Synthesis Of 4-Nitrobromobenzene Lab Report

1570 Words 7 Pages
Abstract
This experiment involved an electrophilic aromatic substitution of bromobenzene. Two products were formed: 4-nitrobromobenzene (4-NBB) and 2-nitrobromobenzene (2-NBB). Utilizing column chromatography and recrystallization, separation and purification of the two products was obtained. The mass of 4-NBB, the para product, was 1.57 grams, while the mass of 2-NBB, the ortho product, was 0.80 grams. The para product was expected to have the higher yield, since it is more stable and consequently harder to break down throughout the experiment.

Keywords
Nitration, Bromobenzene, Substitution, 4-nitrobromobenzene, 2-nitrobromobenzene, Column Chromatography, Infrared spectrum, Thin-Layer Chromatography.

Introduction
This experiment
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The expected yield for 4-NBB is 46% [8]. It was expected to gather a greater percent yield from the 4-NBB due to the stability of the compound. The stability results in less of the compound to be broken down throughout the experiment, resulting in a higher percentage. 2-NBB is less stable than 4-NBB, causing a lower percent yield.
IR spectroscopy aids in determining the composition of a compound, allowing for identification. 2-Nitrobromobenzene was shown in product 1, but 4-Nitrobromobenzene could not be tested due to the small amount of product obtained. The two compounds can be distinguished by the peaks on the IR spectroscopy. 4-NBB contains an arene group, while 2-NBB contains an aldehyde/ketone group. The Thin layer chromatography plate shown in Figure 3 is used to identify compounds as well as determine their purity [9]. The crude product spot moved the same distance as the 2-NBB spot. The 4-NBB spot did not appear on the plate, indicating a low concentration of the substance. 4-NBB should diffuse farther up the TLC plate than 2-NBB due to the difference in polarity.
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A mixture of 5.0 mL concentrated nitric acid and 5.0 mL concentrated sulfuric acid was prepared in a 100-mL Erlenmeyer flask and was placed into a water bath to cool to room temperature. 3.93 grams of bromobenzene was added to the solution over a period of 10 minutes with constant mixing. After all of the bromobenzene is added, the mixture was heated with a hot water bath for 30 minutes. The flask was cooled to room temperature and then poured into 50 mL of ice-cold water in a 200 mL beaker. The crude product was isolated by vacuum filtration and then washed with cold water. The crude product was then allowed to drain under vacuum until nearly dry. The aqueous filtrate was disposed of in the sink with running

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