Microsoft word - organic lab notebook guidelines.doc
Organic Chemistry Laboratory - Guidelines for Writing the Laboratory Notebook General Information: Each student is required to keep a bound (not spiral or loose-leaf) laboratory notebook that will be collected and graded at various times during the semester. For each experiment you should prepare a written report. These reports do not need to be lengthy. Your aim should be to write reports that are both concise and complete; do not “pad” your reports with unnecessary information. In addition to the following guidelines, be sure to read pp. 558-565 in your lab text (Pavia, Lampman, Kriz, and Engel, “Introduction to Organic Laboratory Techniques,” 4th ed.) and follow those suggestions as well. Before Lab: Advance preparation is very important in organic chemistry for the prevention of accidents and to promote understanding. Be aware of potential chemical hazards that you may encounter as outlined in the experiment and those noted by the instructor. “Cookbook” chemistry will not be tolerated. Sections 1-5 (and parts of 6) of the lab report are to be done before lab; failure to prepare the notebook can result in a “point” deduction for that experiment (25% for that lab). Students will not be allowed to work in the laboratory without a properly prepared notebook. Notebook Format: (Read pages 21 – 26 in your Pavia text) Leave a few blank pages at the beginning of the notebook for a Table of Contents and keep it up to date. Number the pages of your notebook in the upper right-hand corner of each page. Use an ink pen (not pencil) exclusively for writing in the notebook and record all observations and experimental data directly in your notebook as you are doing the experiment. If you make a mistake, draw a single line through the suspect entry, do not erase or obliterate the entry. Each report must contain the following 9 sections in the following order:
1. Experiment Number, Title of Experiment, Reference, Date, and Lab Partners Name. Ordinarily, the
reference will be your lab text. If the reference is a handout, attach the handout to your report.
2. Purpose. Provide a short statement of the purpose(s) of the experiment in your own words. Often the
3. Chemical Reaction(s). Use structural formulas to write balanced chemical equations for the main chemical
reaction(s). Do not write mechanisms here. Write the reaction conditions (solvent, temperature, catalysts, etc.) over the arrows. Then calculate the theoretical yield of the desired product in millimoles and milligrams (or grams). Clearly identify the limiting reagent.
CH3CH2CH2CH2OH + Br2 → CH3CH2CH2CH2Br + OH
Theoretical yield: In the example above, 7.65 mmoles of CH3CH2CH2CH2Br can be formed, so,
× (137.03mg/ 1mmol) = 1048 mg CH3CH2CH2CH2Br
Some experiments do not call for the preparation of a compound. In those cases, you can skip to the next section.
4. Table of Physical Constants: Make a table of physical constants for all the materials used and made in the
experiment. This is called a table of Physical Constants. See page 563 in Pavia for an example of this table. Prepare this table of literature values before class.
5. Separation Scheme: Separation (purification) schemes are discussed in pp. 560-561 of your lab text. Show,
by means of a flow chart, how the desired product is to be separated from the reaction mixture (i.e. solvents, excess starting materials, and unwanted side products). Be specific, but not overly detailed - see the examples in your Pavia text.Note: the separation scheme starts “after” the reaction has been completed. You can find a sample separation scheme on pg. 561 in your laboratory text.
6. Procedure: Write a concise version of the experimental procedure in your lab book. Do not copy verbatim from the text! Include sketches of any apparatus that is being used for the first time. Do not spend too much time here. During the experiment: write down any relevant observations that you make and any changes to the published material.
7. Data: Record all data directly in the notebook in tables or on labeled, underlined blanks that you prepared
Prepare a columnar Data Table of the major reactants and products. Leave blank space to record the actual yield (in grams or milligrams) and the percent yield of the desired product(s). CLEARLY show how you calculated the percent yield.
Neatly attach any graphs or spectra that you obtain to your notebook as part of this section.
8. Conclusions: Write a brief, coherent conclusion that focuses on the chemical and physical principles involved
in the experiment. Think of the purpose(s) of the experiment; was the experiment a success? Provide a brief explanation for any disagreement between your results and the accepted (i.e. literature) values. In some experiments, you may want to suggest ways the procedure could be improved.
This is the one area of the report that you should strive to write in complete, grammatically correct sentences. You should make a rough draft on scratch paper and then copy a revised version into your notebook. It is probably best to do the questions first, they will often give you ideas for the conclusion. Consult your lecture textbook or other references for additional information as needed. Example: Experiment 1: Isolation of the Active Ingredient of an Analgesic Drug
The following is an example of a poorly written conclusion. “Basically, you could say the experimet was a sucess. Our melting point was 115ºC. This wasn't real good but that wasn't my fault because we had to rush thru the experiment and couldn't find all our supplies at first. But I did learn lots of good lab techniques that we can use again.”
Worse than the obvious misspellings and rambling nature of the comments above, is the fact that nothing of substance was mentioned. For example, the experimental melting point was mentioned, but no comparison was made to accepted values - only a vague statement was made about the quality of the result (“This wasn't real good but.”).
The following is an example of a well-written conclusion. “In this experiment, acetylsalicylic acid, ASA (the active ingredient in aspirin), was extracted from a commercially prepared aspirin tablet. The percent recovery of acetylsalicylic acid from the aspirin tablet was low (42.6%). This low yield may be a result of a combination of factors: Decomposition of the product in methanol, transfer losses in the vacuum filtration step, and retention of some product on the alumina column. In addition, some of the acetylsalicylic acid may not have dissolved in the methanol used in the initial extraction. The melting point of the sample was found to be 123 – 127°C which is about 11 degrees lower than the accepted value of 135 - 137 °C stated in the laboratory textbook. This low value, coupled with the fact that the product melted over a relatively wide range of temperatures, suggests that the ASA was contaminated with impurities (e.g., salicylic acid or other decomposition products). The presence of dissolved impurities in a solid (solvent) lowers the melting point relative to that of the pure solid. This phenomenon is known as freezing point depression. To a first approximation, the extent to which the freezing point is lowered depends only on the number (concentration) of dissolved impurities (solute) and not their specific chemical References
1. Kotz, Treichel, and Weaver, Chapter 14 in Chemistry and Chemical Reactivity, 6th. ed., Brooks/Cole
Note that the second conclusion is not too long - only two paragraphs were written. The discussion in the first paragraph about the low percent recovery was prompted by answering question #1 at the end of the Exp. #1. In paragraph number two, the idea to discuss freezing point depression came from reading the background information about Exp. 1 in your lab book. Notice the use of a freshman chemistry text as an additional reference in the discussion of freezing point depression.
` In the conclusion, focus on interpretation and analysis of results. Do not just restate the procedure or
tell what you did during the lab experiment. While you may occasionally refer to some aspect of the procedure (especially when discussing the results) you should focus on analysis and interpretation of the results.
` If infrared, NMR, or mass spectra were obtained in the experiment, you should discuss in detail how
the spectra help confirm the identity of the sample that was analyzed.
` All spectra should be attached to the report with key peaks labeled on the spectrum and discussed in
the conclusion. If there are a number of prominent peaks in the spectrum, you should also summarize this information in the form of a table.
9. Questions: Answer the assigned questions (check the lab schedule for specific question numbers) at the end Grading:
Lab reports will be collected and graded at various times in the semester as decided by your instructor. The lab reports will be graded on either a “point” or a “percentage basis” (consult your instructor for details). Extensive corrections will not be made in each lab book. Mistakes and omissions will be marked in your lab book and a score will be assigned to your lab book as outlined below. Your laboratory grade will be determined largely from your laboratory notebook and your laboratory technique. You should strive to obtain good results in lab, but, in general, you will not be unduly penalized for low yields and poor results early in the semester. Report the results that you obtained, not the results that you thought you should have obtained. Keep in mind that a poorly organized, overly sloppy, or incomplete report will receive a lower grade than an “equivalent” notebook that is well organized, neat, and complete. The ability to write clear and effective technical reports is one of the most important goals of this laboratory class. Sloppy and incomplete work is not acceptable in an industrial, clinical, or business setting, and it is not acceptable here.
Each lab exercise and report will be evaluated in each of the following categories:
A sample laboratory report is available for you to examine in the J.C.C.C. Writing Center, EMC 308. You are encouraged to make use of the writing center. If the conclusion section of your lab report is poorly written, your instructor may re-quire that you go to the writing center and get help in making the necessary corrections. If you are sent to the writing center, you must get your lab book initialized by a writing center tutor. Repeating an Experiment:
Early in the semester, if you have an experiment that fails due to some blunder, you may be allowed to repeat the experiment (at the instructors discretion), with a point deduction to be determined on a lab-by-lab basis. A common pitfall early in the organic lab is “throwing out the wrong layer.” Do not carelessly discard a layer in an extraction process, test it to see if it is “organic” or “aqueous” before disposing of it. If you make some type of blunder that prevents you from completing an experiment, notify your instructor IN WRITING so that he/she may arrange for you to repeat the experiment. “Repeat experiments” are completely at the discretion of the instructor. If your instructor agrees to let you repeat an experiment it must be done in the next lab period while you are working on the next experiment. As the semester progresses, you will be expected to show improvement in your laboratory technique. However, by mid-semester, no experiments will be repeated. At that point, the instructor will provide you with some data from another group so that you can complete your report. The penalty for mid- to late-semester blunders is -20% for that lab.
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