Organic Chemistry Synthesis of Tert Butyl Chloride Labs & Practice Problems

CHEM 2010Laboratory
SN1 Synthesis of tert-Butyl Chloride
Alkyl halides can be prepared from their corresponding alcohols via a substitution reaction. The
mechanism of these substitution reactions are labeled as SN1 (substitution, nucleophilic,
unimolecular) and SN2 (substitution, nucleophilic, bimolecular). Tertiary alcohols follow the SN1
route, primary alcohols follow the SN2 route, and secondary alcohols can follow either path.
This experiment focuses on the SN1 reaction between t-butanol and hydrochloric acid to produce
t-butyl chloride.
Figure 1: Conversion of t-butanol into t-butyl chloride with hydrochloric acid
The product will be verified by gas chromatography by comparing the chromatogram of the
synthesized product to provided chromatograms of t-butanol, and t-butyl chloride. Confirmation
of your product, tert-butyl chloride, can also be performed by reacting the product with a
solution of silver nitrate in ethanol. The appearance of a precipitate indicates a positive result for
the presence of an alkyl halide.
OBJECTIVES
In this experiment, you will
• Synthesize tert-butyl chloride via an SN1 reaction.
• Confirm the presence of a tertiary alkyl halide using the silver nitrate test.
• Verify the product by gas chromatography.
READING
•
•
•
Textbook material on Substitution reactions
Read all 8 sections Extractions: 4.1 – 4.8.
Read about the Silver Nitrate Test
TECHNIQUE VIDEOS
•
Watch Separating Components of a Mixture by Extraction; Liquid / Liquid Extractions;
and Drying of Organic Liquids
Adapted from: Organic Chemistry with Vernier
Page | 1
SN1: Synth of t-BuCl
READING & VIDEO QUESTIONS
1. Why would extraction be chosen as the method to separate mixtures?
2. In order for an extraction to be successful, what is the one major factor of the liquids used
in the extraction that has to be considered and followed? Both liquids must be
___________. Explain why.
3. Name and describe 3 uses for extraction.
4. What should always be done before adding any of your reaction liquids to a separatory
funnel? (Video 2.)
5. Describe 2 ways to determine which layer is which in an extraction.
6. The bottom layer should be drained out of the bottom of the separatory funnel and the top
layer should be poured out of the top of the funnel. Why? What would happen if you
drained both layers out of the bottom of the funnel? (Video 2.)
7. Why would a multiple extraction method be the technique to use?
8. Define emulsion.
Adapted from: Organic Chemistry with Vernier
Page |2
SN1: Synth of t-BuCl
9. Name and describe 3 common solutions used for reaction workups. Explain why each is
used.
10. What are drying agents used for? Name 3.
11. What types of reactions are utilized to transform organic compounds, that are soluble in
the organic layer, so they become soluble in the aqueous layer?
12. How do you know you have added enough drying agent? (Video 3)
13. Consider the silver nitrate test.
a. What does this test indicate is present?
b. What would constitute a positive test?
c. What is the precipitate seen in a positive silver nitrate test? ________________
d. What results would you expect to see if silver nitrate reagent solution was added to
a solution containing the reactant of this experiment only?
e. What results would you expect to see if silver nitrate reagent solution was added to
a solution containing the product of this experiment only?
Adapted from: Organic Chemistry with Vernier
Page |3
SN1: Synth of t-BuCl
PRE-LAB EXERCISES
1. Complete the table below.
Compound
Molar mass
(g/mol)
Density (g/mL)
Melting point (°C)
Boiling point(oC)
tert-butanol
tert-butyl chloride
Literature
Reference(s)
2. Draw the complete reaction mechanism for the reaction performed in this experiment.
3. Write out the balanced chemical reaction occurring during the sodium bicarbonate wash
step. Why is it important to swirl before beginning the shake and vent portion of the wash?
4. What is the theoretical yield of tert-butyl chloride if 5.00mL of tert-butanol was reacted
with excess hydrochloric acid?
Adapted from: Organic Chemistry with Vernier
Page |4
SN1: Synth of t-BuCl
5. You will analyze the purity of your product using GC. Below are the GC’s for pure
reagent samples of t-butanol and t-butyl chloride. Complete the data table below using
the information contained in the pictures below. The numbers in the bottom left of each
picture are the location of the blue cursor on the chromatogram.
Compound
Retention time
(min)
tert-butanol
tert-butyl chloride
Adapted from: Organic Chemistry with Vernier
Page |5
CHEM 2010
Take-home Laboratory Exam
Fall 2022
Name: ________________________
Answer each question in a concise yet thorough manner.
1. What is the primary purpose of doing a melting point study on a sample? What is the
key information that can be learned from the results?
2. What is the primary purpose of doing a TLC study on a sample? What is the key
information that can be learned from the results?
3. What is the primary purpose of doing a GC study on a sample? What is the key
information that can be learned from the results?
4. Provide a mechanism for the following SN1 reaction.
OH
HBr
Br
5. During the work-up of many reaction mixtures the extract is washed with a saturated
aqueous solution of sodium chloride. What is the purpose of this step?
CHEM 2010
Take-home Laboratory Exam
Fall 2022
6. Consider the GC spectra of a pure sample of MTBE
Explain how the spectral result would be altered if each of the following changes were
made to the technique or experimental conditions.
a. The pressure were increased from 7kPa to 12 kPa?
b. The initial temperature were dropped from 60oC to 40oC?
c. The MTBE is mixed with an equimolar amount of a compound with a much
higher melting point?
d. Decrease the sample size injected from 0.2 microliters to 0.1 microliters.
CHEM 2010
Take-home Laboratory Exam
Fall 2022
7. A student was tasked with identifying a set of five unknown samples, labeled as A-E. It is
known that some of the samples are of the same compound, while some may be unique
to the rest. To determine which are the same and which are unique, a mixture melting
point study and a TLC study were done.
a. Analyze the melting point data and list key observations pertinent to identifying
any samples as being the same compound.
Observed Melting Point
Range (oC)
60-72
65-76
69-71
64-75
129-136
125-134
129-137
142-150
152-153
61-69
Mixture (90/10)
A/B
A/C
A/D
A/E
B/C
B/D
B/E
C/D
C/E
D/E
a. Analyze the TLC data provided below. Record the Rf values for A, B, and C.
Sample
A
B
C
Rf value
TLC plate:
A
B
C
D
E
A/B
E/C
A/B/D
b. Combine what you learned from both sets of data to predict what would be seen
in the TLC of compounds D and E as well as the mixtures described in each
column.
CHEM 2010
Take-home Laboratory Exam
Fall 2022
8. We identify the unique compounds within a sample as spots on a TLC plate when
viewed under a UV light. How does this work?
9. If you run a TLC plate in a 4:1 mixture of ethyl acetate/hexane and all of your samples
have Rf values less than 0.3, would you be satisfied with these results? What changes
would you make to improve your results?
10. Determine the expected GC elution order for the following mixture from a GC mini and
sketch the anticipated spectra based on all data given. Label axes and each peak in your
chromatogram.
Compound
A
B
C
Boiling Point
101
36
165
Percent Abundance
10
60
30
11. Draw a well-constructed chromatography column like that used for our spinach
experiment. Label each item used and explain the purpose of each item clearly.
at
par
Hi
_oI
CHEM 2010
Take-home Laboratory Exam
Fall 2022
12. Consider the absorption spectra results below. Note that there are three samples
plotted on this same spectra.
a. Identify the sample you suspect to be red, and label as A. Explain your logic.
b. Identify the sample you suspect to be blue and label as B. Explain your logic.
c. What color would you suspect to observe for the remaining sample? Explain
your logic.
Iaukea