A. The Notebook: The laboratory notebook (bound composition book) may be purchased from the Eckerd College bookstore. The outside cover should be bear the name of the student, course number and name, day of the week you meet for lab and the instructor's name. Sequential page numbers should be placed in the upper outside corner of each page. The first page (numbered one and two) is left blank. The second page (numbered three and four) has the heading-Table of Contents-and lists each experiment (in numerical order) and the page number where the write-up begins.
B. General Requirements: The instructor grades, typically, only what is presented in the lab notebook. A scientist should never record relevant data on a scrap piece of paper. Always write everything in the lab notebook! Record all entries in ink. If a mistake is made it should be crossed out and the corrected information added. Do not erase anything! Hardcopy acquired during the lab or data analyzed using the computer may be taped to the left-hand page of the notebook. Neatness is required and is part of the grade.
When writing a lab report use the impersonal form. Some examples are
a) Incorrect: I added 12 grams of water to ...
b) Correct: Twelve grams of water were added to ...
Don't use commands.
a) Incorrect: Heat the mixture for ...
b) Correct: The mixture was heated for ...
C. Format of the Notebook:
Title: The title should be centered at the top of the first page at the beginning of the experimental write up. Under the title put your name first, followed by the name(s) of any partner(s) and the date. The following headings* should appear in the order shown following the Title, when discussing the laboratory experiment:
I. Purpose*: A clear, concise statement should be written which indicates what one is to accomplish in the lab. For example: The synthesis of cyclohene by the acid-catalyzed dehydration of cyclohexanol. Please notice that the purpose consists of two parts, it states what is to be accomplished, "The synthesis of cyclohexene," and it describes the method to be used, i.e., "by the acid-catalyzed dehydration of cyclohexanol." Be sure that your purpose includes these two parts: experimental goals and methods. The writing of the purpose requires an understanding of the basic objective of the experiment.
II. Theory: This section describes the chemical ideas and background behind the laboratory experiment and is a very important section of the write-up. For organic chemistry experiments it will contain chemical equations and occasionally mathematical formulas which demonstrate the principles of the experiment; itmay be a description of how an instrument works. Use analogies and drawings to help explain a concept. Don't crowd your drawings or equations in with your writing. For most labs this section will be at least one or two pages long while for others it may be longer. This section indicates your understanding of the science behind the experiment and is written in your own words.
III. Experiments/Reagents: Here one briefly describes the glassware and other experiment. A reasonably detailed sketch of the glassware set-up allows someone else to duplicate the experiment or synthesis you are carrying out. For synthesis experiments it is helpful to prepare a "Table of Reagents." This is set-up in the following manner:
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The first column, "Compound," lists the chemical compounds you are using in your experiment/synthesis. The second column, "MW," lists the molecular weight of the compound. If the material is a liquid and is going to be dispensed by a volume measurement, the density is included. It is important to know the origins of the compounds you are using, so the vendor name is provided. If the compound is synthesized, the page number where the synthesis occurred is provided. The fourth column records the amount of material actually dispensed, either by weight (grams) or by volume (mL). Note: this is the amount of material you actually use, not the amount called for in the experiment (of course, these should be close in value). The fifth column records the number of moles represented by the amount of material you dispensed (a calculation is generally required here). The last column records the molar ratio for the reagents involved in your reaction. Sometimes a 1:2 or 1:3 ratio is required; this must be taken into account in the amounts of material weighed out. In the present case there is a 1:1 molar ratio between the starting material and desired product. This allows one to calculate the theoretical yield for the synthesis, an important figure if one is to determine the % yield for the process.
In addition to the data in the table, it is useful to record melting points and boiling points of compounds if these might be of some help in executing the experiment. It is also helpful to draw the structures of the chemicals you are using along with their molecular formulas. In the end, all of this data is important if it should be necessary to repeat the experiment, either by you or someone else.
IV. Procedure (or Description of the method)*: The procedure, as actually carried out by the experimenter, should be recorded in sufficient detail to allow the experiment to be repeated by someone using only the student's laboratory notebook. Come to lab with a preliminary procedure outlined by numbered steps. As you actually carry out the reaction, write what you do in short but complete sentences. Do not copy the procedure from the laboratory manual, rather RECORD WHAT YOU DO AND WHAT YOU OBSERVE (color, turbidity, vapor generation, etc.). Use your own words.
V. Data: Place data tables and graphs in this section. Typically, in an organic synthesis experiment, one records melting points, boiling points, IR, 1H and 13C NMR and mass spectral data (we won't do mass spectrometry in our class). For example, let's say we synthesized ethyl propionate; we would record the spectral data in the following manner:
Ethyl Propionate (product #1)
bp: 99-101 °C
IR (NaCl plates, neat): 2985, 2910, 1740, 1465, 1372, 1192 cm-1.
1H NMR (CDCl3): 4.13 (q, J = 7.20 Hz, 2H), 2.32 (q, J = 7.56 Hz, 2H), 1.25 (t, J = 7.08 Hz, 3H), 1.14 (t, J = 7.56 Hz, 3H).
13C NMR (CDCl3): 174.40, 60.26, 27.71, 18.57, 14.32, 9.19.
This data is the data you will analyze in an attempt to determine the structure of the compounds involved in the reaction; thus, it is very important that you record these numbers accurately. Now, on a first reading of this page you won't know what the numbers associated with NMR mean, but you will learn this during the semester. The boiling point for this substance was determined during its distillation; the temperature represents the head temperature of the distillation apparatus.
The actual IR and NMR spectra and associated numerical printouts should be neatly taped in the notebook. If literature values are used in a calculation or comparison, be sure to report the source of the value to include title, author, edition and page number.
VI. Calculations: You do not need to include calculations associated with the stoichiometry of the reaction you are performing. You do need to calculate a percent yield, however. If you have trouble with this calculation, ask your TA or instructor for help, and do this duing the lab period. It is best to present you "yield," "theorectical yield," and "percent yield" together in table format.
VII. Results (or Conclusions): In determining what to include here refer back to the purpose. The material in this section answers the purpose. Were you successful in synthesizing the material you intended? How do you know this? what is the evidence? This is where your analysis of the spectral data becomes important. You need to go through and make sense of all this data; you need to relate it to the structure(s) of the compound(s) you synthesized; you need to make spectral assignments (more of this during the various labs). In the case of cyclohexene, you obtain a clear, colorless liquid: this is all you really know until you analyze your IR and NMR spectra. This is where you would say, "well, there is an absorption that corresponds to an O-H stretch in the IR spectrum of the product, and therefore it can be inferred that a hydroxyl group is present in the molecule." Be sure you are able to justify any statements you make regarding the success of your experiment; offer no unsupported opinions. Show chemical equations and discuss observations that support your claims. Any unusual observations or difficulties experienced might deserve comment here. Safety precautions required for the experiment should be noted here. If a comparison is made to a true value, then the percent error should be given. Something to bear in mind is that if a scientist decides to read your laboratory write-up, the person will first read the "Purpose" section and then turn to the "Results" section; hence, it is important that these sections be well written and complete.