{"id":6198,"date":"2014-06-17T12:16:59","date_gmt":"2014-06-17T19:16:59","guid":{"rendered":"http:\/\/blogs.reed.edu\/chemistry201-202-test\/?page_id=6198"},"modified":"2023-08-01T16:30:43","modified_gmt":"2023-08-01T23:30:43","slug":"experimental-section","status":"publish","type":"page","link":"https:\/\/blogs.reed.edu\/chemistry201-202-lab-ref-manual\/appendices\/how-to-write-lab-reports\/experimental-section\/","title":{"rendered":"Formatting Your Experimental Section"},"content":{"rendered":"\n

The Experimental section is probably the most unusual (and most useful<\/em>) part of any research report. The language in the Experimental section is unusually terse, dense, and technical. At the same time, an Experimental section contains a large number of numerical parameters (including all characterization data<\/em> for every new compound) and there are strict conventions for reporting each number. The only way to be certain that you have observed these conventions is to consult the rules for each number as you type it in. (Please read that last sentence again. We are saying that you must consult a rule as you type each number. You cannot guess your way through this.) Because of these challenges, we have provided this special web page of instructions to help you through this critical section of your lab report.<\/p>\n\n\n\n

This page describes all of the formatting conventions that will apply to your Experimental section, but before getting buried in instructions, let’s take a look at a typical Experimental section. The following paragraph describes one<\/span> experiment (the synthesis of compound (7)<\/strong> from compound (6)<\/strong>) that was published in a recent research article (J. Zhou et al. J. Org. Chem.<\/em>, 2014<\/strong>, DOI: 10.1021\/jo501967m<\/strong><\/a>):<\/p>\n\n\n\n

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(\u2212)-tert-Butyl (3R,4R)-4-(6-Bromo-2-pyridyl)-3,4-dihydroxypiperidine-<\/strong>1-carboxylate (7).<\/strong> AD-Mix \u03b2 (33.5 g, 43.0 mmol) and methanesulfonamide (2.3 g, 23.9 mmol) were combined in a mixture of <\/em>tert-butyl alcohol (150 mL) and water (150 mL). The mixture was allowed to stir for 10 min at room temperature before being cooled to 0 \u00b0C. <\/em>tert-Butyl 4-(6-bromo-2-pyridyl)-3,6-dihydro-2H-pyridine-1-carboxylate (6)<\/strong> (8.10 g, 23.9 mmol) was added, and the reaction mixture was stirred at 0 \u00b0C for 5 h and 10 \u00b0C for 4 h and then warmed to room temperature overnight. Sodium sulfite (22 g) was added to the reaction and allowed to stir for 1 h. The reaction mixture was concentrated to half-volume under reduced pressure, and the remaining suspension was extracted with EtOAc (2\u00d7 75 mL). The organic layers were combined, washed with 1 M NaOH (1\u00d7 75 mL), dried over sodium sulfate, filtered, and concentrated under reduced pressure. The crude product was purified by silica gel column chromatography: 0\u221225% EtOAc\/hexane to afford (\u2212)-<\/em>tert-butyl (3<\/em>R,4<\/em>R)-4-(6-bromo-2-pyridyl)-3,4-dihydroxy-piperidine-1-carboxylate (7)<\/strong> (7.72 g, 87%) as a colorless amorphous solid: 1<\/sup>H NMR (400 MHz, CDCl3<\/sub>) \u03b4 7.62 (t, <\/em>J = 7.8 Hz, 1H), 7.45 (dd, <\/em>J = 10.1, 7.8 Hz, 2H), 4.22 (d, <\/em>J = 12.3 Hz, 1H), 4.15\u22123.85 (m, 2H), 3.12 (td, <\/em>J = 13.0, 2.6 Hz, 1H), 2.95 (t, <\/em>J = 11.7 Hz, 1H), 1.93\u22121.82 (m, 1H), 1.77 (dt, <\/em>J = 13.8, 2.5 Hz, 1H), 1.46 (s, 9H); 13<\/sup>C NMR (75 MHz, CDCl3<\/sub>) \u03b4 164.5, 154.6, 140.6, 139.6, 127.0, 118.8, 79.9, 74.4, 70.0, 45.7, 39.0, 37.3, 28.4; HRMS (ESI-TOF) m\/z [M + H]+<\/sup> calcd for C15<\/sub>H22<\/sub>BrN2<\/sub>O4<\/sub> 373.0763, found 373.0769; [\u03b1]D<\/sub> = \u22127.8 (c 0.78, EtOH).<\/em><\/p>\n<\/blockquote>\n\n\n\n

If you take the time to read through this paragraph carefully, you will discover that you can make fairly good sense out of the procedure, i.e., the first half. Then we get to the characterization data for compound (7)<\/strong> and everything seems to unravel. The characterization data begins at “1<\/sup>H NMR<\/em>” and is presented in four stages: 1<\/sup>H NMR data, 13<\/sup>C NMR data, high-resolution mass spectrometry or HRMS data, and finally, polarimetry or optical activity data. The authors do not report mp, bp, or IR data for compound (7)<\/strong>, but you will need to report these data whenever you have measured them. Unfortunately, HTML does not do complete justice to the special formatting (bold, italics, etc.) used in journal articles so you might also click this link<\/strong><\/a> to see a screenshot<\/em> image<\/em> of the experimental section in its original formatting.<\/p>\n\n\n\n

Before we actually dive into the formatting instructions, we should also mention this: the Experimental section recapitulates information found elsewhere in the article (maybe in the title? abstract? results?), but only<\/em> the Experimental provides 1) all<\/em> of the information needed to repeat the experiment as the authors performed it, and 2) all<\/em> of the characterization data needed to verify that the result of a repeat experiment is the same one observed by the authors. Therefore, there is a heavy ethical<\/em> burden on authors to get the Experimental section right. There are no shortcuts here.<\/p>\n\n\n

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General formatting<\/p>\n\t\t\t

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Each experiment is described by a single paragraph. The first item in the paragraph is the title<\/em> of the experiment in bold font. This is followed immediately (same paragraph) by a description of the experimental procedure, and then the characterization data. In general, the first characterization data reported are the mp or bp, followed by the product weight, and % theoretical yield. Spectroscopic characterization data come after that.<\/p>\n\n<\/div>\n\t\t<\/div>\n\n

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Reporting numerical data<\/p>\n\t\t\t

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The sample lab reports will help you master the language and formatting of experimental procedures. However, it is quite common for students to get confused about how to report quantitative<\/i> measurements inside the procedure. Here are some useful guidelines {tooltip}[NOTE]{end-texte}Additional tips specific to the reporting of spectroscopic parameters are listed in the next section{end-tooltip}:<\/p>\n\n\n\n