First and foremost, Formal Written Lab Reports are independent works by each individual in a lab group. The planning, the writing, and everything related to the written report is each individual student's work. While you did the experiment together and collected data together, every aspect of the writing of your formal report is done by only one student, YOU.

Lab reports require the turning in of your lab notebook, or copies, for each and every experiment performed during the semester. There is no exception to turning in a completed laboratory notebook for each experiment, regardless whether a formal written lab report is turned in. These two types of reports are separate, and graded separated (do not staple one to the other).

It is important to turn in your formal written lab reports in order to get the maximum number of points possible. Formal written reports will be worth a maximum of 30 points. For the most part, grading of the formal report usually starts out with a grade of 25 points out of 30 maximum points or an 83% score (which amounts to about a "B-" grade which is the typical average grade for the class). If you do better than expected of a good report, you will have points added to give a higher score. Rarely will anyone receive a perfect 30 points on a formal written report. If you do less than expected, points will be deducted from the 25 point starting score. If formal written reports are turned in after the day they were due (at the same time your lab notebook was due) up to one week after the report was due, according to the syllabus, you will be subject to a 10% reduction in your grade (you will lose 3 points automaticlly). If your formal written report is turned in after that first week but before the ending of the second week after it was due, you will lose another 3 points (for a total 20% deduction). If your formal report is turned in after that two week late period, you will lose an additional 3 points or a total of 9 points (30% deduction). It is important to turn your reports in on time. I do not accept E-mailed reports under any condition.

When a formal written lab report is required, the format changes for this report, as it is not just the content of the laboratory notebook. The format and content of the formal report is described here. There are only a few formal reports turned in during the semester, and the experiments that can be used for a formal written report are listed in the syllabus. A formal lab report must be typewritten and will be graded according to how well it is written as well as on the content.  The table below lists most of the information that is needed for a formal written report.  A sample report is shown as well, but may not be completely accurate for content, so check with your instructor.  Use this information as a guide.

Your lab report should follow the pattern described below. The report does not need to be long, but it needs to cover the experiment, including protocols, observations, results and disccusion, and the conclusion sections.  Do not use an outline format as everything must be in full sentences and proper grammar and correct verb tense throughout.  You do not include every detail of the experiment, because certain techniques, such as Separatory Funnel extractions, melt point determinations, and refluxing because these techniques are known to everyone (do not include items like boiling stones, etc.).  Use correct English, in complete sentences.  Your experiment data is always described using past tense (e.g., The refractive index of our product was 1.3456; Our DNA sequence was 5'-AGCTTGT-3', etc.).  Established data is described in the present tense (e.g., The refractive index of this chemical is 1.3456; The DNA sequence is 5'-AGCTTGT-3', etc.).

Sample Report:

Electrophilic Aromatic Substitutions: Nitration and Friedel-Crafts Acylation

Someone Great

ABSTRACT

Electron electron deficient reagents (commonly referred to as electrophiles) react with the electron rich aromatic rings. This type of reaction is known as an Electrophilic Aromatic Substitution (EAS). While electrophilic aromatic substitution involves a wide variety of reactions they all follow a similar reaction mechanism usually in strong acidic conditions.  Nitration and acylation reactions described here use acid-catalyzed nitration and acylation using Friedel-Crafts reactions. These experiments examine the behavior of the aromatic ring, when exposed to electrophilic reagents, and the preferred orientation of the resultant product based on which attached substituent groups are already present. Overall, these reactions demonstrate one of the most practical organic chemistry synthesis techniques.

INTRODUCTION

The characteristic reactions of aromatic compounds like benzene and related compounds involve substitution. The benzene ring has a cloud of electrons above and below its plane which are loosely held and are available to an electrophilic reagent that is seeking electrons. Since the benzene ring serves as a source of electrons -- it acts as a Lewis base (an electron pair donor). The electrophilic reagent which reacts with the benzene ring is electron deficient -- it acts as a Lewis acid (electron pair acceptor). The reaction of the aromatic ring and the electrophile is characterized specifically as an Electrophilic Aromatic Substitution (EAS) reaction.

The mechanism for electrophilic aromatic substitution for both nitration and Friedel-Crafts acylation involves two essential steps. The first is the attack on the ring by an electrophilic reagent to form a carbocation on the ring structure (this is characterized as the rate determining or the slow step). It must be noted that the attack generates a carbocation not because of a positive charge on the electrophile, but because a pair of electrons are pulled out of the ring to form a bond with the electrophile leaving a carbon in the ring electron deficient. The second step is the abstraction of a proton from the carbocation on the ring by some base (characterized as the fast step). Each of the EAS experiments follow these principles and reaction mechanism which offer powerful techniques for organic chemistry synthesis.

MATERIALS AND METHODS

Nitration of Methylbenzoate. In a 125-mL Erlenmeyer flask, 6.1 g of methyl benzoate were combined with 12 mL concentrated (18 M) sulfuric acid. The reaction mixture was cooled to 0^oC prior to the addition of 8 mL of a nitronium ion producing a mixture composed of equal volumes of concentrated sulfuric and nitric acids (these acids are mixture thorough prior to addition to the reaction flask). After the addition of the two acids, the reaction flask was slowly warmed to room temperature and then allowed to react for about 15 minutes.

After the 15-min incubation, the reaction was stopped by pouring the room temperature reaction mixture over 50 g of crushed ice. The ice was used to keep the reaction mixture cool and to facilitate precipitation of product. Solid product crystals were isolated using vacuum filtration with a Büchner funnel. The collected crystals were washed twice with 25 mL cold water followed by two washes with 10 mL ice cold methanol. The collected crystals were dried and then weighed for yield and percent yield calculations.

Synthesis of p-Nitroaniline. Three grams of acetanilide were mixed with 5 mL of concentrated sulfuric acid in a 125-mL Erlenmeyer flask. The acetanilide was dissolved by gentle swirling or by stirring. After the acetanilide was dissolved, the flask was cooled in an ice bath. To this flask was added a reaction mixture composed of 1.8 mL of concentrated nitric acid and 5 mL of concentrated sulfuric acid was added drop-wise using a disposable pipette. After every 5-8 drops, the reaction mixture was cooled by swirling in the ice bath.

After 20 minutes, including the time required for adding the nitric acid-sulfuric acid mixture, 25 mL of ice water were added. A suspension of p-nitroacetanilide isomers resulted. To hydrolyze the p-nitroacetanilides to their corresponding p-nitroanilines, the mixture was heated. The dilute sulfuric acid already present in the flask served as the hydrolyzing medium. Heating the mixture allowed the solids to dissolve. The flask was cooled in an ice bath and 30 mL of concentrated aqueous ammonium hydroxide was added. The p-nitroaniline isomers precipitated during this step. The precipitated p-nitroaniline was collected using a Büchner funnel. The solid was washed with small amounts of water (total about 50 mL). The sample was then air dried.  A product yield and percent yield calculations were performed on the dry material.

In order to effect a purification of the product, the dry material was added to hot ethanol and dissolved. After the first crystals appeared in the boiling mixture, the flask was allowed to cool to room temperature, and then placed in an ice bath to complete the crystallization. Crystals of p-nitroaniline were collect by vacuum filtration. The crystals were washed with a minimum amount of cold ethanol and allowed to dry. The re-crystallized p-nitroaniline was dissolved in 15 mL ethanol for each gram of p-nitroaniline and the solution warmed to dissolve the solid. About 0.5g of activated charcoal was added to the solution and swirled for a few minutes. The charcoal was removed by gravity filtration. The filtrate was concentrated to about 1/3 of its original volume by heating on a hot plate. When the solution cooled, and the first crystals appeared, the flask was placed in an ice bath. After the crystals were collected, they were dried in air and weighed.

A Friedel-Crafts Acylation: About 2.8 g of anhydrous aluminum chloride were added to 5 mL of methylene chloride in a 100-mL round bottom flask and mixed by stirring using a stirring bar. 1.6 g of acetyl chloride mixed with 4 mL of dichloromethane was added to the reaction flask over a 15 minute period. After addition of the above reagents was complete, 1.4 g of toluene which had been dissolved in 3 mL of dichloromethane were added to the reaction flask over a over 20 min period. After all of the reagents had been mixed, the reaction was allowed to proceed for 30 minutes stirring constantly.

The completed reaction mixture was poured into a mixture of 10 g of ice and 5 mL of concentrated hydrochloric acid (12 M). This solution was mixed thoroughly for 10-15 minutes. The entire reaction mixture was added to a Separatory funnel.  The upper organic layer was collected and saved. The aqueous layer was extracted with 6 mL of dichloromethane to reclaim any reaction product found in the aqueous mixture. The two organic layers were then combined and washed with 10 mL of saturated sodium bicarbonate solution and then dried with anhydrous sodium sulfate.

RESULTS AND DISCUSSION

For the first reaction, the nitration of methyl benzoate, a yield of 7.832 g was achieved and based on melt point analysis, the chemical was likely to be m-nitrobenzoate. Although an ester is a deactivating compound, the reaction appeared to proceed reasonably well, with a good overall yield. The major product was likely to be the meta-isomer because deactivating groups (since they withdraw electrons from the ring, making it more positive and less attracted to a positively charged electrophile) is generally considered to be meta-directing. In addition, a mono-substituted product would be likely for two reasons. First, the experiment was conducted using relatively low temperatures meaning that reaction would not occur rapidly. Second, the newly added nitro group, when attached to the ring, would lead to additional deactivate. Overall, this would tend to prevent, or at least slow down further substitution. After collection by vacuum filtration of the product, the meta-isomer would be in a very high proportion, if any ortho- or para-isomer were present.

This particular experiment initially brought about some confusion. At first, I wondered why I couldn't directly nitrate aniline to make p-nitroaniline (it is strongly activating, the para product would seem likely). However the text revealed that since this electrophilic aromatic substitution reaction occurs in acidic media, the basic amino group is converted into the cationic ammonium group (-NH₃⁺) which is electron withdrawing and would be meta not para directing. This is why it was necessary to convert the amino group into the acetamido group which would reduce the reactivity of the amino groups reactivity with acids. I obtained a yield of 0.74g of p-Nitroaniline. Since I knew that acetamido group (-NHCOCH₃) is strongly activating, I expect that I obtained predominately the para product with some ortho isomer. But why mostly para? According to the text, "steric hindrance makes ortho substitution much less likely than para substitution" (Pavia, 237).

Toluene was used as substrate using the acylating agent acetyl chloride. According to the text, I expected to have a single product, a substituted acetophenone. However, according to lecture, Friedel-Crafts reactions have limitations that must be noted. Namely, these reactions are succeptible to rearrangements and polysubstitution. My refractometer reading was 1.5290 which, according to Dr. Robertson, was well within the range of acceptable values (this value reassured me that my product was the desired product and not a rearranged or polysubstituted product). According to the Acros Organics catalog, the melting point and boiling point for 4-methylacetophenone (95%) are 22-24^oC and 226^oC , respectively. The known refractive index value is about 1.5330.

LITERATURE CITED

1. Introduction to Organic Laboratory Techniques, 3rd ed., pgs. 232-247, Pavia, Lampman, Kriz.

2. Acros Organics 95 & 96 Catalog of Fine Chemicals, Fisher Scientific.