CH342Fall 2011

Lab package

Sample Theoretical and Percent Yield calculations:

CH3

CH3

CH2CH3

OH

CH3

CH3

CH2CH3

Cl

2-Methyl-2-butanol

+ Conc. HCl

2-Chloro-2-methylbutane

+ H2O

10.0 mLDensity = 0.805 g/mL 10.0 mL

12.1 molar 8.0 grams isolated

1 Write a balanced chemical equation for the reaction. Without this, the calculation is impossible. Most of the time, this is in the lab book or the lab handout. In the sample equation, one 2-methyi-2-butanol + one HCI gives one 2-chloro-2-methylbutane.2. Find the reactants. Solvents and catalysts do not influence the yield.3. Obtain or calculate the molecular weights of each reactant. 2-methyl-2-butanol has 5 carbons, 1 oxygen, and 12 hydrogens. Its molecular weight would be (5 x 12.01) + (1 x 16.00) + (12 x 1.008) = 60.05 + 16.00+12.10 = 88.15. 2-chloro-2-methyibutane is 60.05+16.00+35.45 = 106.59. HCl is 36.46, but we won't actually need this.4. Calculate the number of moles of each reactant. If we have grams, we just divide the grams used by the molecular weight (which has units of grams/mole). For 2-methyl-2-butanol, this is a little more difficult, since we are given mLs of 2-methyl-2-butanol. We need to use the density (which is in grams/mL) to get the grams of 2-methyl-2-butanol. From the Aldrich Catalog, the density of 2-methyl-2-butanol is 0.805. Therefore, 10.0 mL 2-methyl-2-butanol x 0.805 g 2-methyl-2-butanol/niL = 8.05 g 2-methyl-2-butanol. 8.05 g 2-methyl-2-butanol I 88.15 g 2-methyl-2-butanol I mole = .0913 moles 2-methyl-2-butanol. For conc. HCI, we are given molarity, which is in moles/L, so all we have to do is multiply 12.1 moles/L x .0100 L = .121 moles HCl.5. Find the limiting reagent. In our equation, one HCl + one 2-methyl-2-butanol give one 2-chloro-2-methylbutane. Therefore, whichever reagent has the fewest number of moles will control how much product is formed. We have 0.121 moles of HCl and 0.0913 moles of 2-methyl-2-butanol. Since we have less 2-methyl-2-butanol than HCI, 2-methyl-2-butanol is the limiting reagent, and we can form only 0.0913 moles of 2-chloro-2-methylbutane.6. Calculate the theoretical yield of product. The molecular weight of 2-chloro-2-methylbutane is 106.59. So, 0.0913 moles of 2-chloro-2-methylbutane x 106.59 g 2-chloro-2-methylbutanelmole =9.73 grams 2-chloro-2-methylbutane. This is our theoretical yield.7. Percent yield is what proportion of the theoretical yield we actually make. If we had produced 8.00 grams of 2-chloro-2-methylbutane when we actually did the reaction, then the percent yield is 100% X 8.00g/9.73g = 82.2%.

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CH342Fall 2011

Lab package

Report format for Learning Basic Operations: The Effect of pH on a Food Preservative

1. Title Page (Attach a separate Title page to your report)

A short descriptive title of the lab exercise.Date the experiment was performed.Course and section numbers.Name(s)

2. Body of the report

a. Amount of sodium benzoate used (gm) ___________________

b. Amount of sodium benzoate used (moles)____________________

c. Amount of 3M HCl used (ml) ____________________

d. Amount of 3M HCl used (moles) ____________________

e. Limiting reagent ____________________

f. Theoretical yield of benzoic acid (gm) ____________________

g. Actual yield of benzoic acid (gm) ____________________

h. Percent yield (Show calculation) ____________________

Show calculations for Theoretical yield and percent yields here. Indicate the Limiting Reagent in this reaction.

3. ExercisesDo Exercises 1 and 4 on page 47. If more space needed, use separate papers and attach them to this report.

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Report Format for

Separating the Components of Panacetin. Recrystallization and Melting Point Measurement: Identifying the Components of Panacetin

1. Title Page (Attach a separate Title page to your report)

A short descriptive title of the lab exercise.Dates the experiment was performed.Course and section numbers.Name(s)

2. Body of the report (start a new page)

Panacetin sample number _______________

Statement of the problem

Weight of initial panacetin sample _______________________

Weight of sucrose collected _______________________

Weight of aspirin collected _______________________

Melting point range of aspirin _______________________

Weight of unknown compound isolated in Expt. 2 _____________

Weight of recrystallized unknown compound in Expt. 3._________

Melting point range of recrystallized unknown compound _______

Mixture melting point ranges of the unknown compound with acetanilide ________

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Mixture melting point ranges of the unknown compound with phenacetin ________Percent recoveries of sucrose, aspirin and your unknown (divide the weight of each solid by answer in c., 100%). Show your calculations.

A final conclusion, supported by evidence, about identity of the unknown compound.

3. Exercises

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Do Exercises 1 and 5 on page 54, and Exercise 1 on page 60. Use separate papers to write answer the exercises and attach them to this report.INTRODUCTION TO THIN LAYER CHROMATOGRAPHY (TLC)

In this experiment, you will be identifying an unknown compound by TLC. Your unknown may have impurities added to it, including benzoic acid. Since the unknowns and benzoic acid all show up under UV light, we can easily detect them with TLC.

Procedure:

Obtain a TLC plate, and draw a light pencil line across the width of the plate, about 1 cm from the edge. Place 5 light “tic marks” on the line, approximately equally spaced.

In separate test-tubes, dissolve tiny amounts of your unknown in about 1 mL of acetone. Using one of the spotting capillary tube, spot a tiny drop of the acetone solution of your unknown on the first from the left “tic-mark” - you may want to practice spotting on a paper towel or tissue, to make small spots. Allow it to dry, and then check the plate under a short-wave UV light, to see if you have a visible spot. If not, spot your solution again on the same “tic-mark”. Do not spot any more times than needed - too much material may give results that are hard to interpret! After you have your samples spotted, take your plate to the standards in the hood, and spot benzoic acid on the second from the left “tic-mark”, three possible unknowns on the third, fourth and fifth “tic-mark”s. Keep track of which possible unknown spotted where. Do not get the spotting capillaries for the standards contaminated! Check the spots under the UV light, to see if they are all visible.

To prepare a developing chamber, obtain a piece of 11 cm filter paper, and fold it about 1 inch from the edge, to obtain a flat edge. Place the filter paper, flat edge down, in your 250 mL beaker. Obtain 15 mL of the TLC solvent, and pour it into the beaker, swirling the beaker to wet the filter paper with the solvent.Carefully place the TLC plate in the developing chamber, spotted side down, trying not to splash the solvent on the plate. The level of solvent must be below the pencil line. Cover the beaker with a watch glass. The solvent will rise up through the stationary phase on the plate. When the solvent has risen to 1-2 cm from the top of the plate, remove the plate, and draw a light pencil line across the plate, at the level to which the solvent rose. Allow the solvent to evaporate (waving the plate in the air will speed this up), and then look at the plate under the UV light. Circle all of the spots.

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CH342Fall 2011

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TLC Plate TLC Developing Chamber

Pencil line 1 cm from the end

“Tic marks”

Level of solvent below line of spots

Folded piece of11 cm Filter paper

TLC plate

400 mL Beaker

Watch Glass

A developed plate may look like this:

You will identify the components of your unknown tablet by comparing the amounts the components traveled up the plate with the amounts the standards traveled. These amounts are reported as Rf (retention factor) values.

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X

Y

CH342Fall 2011

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X Distance the spot traveledRf = --- = ------------------------------------ Y Distance the solvent traveledMeasure the distance a spot moves from the center of the spot. Separate R f values are calculated for each of the spots. Since the spots for the materials in the samples and in the standards are different sizes and shapes, they may have slightly different Rf values.

Cleaning Up

When you are finished with the experiment, pour the TLC solvent in the “Recovered TLC Solvent” container. The filter paper may be thrown away in the trash can. Used spotting capillaries should be placed in the “Clean Broken Glass” container. Your acetone solutions you used to spot with may be flushed down the sink with lots of water.

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CH342Fall 2011

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Report format for Identification of the Unknown Compound by Thin Layer Chromatography 1. Title Page (Attach a separate Title page to your report)

a. A short descriptive title of the lab exercise.b. Dates the experiment was performed.c. Course and section numbers.d. Name(s)

2. Body of the report (start a new page)

a. Unknown compound number _____________

b. Calculate Rf values (Show your work below) of each of the spots on your TLC plate (Attach TLC plate to this report).

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3. Questions

(a) What is the identity of your unknown solid? Explicitly explain your choice using the data you acquired.

(b) If your unknown compound and more than one of the possible unknowns produce similar Rf values when a 1:1 mixture of ethyl acetate and hexane is used to develop your TLC plate, how could you modify the TLC experiment so you can determine which one was your unknown? Explain your reasoning.

(c) Is it possible to have Rf greater than 1 for a compound? Justify your choice.

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CH342Fall 2011

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Report format for Purification of an Unknown Compound by Recrystallization

1. Title Page (Attach a separate Title page to your report)

A short descriptive title of the lab exercise.Dates the experiment was performed.Course and section numbers.Name(s)

2. Body of the report

Unknown compound number ________________

Results of solubility tests in the different solvents. Summarize the results in a neat table.

Solvent Solubility Result

Best recrystallization solvent found – explain

Weight of compound used for recrystallization __________________________

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Melting point range of unknown before recrystallization. ___________________

Weight of recrystallized unknown compound ____________________________

Melting point range of recrystallized unknown compound __________________

Calculate Rf value for all spots appeared on your TLC plate under UV light (Attach your TLC plate to your lab report)

Calculate the percent recovery of the unknown. Show your work.

3. Questions(a) What is the identity of your unknown solid? Explicitly explain your choice using the data you acquired (mp, TLC etc)

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(b) How do you know if the compound you recrystallized is pure? Explain.

Report format for Fractional Distillation

1. Title Page (Attach a separate Title page to your report)

A short descriptive title of the lab exercise.Course and section numbers.Dates the experiment was performed.Name(s)

2. Body of the report

You will receive your GC results either in the lab, or you can pick them up from your instructor later. We have a thermal conductivity (TC) detector on our GC. Use the correction factor for the TC detector to convert the peak areas to relative masses. Calculate the percentage by mass of cyclohexane and toluene in each fraction. Plot the component masses for each fraction on the y-axis as a function of the boiling temperature, using the midpoints of the appropriate boiling ranges on the x-axis: use different symbols for the different components. Draw a smooth curve connecting the points for cyclohexane, and another one for toluene: do not merely “connect the dots.” Turn in your gas chromatograms with your report.

3. Questions on page 84

Exercises 1

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Exercise 2

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Fractional Distillation Apparatus

Water In

Water Out (to sink!)

Transformer

Thermowell

Rubber Band

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CH342Fall 2011

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Report Format for Preparations of Synthetic Banana Oil 1. Title Page (Attach a separate Title page to your report) a. A short descriptive title of the lab exercise.b. Course and section numbers.c. Dates the experiment was performed.d. Name(s)

2. Body of the report a. Observations made during the reaction, and their meanings, if possible.

b. Weight of product isolated _____________________________

c. Boiling point range of product __________________________

d. Calculations of grams and moles of reactants. Show your work.

e. Calculations of theoretical and percent yields. Show your work.

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f. List your GC results in a tabular manner.

Peak# RT Area % Area

3. Exercises on page 78 Exercises 2

Exercise 4

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Banana Oil Gas Chromatogram

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Report Format for Dehydration of Methylcyclohexanols

Only collect 1 fraction of distillate, not two!

1. Title Page (Attach a separate Title page to your report)

A descriptive title with between 15-25 words.Course and section numbers.Dates the experiment was performed.Names.

2. Body of the report

Observations made during the reaction, and their meanings, if possible.

Weight of product isolated ________________________________

Boiling point range of product _____________________________

Calculations of grams and moles of reactants. Show your work.

Calculations of theoretical and percent yields of total methylcyclohexenes. Show your work.

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CH342Fall 2011

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List your GC results.

Your instructor will give you copy of IR and NMR of methylcyclohexanol and dehydration product(s) of methylcyclohexanol. Label all significant peaks on the IR and NMR spectra and attach the spectra to the report. Using IR and NMR result interpret success of your dehydration experiment carried out in the lab.

3. Questions on page 197

Exercises 2

Exercises 3

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CH342Fall 2011

Lab package

Oxidation of an Unknown Alcohol with Jones Reagent in Aqueous Media and on Silica Gel Support

In this lab you will oxidize isoborneol using two different methods and compare the results. These two methods are (a) classical Jones oxidation method and (b) a method developed by Dr. Mohammed Ali and his students in this department that utilizes silica gel supported Jones reagent.

A. Preparation of Silica Gel Supported Jones Reagent.

Weigh 4.0 gram of silica gel in a 50 mL round bottom flask. Add 1.5 mL of chromic acid (8M) to the flask drop by drop with stirring (use magnetic stirrer) using a syringe. Continue stirring until a free flowing orange solid is obtained. Your silica gel supported chromic acid is now ready for next step.

B. Oxidation of an Unknown Alcohol with Jones Reagent in Acetone.

Note: Jones reagent and methylene chloride are toxic. Follow safety procedure outlined by the instructor.

Weigh 1.5g of your unknown alcohol in a 250 mL Erlenmeyer flask. Add 50 mL of acetone to the flask and stir the content of the flask until solid dissolved. Add Jones reagent (8M) drop by drop with stirring until the characteristic orange color of the Jones reagent persist for several minutes (will require 3-4 mL of Jones reagent). Decant the acetone layer into another Erlenmeyer flask and rinse the green residue of the original flask with about 5 mL of acetone. Add the rinse to the acetone decant. If the color of the Jones reagent is visible in the acetone solution, add methanol drop by drop with stirring until the orange color disappear. Transfer the content of the flask into a 100 mL round bottom flask and remove the acetone using a rotary evaporator. Dissolve the residue in the flask in 10 mL of methylene chloride and transfer the solution into a 125 mL separatory funnel. Rinse the round bottom flask with a small amount of methylene chloride and add the rinse to the separatory funnel. Add 10 mL of a dilute sodium bicarbonate solution to the separatory funnel, stopper, and shake the funnel for a minute with periodically venting the pressure. Set the funnel on an iron ring and wait until the two layers separates in the funnel. Drain the bottom methylene chloride layer into an Erlenmeyer flask, save it and then discard the top aqueous layer. Return the methylene chloride solution back into the separatory funnel and shake it with a 10 mL of brine (saturated aqueous NaCl solution). Drain the bottom layer into a dry Erlenmeyer flask and add 2-3 spatula full of anhydrous sodium sulfate drying agent. Stopper the flask and wait for five minutes. Filter the solution through a funnel with a cotton plug. Rinse the drying agent with

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small amount of methylene chloride and add the rinse to the funnel. Transfer the filtrate into a 100 mL round bottom flask and remove the solvent using rotary evaporator. Determine the yield of the crude product. Determine purity of the crude product by TLC.

C. Oxidation of an Unknown Alcohol with Jones Reagent supported on silica gel.

Weigh 5.0 g of silica gel supported Jones reagent (0.4 mL of Jones reagent/g of silica gel) in a 125 mL Erlenmeyer flask. Add 20 mL of methylene chloride to the flask. Gently stir the content of the flask using a magnetic stirrer. Dissolve 1.5g of your unknown alcohol in about 5 mL of methylene chloride in a separate flask and add this solution to the Erlenmeyer flask containing the silica gel supported Jones reagent with stirring. Monitor the reaction by TLC. After the reaction is over, suction filter the reaction mixture and wash the solid with about 60 mL of methylene chloride. Transfer the methylene chloride solution into a 100 mL round bottom flask and remove the solvent using rotary evaporator. Weigh the product and determine the yield of the crude product. Determine purity of the crude product by TLC.

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Oxidation of alcohol lab report

Names _______________________ ______________________________

Date of Expt. ____________ Section ___________

Data Table

Procedure Amounts of theAlcohol used (g)

Amounts of JonesReagent used (mL)

# of mmoles ofJones reagent used

Product Yield(mg)

% Recovery

B

C

Questions

1. Which of the methods (B or C) is easier to carry out? Why?

2. Which method (B or C) produced higher yield? Suggest where loses might have occurred in the low yielding method.

3. Which of the two methods (B or C) has less potential to expose the person carrying out Jones oxidation reaction to the harmful reagents? Justify your answer.

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4. Which of the two procedures will you apply for alcohol oxidation in general? Why?

5. Collect IR spectra of your product from both procedures. Assign the significant peaks on the NMR (provided) and IR spectra and attach them to your lab report.

6. Was the oxidation of unknown alcohol complete in both the procedures? Justify your answer in terms of spectral data.

7. Suggest identity of your starting unknown alcohol using NMR data provided. Justify your choice.

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