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".
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 where
unambiguous, in place of full chemical names. For
example write "MeOH" instead of "methanol" and CDCl3
instead of chloroform-d.
- 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.
Organization - The lab report should include each
of the following parts in the order listed.
- 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. 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.
Also be sure to:
- Make your tables as concise and as well organized
as possible.
- If at all possible keep each table confined to a
single page.
- 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 your results and
discussion section.
- Include structures of the compounds with the
tables.
- Include the absolute yield (mass), theoretical
yield, and percent yield (rounded to the nearest whole
number) of any product obtained. (Show the calculation
of theoretical and percent yield on an attachment not
in the table.)
- Include the melting point range for every
crystalline solid product.
- Include literature values for any physical constants
measured.
- 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.)
- Include summaries (i.e., peak listings) of any
spectroscopic data (NMR, IR, MS) obtained.
- Round off IR frequencies to the nearest 1 cm-1
and MS peaks to the nearest whole number m/z
value. C-13 NMR peak shifts should be rounded off to
the nearest 0.1 ppm except when greater precision is
needed to distinguish closely spaced peaks.
- Do not include solvent peaks (e.g., CDCl3)
in NMR tables.
- Do include literature values of chemical shifts,
wave numbers, and m/z when available.
- For NMR, IR and MS tables you should include a
column for "peak assignment".
- 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
- 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.
- Also use footnotes to give references for literature
values. (Refer to each reference by its number in your
report-end list of references. For example a table
footnote might typically read, "See reference 3.")
- Results and Discussion
- Start by presenting key results from the results
tables briefly in a non-interpretive way. Point out
the most important take-home points from the table
and/or any trends you would like to draw attention to.
- Go on to explain your interpretation of these
results. Your main aim is to show how they support the
theories presented in the background.
- 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). All peaks should always be labeled. By
labeling all solvent peaks and other expected
extraneous peaks (e.g., TMS, water, CHCl3)
you make clear what they are without unnecessarily
devoting lab report discussion to them.
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 2"x2"
zip-lock baggies.
- 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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