, forming a crystal lattice

Figure 1.1(b) impurities have different shapes or sizes and do not pack together.

B. Identify a suitable solvent A solvent is the most abundant substance in a solution that dissolves a solute – a unique and relatively small amount of solid, liquid and gas substance. Selecting an appropriate recrystallizing solvent to use is the most important step in recrystallization. The key to choose the solvent for a recrystallization is to consider the extent to which the solute and impurities are soluble in the solvent at both high and low temperatures. The graph in Figure 1.2 shows how temperature affects the solubility of the solute and the impurities. Ideally, the solute compound to be recrystallized should be very soluble in the chosen solvent at elevated temperatures, but almost insoluble in the cold solvent, as shown by line A. Impurities should be soluble in the chosen solvent at all temperatures so that impurities stay in solution as shown by line B. Alternatively, impurities should be insoluble at all temperatures so they can be filtered out of the hot solution, as shown by line C.

10 9

Solubility (g/ml)

B A

2 1 0

C Temperature oC

Figure 1.2. Ideal solubility patterns of a solute, line A, and accompanying impurities, lines B and C, at varying temperatures

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Choosing an appropriate recrystallizing solvent requires experimental trials and experience. First, the number of the solvents should be narrowed down to a few based on the structure of the compound. Then, the solubility of the compound in each of these solvent is tested on a small scale. Typically, a small amount of the compound is mixed with a few milliliters of each solvent. The compound’s solubility is observed at room temperature and close to the solvent’s boiling point. If the compound is soluble in a solvent at room temperature, the solvent is not suitable. If the compound is insoluble at room temperature and soluble close to the solvent’s boiling point, the solvent is a possible choice. Note that “insoluble” is a relative term. For example, benzoic acid in water has a solubility of 6.80 grams per 100 ml at 100°C. However, benzoic acid has a solubility of only 0.34 gram per 100 ml at room temperature 25°C. Therefore, benzoic acid is usually listed insoluble at room temperature in water. When selecting solvents, a general rule, “like dissolves like”, is often applied. Organic molecules contain functional groups that can form hydrogen bond, such as –OH, ‐NH2, and COOH are polar and generally more soluble in polar solvents. Many organic molecules are nonpolar and are mostly soluble in nonpolar solvents. A list of commonly used recrystallization solvents are shown in Table 1.

Solvent water methanol ethanol (95%) acetone ethyl acetate

bp (oC) 100 65 78 56 77

Solvent ethyl ether dichloromethane toluene petroleum ether

bp (oC) 35 40 111 35-60

Table 1.1 Commonly used recrystallization solvents, in order of decreasing polarity* The boiling point of a recrystallization solvent must be lower than the melting point of the compound to be recrystallized. Otherwise the compound will oil out which occurs when a compound is insoluble in a solution at a temperature above the compound’s melting point. In the case of oiling out, the compound becomes oil or oily suspension instead of forming crystals. Another criteria for selecting a recrystallizing solvent is that the solvent must be able to produce an abundant crystals as the solution cools down to room temperature or 0°C. Here is a summary of the four important criteria when selecting a recrystallization solvent: 1. Compound being purified must be insoluble in solvent at room temperature. 2. Compound must be soluble at high temperature or in boiling solvent. 3. The boiling point of the solvent must be lower than the compound’s melting point. 4. An abundant quantity of crystals must be produced from the cool solvent.

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EXPERIMENTAL PROCEDURE: 1. Select a suitable solvent 1. Measure solid samples on weight boats or weight paper with electric scales. Measure liquid samples with 20ml graduated cylinders. 2. Place 0.22 – 0.18 g acetylsalicylic acid in 4 test tubes which are labeled as 1, 2, 3 and 4. Record all digits from the electric scale. 3. Add 4.0ml of ethanol, 2-propanol, distilled water and toluene each to the test tube 1, 2, 3 and 4 respectively. Make sure the cylinder is clean and dry before it is used on the next liquid. Stir the test tubes with glass rods. Use hot water bath to heat the test tubes when needed. 4. Based on the results, identify at least one suitable solvent for acetylsalicylic acid. Use the Table 1.1 in the report sheet to record the observation. 5. Test the solubility of sugar in the above solvents without heating, following the same method for testing acetylsalicylic acid (step 2 to step 4). Use the Table 1.2 in the report sheet to record the observation. 6. Based on the observations, identify the solvent suitable for the separation and purification of acetylsalicylic acid you will do in Part 3. Remember, a suitable solvent will be one in which the sugar will dissolve at a low temperature. 2. The effect of the solvent quantity After a proper solvent for a recrystallization is determined, the quantity of the solvent must be carefully chosen. Enough solvent must be used so that the sample dissolves when heated, but if too much solvent is used the solution does not become saturated on cooling and nothing is recovered. To demonstrate this principle, you will observe the effect of water quantity on the recrystallization of acetylsalicylic acid. 1. Place 0.2g acetylsalicylic acid into three test tubes labeled with the numbers 1, 2, and 3. 2. Add 4.0 mL of distilled water to test tube 1, 8.0 mL of distilled water to test tube 2, and 12.0 mL of distilled water to test tube 3. 3. Heat the test tubes in a hot water bath to dissolve all acetylsalicylic acid samples. Stir with glass rods occasionally during the heating. 4. Remove all test tubes from the bath and allow them to cool for 10 minutes. Solid will precipitate and settle on the bottoms. Agitate the solvent with glass rods during the cooling. In Table 1.3, record the amount of solid observed, using relative words like none, some, and a lot to describe the quantities. 3. Recrystallization of Aspirin 1. Mass a sample of impure aspirin in the range of 0.5 to 0.6 g and place it into a clean test tube. Use Table 1.4 record the data. 2. Add 5.0ml the suitable solvent determined in activity 1 into the test tube. Place it in the boiling water bath (150ml beaker) for at least 5 minutes. Stir occasionally during the heating.

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3. After heating, remove the test tube from the bath and quickly decant most of the clear liquid into another clean and dry test tube. The undissolved solid will remain in the first test tube. Discard the solid. Do not remove the hot water bath. Instead, keep it hot on a hot plate. 4. Allow the second test tube to cool for 5 minutes. Stir the test tube several times while it is cooling. Acetylsalicylic acid should crystallize after cooling. Centrifuge the test tube for one minute (remember to keep the centrifuge balanced with another tube.) and decant the liquid from the test tube. Discard the decanted liquid. Your lab instructor will demonstrate the decanting. 5. Weight an empty watch glass and record it in Table 1.4.

Figure 1.3 Flow chart of the isolation and purification of acetylsalicylic acid* 6. Transfer the crystals obtained in step 4 onto the watch glass by using a spatula. Then, place it on the top of the hot water bath and heat to boil the water gently. Keep the watch glass there for 10mins to dry the crystals completely. 7. After drying, remove the watch glass from the boiling bath and let it cool to room temperature. Then weight the watch glass again and measure the melting point of the crystal. Record the data in Table 1.4.

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DATA SHEET * Table 1.1 Solubility of acetylsalicylic acid test tube #

solvent

1

ethanol

2 3

2-propanol water

4

toluene

cool solvent

heated solvent

suitable solvent?

Table 1.2 Solubility of sugar test tube #

solvent

1

ethanol

2

2-propanol

3

water

4

toluene

cool solvent

suitable solvent?

Table 1.3 Effect of solvent quantity volume of water

solid precipitate

2.0 ml 4.0ml 6.0ml Table 1.4 Recrystallization of aspirin mass of impure aspirin sample mass of empty watch glass mass of watch glass with purified aspirin observed melting-point range of purified aspirin * Independently reproduced from “Safety-Scale Laboratory Experiments for Chemistry for Today” by Spencer L. Seager, 8th Edition, Cengage.

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SCI122 LAB1 ISOLATION AND PURIFICATION OF AN ORGANIC COMPOUND Pre-lab study questions 1. Specify any safety precautions as one works in the experiment?

2. How would you measure the quality of the solid samples used in the experiment?

3. How would you measure the volume of solvent used in the experiment?

4. A solvent is the abundant part of a solution while a solute is usually limited and distinctive. List the solute(s) and the solvents used in Part 1 of the procedure.

5. In the recrystallization step, what is the technique applied to separate the solid from the solution?

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SCI122 LAB1 ISOLATION AND PURIFICATION OF AN ORGANIC COMPOUND Post-lab study questions 1. A student is following the directions correctly in Part 1 of the experiment and measures out 0.1 grams of acetylsalicylic acid and places in four separate test tubes with 2 mL of water, 2propanol, toluene, and ethanol. The student immediately notices that the acetylsalicylic acid goes into solution in ethanol at room temperature and decides ethanol is therefore the suitable solvent. Is the student correct? Why or why not? What is the ultimate goal of the experiment?

2. Go on the internet and find the structure of acetylsalicylic acid. Draw the structure here. Looking at the polar and non-polar ...