CHEM 233A Fall 2005
Dr. Nooshin Hashemzadeh Phone:
Tue & Wed 1:00 am – 6:00 am mhashemz@whittier.edu
Required Supplies:
Carbon-copy laboratory notebook
Safety goggles
Apron
Disposable gloves (non-latex)
Text:
Mohrig, J.R.; Hammond, C.N.; Schatz, P.
F.; Morrill, T.C. Modern Projects and
Experiments In Organic
Mohrig, J.R.; Hammond, C.N.; Schatz, P.
F.; Morrill, T.C. Techniques in Organic
Grading
Grading, which will be curved, is based on experiments, quizzes, the final exam, and overall laboratory performance. Students who miss more than one lab will be dropped or given an incomplete ("I") grade.
The table on the next page is a point breakdown for Chem 233A coursework. Note that the lowest score for one experiment and one quiz will be dropped:
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9 Experiments 8 Quizzes Final Exam Performance Total |
30 10 |
270 (drop lowest) 80 (drop lowest) 100 50 500 |
Pre-Laboratory Work
You should read and understand both the theory and procedure of each experiment before performing any type of labwork. Pre-labs assignments, are to be completed in your laboratory notebook. Carbon copies of pre-lab work must be submitted to your instructor at the end of the lab period.
Post-Laboratory Work
Post-labs should also be completed in your laboratory notebook, and carbon copies of them are due one week after an experiment is performed. Late post-labs will be docked 5 points for each day they are late and will not be accepted after they are three or more days late.
Lab Notebook:
Carbon copies of all information entered into your notebook must be submitted to your instructor at the end of the lab period.
Final Exam
The final exam will be held on Wednesday December 7,2005, from 1:30 pm – 2:30 pm. The final is based on lecture notes, theory, quizzes and pre-lab questions and will not cover NMR/IR spectroscopy. The exam will be in Scantron format, so bring a #2 pencil (Scantron sheets will be provided).
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Exp. 1 Recrystalization |
Exp. 1 Recrystalization |
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Exp. 2 |
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Mp/TLC |
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Exp. 3 |
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Mp/TLC |
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Exp. 4 |
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Separation |
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Exp. 5 |
Exp. 5 |
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Separation |
Separation |
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Exp. 6 |
Exp. 6 |
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Stereochemistry |
Stereochemistry |
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Exp. 7 |
Exp. 7 |
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Distillation |
Distillation |
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Exp. 7 |
Exp. 7 |
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Distillation |
Distillation |
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Exp. 8 |
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Isolation |
Isolation |
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Exp. 9 DA Reaction |
Exp. 9 DA Reaction |
Thanksgiving |
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SCHEDULE OF EXPERIMENTS
EXP
#1 - Tuesday, September 13- Wednesday, Sep 14, 2005
Recrystallization of Salicylic Acid and Bromoacetanilide– (Read “Techniques..” pp. 78-92)
Supplementary information in Paula Y. Bruice (4rd ed): Chapters 1 & 2.
A. Recrystallization of Crude Salicylic Acid
Use the solubility data in -"Modern Projects and Experiments in Organic Chemistry (“Modern Projects”), Table 4.1 Solubility of Salicylic Acid in Water, page 25, to calculate the minimum volume of hot water needed to dissolve 100 mg of salicylic acid. By following the procedure in “Techniques..”, 9.7a on page 89, recrystallize approximately 100 mg of crude salicylic acid to obtain pure (as pure as you can) salicylic acid from hot water. Remember that the actual volume of water is just a little more than the calculated minimum volume. Record the initial and recovered amount (mass), and calculate % recovery. Submit your product in a vial with a proper label.
B. Recrystallization of Crude Bromoacetanilde
By following the procedure in “Techniques..”, 9.7a on page 89, recrystallize approximately 100 mg of a crude 4-bromoacetanilide containing small amount of 2-bromoacetanilide to obtain pure 4-bromoacetanilide from a mixed solvent pair [a 1:1 (v/v) aqueous ethanol solution]. Record the initial and recovered amount (mass), and calculate % recovery. Submit your product in a vial with a proper label and save it in the drawer to check it’s melting point in Exp #2.
Prelab Questions
1. Using Table 4.1 (page 25) in “Modern Projects..”, calculate the
minimum volume of hot water needed to recrystallize 100 mg of salicylic acid.
2. For question 1, calculate the amount of salicylic acid recoverable after the hot solution (above) was cooled to 0oC.
3. Calculate the % recovery when the recrystallization of salicylic acid is carried out by dissolving in minimum volume of hot water and cooling the water to 10oC.
4. The proper procedure for
recrystallization is to allow the hot solution to cool to room temperature,
then to chill the solution in an ice bath. Why do we not simply chill the hot
solution in an ice bath initially?
5. Explain whether or not each of the following pairs of solvents might be useful as a solvent pair for recrystallization. (See “Techniques..”, Table 9.1 and 9.2, pp. 80-83 and 9.2 “Selecting a Proper Recrystallization Solvent on pp. 81-82)
(a) ethanol-methanol
(b) hexane-cyclohexane
(c) acetone-ethanol
(d) water-ethanol
(e) water-cyclohexane
Postlab Assignment
Answer Questions 1-3 on p. 92 in “Techniques..”,
EXP
#2 - Tuesday, Sep 20- Wed, Sep. 21, 2005
Melting Points and
Thin-Layer Chromatography
Supplementary information in Paula Y. Bruice (4rd ed): Chapters 1 & 2.
Project 1:
Identification of a White Solid. Team Approach, pp. 239-241 in “Modern
Projects..”
First week Individual
Work, page 240 “Modern Projects..”
1. Determination of Melting Point of the Solid: Read “Techniques..” 10, pp. 93-103
Melting Points of an Unknown White Solid (“Techniques..” 10.3, pp. 98-101)
Determine the melting point of a white solid. Repeat the determination, if the two determinations do not check within 2oC, do a third one.
2. Analysis of the Solid
by Thin-Layer Chromatography (TLC): Read “Techniques..” 15, pp.153-162
3.
Solubility Test of the Solid.
Check the solubility of the solid in Water, Acetone, and 2.5 M NaOH.
Prelab Questions
1. What melting point range is typical for a pure compound?
2. To what depth should the capillary is loaded with sample?
3. When close to the melting point (within 15-20oC), how fast should you allow the temperature to rise?
4. Two substances, A and B, have the same melting points. How can you determine if they
are the same?
5. Why is it necessary to dry the recrystallized compound before taking a melting point?
Postlab Assignment
Answer Questions 1 on page 103 in “Techniques..”
EXP
#3 - Tuesday, Sep 27- Wed, Sep. 28, 2005
Melting Points and
Thin-Layer Chromatography (Continued)
Supplementary information in Paula Y. Bruice (4rd ed): Chapters 1 & 2.
Project 1:
Identification of a White Solid. Team Approach, pp. 239-241 in “Modern
Projects..”
Second Week: Team Work,
page 240 “Modern Projects..”
A. Check Melting Point of a Mixture (“Techniques..” 10.4, pp. 101-102)
Weigh roughly equal amounts (~5 mg each) of urea and cinnamic acid and grind the mixture finely with a spatula. Observe the differences between the melting points of pure urea, pure cinnamic and, and the mixture.
B. Determine the Identity of Unknown.
Identify your unknown
using “Techniques..” 10.3, 10.4, and
15.
Pre-Lab Questions
1. Why can there be no breaks in the thin-layer surface of a TLC plate?
2. Two compounds have the same Rf (0.87) under identical conditions. Does this show that they have identical structure? Explain.
Pre-Lab Assignment- Answer Questions 1 & 3, page 163 in “Techniques..”.
Post-Lab Assignment-
Answer Questions 1-4, page 241 in “Modern Projects..”
Exp. 4:
Separation of Organic Mixtures (Read “Techniques..” 8, pp. 56-77)
Supplementary information in Paula Y. Bruice (4rd ed), Chapters 1
Project 2. Using Extraction to Separate a Mixture,
pp. 243-246 in “Modern Projects..”
2.1 Separation and Purification of the Compounds in
the Unknown Mixture: First Week. Miniscale Procedure, page 244-245 in “Modern
Projects..”
2.2 Melting Points, purity, and Identification of
the Compounds in the Mixture: Second Week. Miniscale Procedure, page 245-246 in
“Modern Projects..” (Extra Credit)
Prelab Questions
1. Each of the following solvents is used commonly in the experiments to extract organic compounds from aqueous solutions.
a) methylene chloride (dichloromethane) b) hexane
b) toluene d) diethyl ether
Will the organic phase be the upper or lower layer when each of these organic solvents is mixed with water? Explain your answer for each situation.
2. Explain why the following solvents are not used in experiments that extract organic compounds from aqueous solutions.
a) ethanol b) acetone
Prelab Assignment
Answer Questions 1-5, page 78 in “Techniques..”.
Post-Lab Assignment
Answer Questions 1-4, and 6, page 246 in “Modern
Projects..”
EXP
#6 - A Dry-Lab Assignment is due by 5 PM Tuesday, Nov 25
STEREOCHEMISTRY:AN EXERCISE WITH MOLECULAR MODELS
HANDOUTs
Answer questions in the exercise packet. Exp # 5.
Supplementary information in Paula Y. Bruice (4rd ed), Chapter 5.
EXP
#7 - Monday, Nov 1- Friday, Nov 5, 2004
Boiling Points and Distillation (Read “Techniques..”
11.1-11.4, pp. 104-121. Apparatus Set-up in Fig. 11.6 (page 111) and 11.15
(page 120).
Supplementary information in Paula Y. Bruice (4rd ed), Chapters 1 & 2
- Simple Distillation
(Techniques 11.3, pp. 109-112)
Use the apparatus
shown in Figure 3.5 (use your 100 mL graduated cylinder to collect the
distillate, placing the mouth of the cylinder as far as possible into the
receiver-adaptor) to distill a mixture of 25 mL of cyclohexane and 25 mL of p-xylene. Ensure that the top of the thermometer bulb is positioned
midway in the opening to the condenser. Use a heating mantle supported on a
ring clamp to heat the flask to which has been added a clay boiling chip or
"Boileezer".1 Make sure that
the supporting ring clamp is above the level of the desk so that it may be
released and the heating mantle removed quickly in the event of any dangerous
overheating occurring. Also, be sure that the apparatus is not
"closed" to atmosphere; otherwise pressure will build up and possibly
cause an explosion.
Connect the mantle to
one of the themostats on the bench, and adjust the setting of the thermostat to
control the heat during the distillation so that the distillate drips slowly
and steadily into the receiver (about 1 drop per second). Use a graduated
cylinder to collect the distillate. Record the temperature every 2 mL as the
distillation proceeds until 45 mL of distillate are collected. (See below for
how to write this up in your book.)
Please note: This experimental setup is special in that it
uses a graduated cylinder to collect the distillate. This is not how distillations are normally carried out - one
normally uses a round bottom flask to collect with, so that loss of vapors is
minimized.
The boiling aid which
prevents "bumping" due to superheating, is an inert material with
small pores which provide sites where bubbles can form, thus inducing even
boiling. If, during a distillation, the temperature should drop below the
boiling point of the liquid in the flask, liquid will fill the pores and the
boiling aid will no longer be effective. In this event, the liquid can be
cooled and a fresh chip cautiously added. The new chip should not be added when
the liquid is at or near the boiling point, as this may initiate violent
boiling.
2. Fractional Distillation of an Unknown Mixture
(Technique 11.4, pp.118-121)
NOTE: Carry out the distillation in the hood.
Assemble the
apparatus shown in Figure 3.6; again use your graduated cylinder to collect the
distillate. (Only replace the steel wool in the condenser if it is severely
rusted)
Place a mixture
containing 25 mL of each of cyclohexane and p-xylene
in a 100 mL round-bottomed flask (dont forget some boiling chips!), connect it
to the fractionating column (Fig. 3.6) and proceed as described above. [NOTE that you will need to start the
distillation under fairly high heat, otherwise you will not finish on time.]
Again, record the temperature every 2 mL as the distillation proceeds until 45
mL of distillate are collected. Be sure
to increase the heating rate near the midpoint of the distillation otherwise
the head temperature will drop. (Why?)
Recording of Results (both Parts A & B)
Construct a table in
your notebook like that given below, to record the temperature at the
distillation "head" as a function of volume distilled. You will
record your data in both your and your partner's notebook simultaneously.
He/she will do the same.
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As the table is being
filled out, plot the boiling point vs. volume distilled for the distillation of
the cyclohexane/p-xylene mixture with
and without the fractionating column. Both sets of data will be plotted on the
same graph, using different symbols. Label the two curves.
In your notebook, comment on the following:
On the basis of your
results, which procedure was more efficient at separating the mixture into its
components?
From your results what generalization can you formulate about the purity of a liquid as judged by its boiling point?
Prelab Questions
1. Why do we add boiling chips or boiling stones before the distillation starts? Boiling chips
should never be added to a hot solution! Why?
2. Why would it be dangerous to heat a liquid in a distilling apparatus which had no vent or opening to the laboratory?
3. What is the effect on the boiling point of a solution (for example, water) produced by a
soluble nonvolatile substance (for example, sodium chloride)? What is the effect of an
insoluble substance such as sand or charcoal?
Prelab Assignment
Answer Question 3, page 132 in “Techniques..”
Post-Lab Assignment
1. Plot a distillation curve based on your experimental results for both simple and fractional distillation as shown in Fig. 11.14 (page 119) in “Techniques..”
2. Discuss the efficiency of simple and fractional distillations for separating the mixture.
EXP
#8 - Tuesday, Nov 15- Wed, Nov 16, 2004
Isolation of Essential Oils From Plants. (Read
“Techniques..” 11.7, pp. 129-132 & “Techniques..” 14 (Optical Activity and
Polarimetry), pp.140-149.
Supplementary information in Paula Y. Bruice (4rd ed), Chapters 5
Exp. 6.2 Isolation of (R)-(+)-Limonene from Orange
Peels,
Miniscale Procedure, p 44-46 in “Modern Projects..”
Steam Distillation, Isolation of Limonene, Isolation by HPLC
Prelab Questions
Answer Questions- 1-4, page 149 in
“Techniques..”.
Post-Lab Assignment
Answer Questions- 1, page 46 in “Modern
Projects..”
EXP
#9 - Tuesday, Nov 22-, Wednesday Nov 23, 2004
Project 9. Stereochemistry of Electrophilic Addition to An Alkene
Diels-Alder Cycloaddition Reaction of Dienophile
9.1 Synthesis of Cyclohex-4-ene-cis-1,2-Dicarboxylic Acid. Miniscale Procedure, pp330-331 in “Modern Projects..”
Supplementary information in Paula Y. Bruice (4rd ed), Chapters 8.
Prelab Questions
1. Write an equation for the reaction that occurs in the gas trap between SO2 and NaOH.
2. The reaction of fumaric acid with 1,3-cyclopentadiene gives
only one product. Explain why.
Post-Lab Assignment
Answer Questions- 1-2, page 334 and 1-3,
and 5, page 350 in “Modern Projects..”