Rxn notebook, lab setup, and lab write up

University of Washington – TacomaOrganic Chemistry I (TCHEM 261)
Compound ID Lab – Revised W23
StudentVersion
INTRODUCTION
Chemists often wish to determine the identity of an unknown compound. Traditionally
they did this by using a series of chemical tests, derivatizations, and determination of physical
properties. These tests are still useful, but chemists now also have available a powerful array of
spectroscopic tools: Mass Spectrometry (MS), Infrared Spectrometry (IR), and Nuclear Magnetic
Resonance Spectroscopy (NMR). UWT has both IR and 1H-NMR spectrometers available for
student and research use.
This lab has an urgent objective. An illegal dump was found in east Pierce County with
about 64 unlabeled drums filled with organic compounds. The Pierce County Environmental
Services Division has asked the UWT chemists to identify the unknown compounds in these
drums so that they can be safely reused or disposed. Each lab group needs to determine the
identity of two unknowns, one solid and one liquid. To accomplish this task, students will obtain
IR and 1H-NMR spectra of their unknowns. They will also determine melting and boiling points
and other physical constants such as density and refractive index. If desired, students may
request a mass spectrum and/or 13C-nmr spectrum. Reagents needed to carry out some
potentially helpful chemical tests will also be available, and students may perform these tests at
their discretion. If students are unable to identify their unknowns, elemental analysis can be
requested, but this will result in a deduction of points.
When a chemist is faced with identifying an unknown chemical compound, there is a
systemic approach often used. The following story about Harold and Erma and Unknown X
illustrates a common approach, but not the only possibility.
Sample of Steps in Identifying an Unknown.
Organic Chemistry students Harold and Erma investigate solid Unknown X. It is a solid,
so they take its melting point (m.p. = 60-62 oC). They next take an IR spectrum (shown in
Figure 1 below), as IR is good for determining the presence or absence of major functional
groups in a compound.
Figure 1: IR spectrum of Unknown Solid X.
Harold and Erma decide that the strong peak at 1700 suggests the presence of a carbonyl
group. The lack of an –OH peak above 3000 rules out a carboxylic acid. The weak peaks
above 3000 suggest the possibility of an aromatic group, while the strong signals just below
3000 indicate at least some aliphatic hydrogens. At this point, Harold and Erma suspect that
they have either an aldehyde, a ketone, or an ester which contains both aromatic and aliphatic
groups.
Harold and Erma then obtain the 1H-NMR spectrum shown below.
By studying this 1H- NMR, Harold & Erma determine that the compound contains 9 aromatic
and 3 aliphatic Hydrogens. A 13C-NMR tells them that the compound has 10 unique carbons.
From this information, they write 3 or 4 possible structures, and check melting points of the
possible structures. One matches. This proposed structure has a methyl group, so they run the
iodoform test and it is positive, confirming their proposed structure. They turn in this structure
and are thrilled to receive an “A” for this lab.
The moral of this example is “Be like Harold and Erma.” Use a logical, step-wise approach to
identifying your unknowns, chose your tests wisely, and be sure to consider ALL the data.
This is a Three-Week Lab for Winter 23
PREPARATION for Week 1
1. Read the Whole Lab. Note that you will be writing a complete lab report for this lab.
2. Learn or Review any concepts or skills you are not confident about applying during lab. Note:
We will be covering IR and NMR and Mass Spec in lecture; you do not have to teach
yourself the topic. This is, however, a great time to read ahead. You should also review
melting points and boiling points.
Melting points: Nichols 6.1D
Boiling point determination: Nichols 6.2A, Thiele Tube method
https://chem.libretexts.org/Bookshelves/Organic_Chemistry/Organic_Chemistry_Lab_Technique
s_(Nichols)/06%3A_Miscellaneous_Techniques/6.02%3A_Boiling_Point/6.2B%3A_Step-byStep_Procedures_for_Boiling_Point_Determination .
IR: Smith Spectroscopy B
1
H-NMR: Smith Spectroscopy C
3. Prepare your lab notebook as described below.
LAB NOTEBOOK Set-Up Week 1
• Title – Use the one given for this lab.
• Clerical Information – Your name, the name of your assigned lab partner for that lab,
and the date on which the in-lab work was started. Be sure to also enter the lab in your
Table of Contents.
• Objective – After reading the entire lab, identify and write down the objective of the lab.
The objective is the question or questions your data will hopefully allow you to answer.
• Hypothesis – For Week 1 of this lab, please write a hypothesis about how useful melting
points and boiling points will be for helping to determine which functional groups your
compounds contain.
• Physical & Chemical Properties Table – You do not need to do any Material Data &
Safety/hazards table for this lab, as all of our compounds are unknown. HOWEVER,
remember that these compounds are organic, and thus likely to be flammable, toxic,
irritants, corrosive, and/or mutagenic. Wear gloves and perform transfers in the hood.
• Safety – List any particular safety issues associated with this lab.
• Pre-lab questions: None for Week 1
1. What is the objective of this lab?
•
•
Experimental Plan – Use the Experimental directions below to write a plan for the work
you need to do in Week 1’s lab session
Data – Create spaces in your notebook to record all the data you will collect.
PREPARATION for Week 2
LAB NOTEBOOK Set-Up Week 2
• Clerical data, especially date, name, and partner’s name.
• Hypothesis – For Week 2 of this lab, please write a hypothesis about how useful H-NMR
will be for helping to determine the types of hydrogen atoms present in your compounds.
• Pre-Lab Questions Week 2 – Do on separate sheet, not in Lab Notebook
1. During last week’s lab, Harold and Erma started by taking a melting point of their
solid, unknown X. However, when interpreting their data, is the melting or
boiling point of the unknown going to be the piece of data that they use first to
begin to identify the unknown? Explain.
2. What did the IR spectra tell you about your solid?
3. What did the IR spectra tell you about your liquid?
•
•
Experimental Plan – Use the Experimental directions below to write a plan for the work
you need to do in Week 1’s lab session
Data – Create spaces in your notebook to record all the data you will collect.
PREPARATION for Week 3
LAB NOTEBOOK Set-Up Week 3
• Clerical data, especially date, name, and partner’s name.
• Hypothesis – For Week 3 of this lab, please write a hypothesis about how useful Mass
Spec will be for helping to determine the types of functional groups present in your
compounds.
• Pre-Lab Questions Week 3 – Do on separate sheet, not in Lab Notebook
1. During last week’s lab, you obtained H-NMR spectra. Copy the following table
twice and fill it in once for your liquid unknown and again for your solid
unknown.
Chemical
Shift
Area
Relative Possible
Area
# of H
Observed
Splitting
# of
Neighbors
Possible types of H
2. What possible structures or structural fragments are suggested by your H-NMR?
3. Harold and Erma started by taking a melting point of their solid, unknown X.
However, when interpreting their data, is the melting or boiling point of the unknown
going to be the piece of data that they use first to begin to identify the unknown?
Explain.
Experimental Directions
The following steps do not need to be done in a particular order. Your instructor will
guide you in proceeding in a manner that will prevent long waits for a certain piece of
equipment.
WEEK 1
Melting Point of Solid Unknown
Determine the m.p. of your solid unknown using the Mel-Temp apparatus.
Boiling Point of Liquid Unknown
An apparatus for determining boiling point is shown in this link
https://www.google.com/search?q=boiling+point+apparatus&safe=active&biw=1413&bih
=620&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0ahUKEwiHhd2L_4fLAhVB3W
MKHc_nAfkQsAQIGw&dpr=0.95#imgrc=fJYDX3FBOGQ37M%3A
Or this one.
https://www.google.com/search?q=boiling+point+apparatus&safe=active&biw=1413&bih
=620&tbm=isch&tbo=u&source=univ&sa=X&sqi=2&ved=0ahUKEwiHhd2L_4fLAhVB3W
MKHc_nAfkQsAQIGw&dpr=0.95#imgrc=tEAiUbIiemhfWM%3A
Place a small quantity of the unknown liquid in a little test tube. Invert the open end of a closed
end capillary tube in the test tube. Rubber band the test tube to a thermometer. Place the test tube
(but NOT the rubber band) in a cool oil bath. Heat until bubbles come out of the mouth of the
capillary tube. Turn off the heat and cool. Watch for the temperature at which liquid is sucked
back into the capillary tube. Record these two temperatures as the b.p. range.
IR Analysis
Run an IR on each of your unknowns. Dan or Dr. Meg will be available to assist you. Make
sure you clean the instrument after use. You should analyze the spectrum obtained from your
compound. Be sure to include the spectrum in your post lab submission.
WEEK 2
1
H-NMR Analysis
Prepared NMR samples will be available for each unknown. The lab staff made these by
dissolving enough of each sample in 0.5 mL of deuterated solvent to create a 0.5 M solution. A
drop of TMS was added to your sample. The instructor will show you how to run our NMR
spectrometer.
13
C-NMR will be provided.
WEEK 3
Mass spec will be provided.
Based on the information obtained from the IR and NMR, consider running any of the following
chemical tests. If you think you wish to do any of these tests, please talk to the instructor about
how to carry them out.
Additional Physical Tests
Density determination of a liquid
Refractive Index
Optical Rotation
Solubility
Fluorescence
Possible Chemical Tests
Bromine Test
Cold dilute KMnO4 test
Alcoholic Silver Nitrate Test
FeCl3 test
Tollen’s Test – aldehydes & some ketones
Iodoform Test – methyl ketones
pH
University of Washington – Tacoma
Organic Chemistry I (TCHEM 261)
Compound ID Post-Lab: Formal Lab Report
You will write a complete formal lab report for this lab. See general
directions posted on canvas in the scientific writing module. I also
suggest that you read the grading rubric both prior to writing your
report and again before you submit your final draft.
Compound ID Lab Report Rubric
Criteria
Evaluation
ABSTRACT
States purpose of work/
problem being investigated.
Hypothesis stated
Major methodology stated
Key result(s) stated
Major outcome given
INTRODUCTION
P1: Background & context
P2: Objective/ Hypothesis/
Proposed work
P3: Results & Implications
EXPERIMENTAL
The lab work for each of the following should be described in
sufficient but not excessive detail. This section must be written in
the past tense and passive voice.
Physical constant
determination
IR
NMR
Chemical tests
RESULTS
Measured Physical constants
given
IR – spectra attached with
labelled peaks.
H-NMR
– spectra attached.
Possible Awarded
Points
Points
10
2
2
2
2
2
12
4
4
4
10
2
2
2
2
2
18
2
4
8
– Table of signals with shift, splitting,
areas included – see examples.
MS, 13C-NMR, other tests
4
DISCUSSION
The discussion is your chance to make a strong argument for your proposed
identity of each of your compounds. Build an argument that will convince your
reader that the unknown is what you propose it is. Refer to data using Figure
and Table numbers so that your reader can look at the data you are
discussing. Be sure to comment on ALL the data you have for a compound –
don’t cherry-pick!
Solid compound ID
• Discusses information that can
be deduced from each piece of
data
• Builds a cohesive, logical
argument
• Discusses any anomalies
• Nothing overlooked
20
2
2
4
2
2
4
Liquid compound ID
•
•
•
•
•
•
Physical constants
IR
H-NMR
Other spec. if used
Chemical tests if app.
Conclusion
Conclusion and
Recommendations to the
Pierce County Environmental
Services Team
Mechanics
*Typed, double –spaced?
*Complete sentences?
*Understandable
grammar, punctuation &
spelling?
*References/citaitons
Quality
* Logic
* Connections, flow
* Effort
TOTAL
20
2
2
4
2
2
4
4
6
1
1
2
2
4
100
You will also receive a grade (25 pts) based on your in-lab work. This grade will include
notebook preparation, pre-lab quiz score, understanding of the tests you are running,
care and gentle treatment of our equipment, teamwork, tidiness & cleanliness, safe
handling and proper disposal of chemicals, and general attitude.