Guidelines for Lab Reports
Learning how to effectively
report experimental results is extremely important in
all of the sciences. Although the customary format may
vary between discipline, a scientific report should be
clear, thorough, concise and well organized and should
make effective use of tables and graphs.
Formatting
- Reports should be word-processed and
double-spaced.
- Do not ignore the need for subscripts
and superscripts in chemical formulas. These are
easily available in all modern word processors.
- Use a minimum font size of 11 and left
and right page margins of 1.0".
- For chemical
structures it is not acceptable to copy and paste
graphics from web sources. There are a variety of
free structure drawing programs available (see the Chem 351 Links page) and
neatly hand-drawn structures are acceptable for the
purposes of this course.
Conciseness - Strive to make your
report as concise as possible. A page limit of 12 pages
(not counting attachments) applies to all lab reports.
(Please number the pages!)
- In achieving conciseness, it is
important that you use standard abbreviations and/or
chemical formulas (when unambiguous) in place of full
chemical names. For example write "MeOH" instead of
"methanol", CDCl3 instead of chloroform-d,
and C6H6 instead of benzene. (However, do not use formulas as
stand-ins for names when the formula is complex
enough to have many isomers possible, i.e. C9H8O2
is not an acceptable abbreviatioin for trans-cinnamic
acid.)
- All measurement units have standard
abbreviations and these should always be used in
conjunction with the numerical value for the
measurement, e.g. always write "15 cm" not "15
centimeters" or "fifteen centimeters".
- Here is a spreadsheet with
commonly needed standard abbreviations. Remember to
use these freely and to not waste space defining them.
- Also consider creating your own
abbreviations to replace long compound names. Most preferably use bold numbers
(e.g., 1, 2, 3) to represent
each compound. Define these simply by placing
parentheses immediately after the first instance of
the full compound name in the report. See example
below:
"1,4-Di-tert-butyl-3-iodobenzene
(1) was reacted with 4-tolylboronic acid (2)
with the intent of forming the coupled product,
1,4-di-tert-butyl-4-tolylbenzene (3).
The crude yield of 3 was 0.76 g (23% based
on 1)."
Data Interpretation - Students are encouraged to bring
rough drafts and questions about data interpretation to
the instructor prior to submitting their final report.
Report Organization - Include all
of the following sections.
Title Page - Give the number and title of the experiment,
your names, course number and section, and the date
submitted.
Purpose - Give specific
information on the reaction being carried out including
chemical equations showing structures of all reactants
and products.
Mechanism - Present and discuss the
accepted mechanism for the reaction carried out. Make
sure to use equations/structures/curved arrows as
necessary to show the mechanism properly.
Results Tables Present all of the results of the experiment
in table form. (The
results tables can either be grouped all together in
their own separate section or they can be interspersed
where appropriate throughout the Results and
Discussion.)
- Table Organization and Style
- Each results table should be
completely self explanatory. In other words, it
should be easily and fully comprehensible on its
own even if viewed separately from the rest of the
report.
- Number and title the tables. The
title should give fairly complete information
about the data contained in the table. The number
facilitates referring to the table in the Results
and Discussion section.
- Include structures
of the compounds as part of the table title;
immediately beneath the title place labeled
structures that further clarify the contents of
the table.
- Strive to make tables very concise
and "non-wordy". If at all possible keep each
table confined to a single page. This well require
a well thought out organization scheme for each
title.
- Make sure to observe the
significant figures convention! Significant
Figures Tutorial
- Use footnotes as necessary to fill
in missing details or to give definitions of
abbreviations used in the table.
- Table Contents
- Yield data.
- Include the absolute yield
(mass), theoretical yield, and percent yield
(rounded to the nearest whole number) of any
product obtained. Do not include tare masses.
(Show the calculation of theoretical and percent
yield on an attachment not in the
table.)
- Physical Constants.
- Melting points. Include the mp
range for every crystalline solid product.
- Other physical constants. These
include refractive index and boiling point
determinations.
- Literature values. Include
literature values for any physical constants
measured.
- Units. Make sure to give units
where required. (A well-organized table gives
the units in the column headings or in the
title rather than repeatedly throughout the
table.)
- Spectroscopic data. Use tables to
summarize all spectroscopic data (NMR, IR, MS)
obtained.
- IR.
Round peak frequencies to the nearest 1 cm-1.
Describe each peak as vs (very strong), s
(strong), m (medium), w (weak)
- MS.
Round peak m/z values to the
nearest whole number. List the approximate
percent abundance of each peak (as
compared to the base peak).
- C-13
NMR. Round peak shifts to the
nearest 0.1 ppm except when greater
precision is needed to distinguish
closely spaced peaks.
- H-1 NMR.
Round off peak shifts to the nearest
0.01 ppm. Make sure to
also state the multiplicity and integration
value of each peak.
- Literature values.
- Include literature values of
chemical shifts, wave numbers, and m/z
when available. Use a superscript number to
cite the reference. (See the part on
references below)
- Peak assignments
- For NMR the assignment
should be a letter that refers to a labeled
chemical structure included with the table.
- For IR the assignment should
refer to the specific type of bond vibration
and the functional group family,
e.g., C=O (ketone), C=O (anhydride), O-H
(alcohol).
- For MS, the assignment can
take form of describing the neutral fragment
lost, e.g. M - CH3, M - Br, or
preferably show the structure of the cation
detected
- Results and Discussion
- This section is referred to as
"Results and Discussion" because the proper way to
go about it is to state some results and then go
on to discuss them.
- Make sure to actually state the
results to be discussed rather than just refer to
a table. For example, even though your Table 1
might show the observed and literature mps for
your product, your R&D part should start out
as, "The mp of the product was found to be XX in
comparison to the literature value of XX. (Table
1)"
- After stating the results, go on
to explain your interpretation as to how they
align with the theory behind the experiment.
- Make liberal use of
structural diagrams, equations, curved arrows,
images of molecular models, etc., to
illustrate points being made as appropriate.
- For puzzling results that do not
seem to fit the theoretical expectations, are
there valid explanations for them? Are they
erroneous (due to systematic experimental error)
(identify the specific reason for the systematic
error if you think it is present). If you can rule
out systematic error then examine how the theories
could be modified to accommodate the results.
- This section should include
answers to the assigned questions. Make sure to
explain all answers completely even if the
question does not ask for an explanation.
- Above all, make sure your answers
and interpretations make sense! Do not just take a
stab at interpreting the results! If uncertain, do
some Internet and/or library research or ask the
instructor if you are on the right track.
- For synthesis experiments always
discuss:
- Yield - Actual yield of product
versus the theoretical yield (percent yields)
and possible reasons for loss of yield. Please
see this page for more info: Yield Reporting and
Discussion
- Spectra Interpretation -
Evidence for the structure of the product from
NMR, IR and/or chemical tests.
- Purity - Purity of the product
as indicated by mp, bp, NMR, etc. Identify
impurities that are present if possible,
explaining thoroughly the reasoning behind your
conclusions.
- Conclusions
- Reiterate the main
points from your results and discussion sections
in very brief form. Ideally, you can boil down the
experiment to four or five main conclusions, each
stated in one or two sentences.
- Give actual data
again in this section to support each conclusion.
The data can be concisely included simply by
providing it in parentheses at the appropriate
places within the text.
- Comment on whether
the experiment was successful or not and feel free
to make suggestions as to how the experiment could
have been better designed or carried out.
- Please notice that
the title of this section is "Conclusions" not
"Conclusion". It is not meant to to be a typical
"wrap up" paragraph that starts out. "In
conclusion, we carried out...etc". Instead it is a
very concise list of the main points to be taken
from the results obtained.
- Experimental
Section
- This part
describes the procedures that were used in very
concise form. Use past tense, passive voice and
list the results obtained in sentence form at
the end of the paragraph. See any recent article
in the Journal of Organic Chemistry for an
example of how to write this part.
- References
- Give sources for all literature
values as well as for any other background
information.
- List the references in the order
they are cited in the report and give each
reference its own number. Cite references in the
main body of the report using superscripted
numbers.
- Use ACS style for your references
list. See http://courses.chem.psu.edu/chem431/ManuscriptFiles/QuickRefGuide2.pdf
- Attachments
- Calculations - An example
of each non-trivial calculation, including % and
theoretical yield calculations, should be
shown. Do not include trivial calculations
such as subtraction of tare weights.
- Spectra - Attach printouts
of all spectra obtained. Make sure the spectra are
completely labeled (name, date section number,
expt number and title). Label all peaks on the NMR
spectra. By labeling all solvent peaks and other
expected extraneous peaks (e.g., TMS, water) you
make clear what they are without unnecessarily
devoting lab report discussion to them. For IR and
Mass spectra it is not necessary to label small
unidentifiable peaks especially those in the
fingerprint region of the IR.
Product Submission - Products are
ordinarily submitted for grading and then proper
disposal. Submitted products should be fully labeled
with the compound name and structure, your name,
experiment number, and course number.
- Solid products should be placed in
small disposable vials (not conical vials!).
- Liquid products should be placed in
screw-top vials (not conical vials or reaction
flasks).
Team Contribution Surveys (TCSs) - These
are made available on D2L the same day the lab report is
due for each experiment. They are due within one week of
the lab report submission.
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