Microsoft Word - CHEM2720-2021S-Project 3-information
Univ. of Guelph CHEM*2720 – Professor William Tam
1
CHEM*2720 Fundamental Organic Chemistry (Summer Semester 2021)
Project 3:
Virtual Lab – Hydrolysis of tert-Butyl Chloride
Due Date: June 26, 2021 (Saturday) by 11:30pm
(worth 4% of your final grade in this course)
1. Background:
For this virtual exercise we will explore the kinetics of the hydrolysis of t-butyl chloride. Our goal is to
understand how this experiment works, analyze the data, extract the rate constant and explore the effect
of temperature.
In this experiment 2-chloro-2-methylpropane (or tertiary butyl chloride) is reacted with water and the
kinetics are measured. This is a solvolysis reaction and provides excellent mechanistic insight into the
chemistry.
We begin by postulating that the reaction follows first order kinetics.
The HCl produced in this reaction is neutralized by the NaOH that is added to the flask at the beginning
of the reaction.
If our hypothesis is co
ect, then the rate of the reaction will be directly proportional to the
concentration of t-butyl chloride. Where k is the rate constant (with units of seconds-1):
Then:
Integration of the rate law over time gives:
Thus,
ln[tBuCl] = –kt + ln[tBuCl]o (y = mx + b)
Therefore a plot of ln[tBuCl] vs time should be a straight line with the slope of the line being equal to
the rate of disappearance of tBuCl.
Univ. of Guelph CHEM*2720 – Professor William Tam
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2. The Experiment:
Nine (9) experiments with varying amounts of each reagent will be performed according to the
following chart. Two replicates of each experiment are performed and the average is used for plots.
Run No.
Step 1: Prepare in a 50 mL flask Step 2: Add this and start timing!
0.01 M NaOH
(aq) solution
water
(contains
indicator)
0.1 M tBuCl
solution in
acetonitrile
acetonitrile
1 1 mL 7 mL 1 mL 1 mL
2 1 mL 7 mL 2 mL 0 mL
3 2 mL 6 mL 2 mL 0 mL
4 3 mL 5 mL 2 mL 0 mL
5 4 mL 4 mL 2 mL 0 mL
6 5 mL 3 mL 2 mL 0 mL
7 6 mL 2 mL 2 mL 0 mL
8 7 mL 1 mL 2 mL 0 mL
9 8 mL 0 mL 2 mL 0 mL
A sample procedure (for Run No. 1) is provided here for your information:
i) Use a burette to add 1.0 mL of 0.01 M NaOH to a clean, dry 50 mL Erlenmeyer flask.
ii) Use a burette to add 7.0 mL H2O (already contains the pH indicator) to the same flask.
iii) Add 1.0 mL of acetonitrile via Eppendorf pipettor. The solution should be yellow. Add 1
drop of extra indicator if not.
iv) When you are ready, dispense exactly 1.0 mL of the 0.1 M t-Butyl Chloride acetonitrile
solution into the flask. Swirl
iefly and START TIMING.
v) Watch for the colour to change from yellow to pink. Note the exact time taken for the colour
to change to the nearest whole second.
We are also interested in determining what relationship exists between temperature and reaction rate.
Using the volumes from Run No. 3, three extra experiments were performed. One was performed at
oom temperature, one in an ice bath, and the third in a hot water bath. The results for all runs are
tabulated together and posted p.5 for you to use in your report.
Here is a video that might help you understand the reaction:
https:
www.youtube.com/watch?v=RsFFYDe-kkk
Another useful link concerning “effect of temperature”:
https:
chem.li
etexts.org/Bookshelves/Physical_and_Theoretical_Chemistry_Textbook_Maps/Supple
mental_Modules_(Physical_and_Theoretical_Chemistry)/Kinetics/06%3A_Modeling_Reaction_Kineti
cs/6.02%3A_Temperature_Dependence_of_Reaction_Rates/6.2.03%3A_The_A
henius_Law/ XXXXXXXXXX
%3A_The_A
henius_Law_-_A
henius_Plots
Univ. of Guelph CHEM*2720 – Professor William Tam
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3. What do you need to do in Project 3 – Write a Report including the following information
Introduction:
Provide a
ief written description of the reaction being studied in this experiment and create an
original ChemDraw image depicting the mechanism/transition state. Provide an explanation as to
whether the reaction would be expected to go via an SN1 or SN2 mechanism and why, and provide the
expected rate law expression and order of the reaction. The introduction shouldn’t be longer than one
page single-spaced.
Results and Discussion:
1. Complete the following table, calculating the appropriate values:
XXXXXXXXXX
# mL of 0.1 M
tBuCl:
mixed with
# mL of 0.01 M
NaOH:
1.0
1.0
2.0
1.0
Molarity at the
start of
tBuCl (A)
and
NaOH (B)
0.01
0.001
0.02
0.001
End-point loss
of
tBuCl = B
(mol/L)
0.001
0.001
End-point
[tBuCl]
= (A-B) = C
(mol/L)
0.009
ln[C]
Time to colour
change (s)
See p.5
Room
Temperature
2. Plot ln[tBuCl] vs time (omit Run #1). Please use the computer graphing software of your choice
and insert the plot as an image into your report.
3. Calculate the value of the rate constant k.
4. Did the reaction follow the mechanism you suspected? Explain:
a. Whether runs 1 and 2 demonstrate the validity of the rate law (why or why not?)
. What do runs 2 and 3 demonstrate with respect to the rate law’s dependence on the
concentration of OH-?
c. Why run 1 isn’t included in the plot
d. Why the initial [tBuCl] is constant for runs 2 through 9
Univ. of Guelph CHEM*2720 – Professor William Tam
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5. What is the relationship between the colour change and the pH, and what does it tell you about
the reaction taking place?
6. Calculate the time required for the reaction to be 78% complete.
7. How does temperature affect the experiment? Recall the A
henius equation. What value(s) can
this plot provide? What additional experimental work would you need to do in order to make an
A
henius plot for this experiment?
8. Would you expect the hydrolysis of tBuBr to be faster or slower? Suggest why.
Hint: Your graph for question 2 should look similar to this one, but should show an equation for the
line of best fit, please!
XXXXXXXXXX500
-4.35
-4.30
-4.25
-4.20
-4.15
-4.10
-4.05
-4.00
-3.95
Data points 2 to 6 !!
DATA1B
L
n
[
t-
B
u
C
l]
a
t c
o
lo
u
ch
a
n
g
e
Time (seconds)
Figure X. Good title for plot goes here!!!
4. How to submit your work of Project 3:
Submit your report (typed, drawings by ChemDraw) in ONE single MS Word file (or pdf file).
Submit your MS Word (or pdf) file through "Crowdmark" using the following link:
https:
app.crowdmark.com/sign-in/guelph (See CourseLink “Announcements” for details how to
access and use Crowdmark).
**Any suspicion of copying from the web or a friend will result in an automatic grade of zero until
you demonstrate authorship. Please don't be lazy and do your own work.
Univ. of Guelph CHEM*2720 – Professor William Tam
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Here are the data you need to complete the report
Date set that you have been assigned to use:
Students with the last digit of
your student number ENDING with:
Data Set
0 A
1 B
2 C
3 D
4 E
5 F
6 G
7 H
8 I
9 J
Data Sets: (The values are time in seconds to the colour change.)
Data
Set
Run number Effect of Temperature
XXXXXXXXXX
3 (hot)
at 35°C
3
at 21°C
3 (cold)
at 0°C
A XXXXXXXXXX XXXXXXXXXX95
B XXXXXXXXXX XXXXXXXXXX86
C XXXXXXXXXX XXXXXXXXXX76
D XXXXXXXXXX XXXXXXXXXX76
E XXXXXXXXXX XXXXXXXXXX74
F XXXXXXXXXX XXXXXXXXXX76
G XXXXXXXXXX XXXXXXXXXX95
H XXXXXXXXXX XXXXXXXXXX88
I XXXXXXXXXX XXXXXXXXXX74
J XXXXXXXXXX XXXXXXXXXX72
**A tutorial via Teams will be given after the 1st Midterm exam to explain the above information and
data, and I will give you more advice on how to complete and do well in this project. Make sure to
attend the tutorial (or watch the recorded tutorial). See CourseLink for details.