Docx-8 - lab 8 lab report of 238 PDF

Preview

Summary

lab 8 lab report of 238...

Description

Colton Aleman CHEM 238-516 TA: Jialuo Li

Iodination of Salicylamide Abstract In the Iodination of Salicylamide, sodium iodide was added in solution to salicylamide to produce a 1,4 – disubstituted product containing amine and iodo substituents. The melting point range was narrowed to 244°C - 246°C. This reaction demonstrated the properties of electrophilic aromatic substitution reaction, wherein the iodide acted as the electrophile attaching to the aromatic salicylamide. Introduction In the Iodination of Salicylamide, the objective to obtain was to successfully perform an electrophilic aromatic substitution. Electrophilic aromatic substitution is one of the most important reactions possible on an aromatic ring, and one of the most common. The basic mechanism of the reaction begins with an electrophile attaching to the aromatic ring by reacting with and electron pair, causing the formation of a carbocation. After this, the free proton leaves the carbocation, allowing the electrons to re-enter the compound, reforming the aromatic ring and completing the electrophilic aromatic substitution. In Experiment 5, the electrophilic aromatic substitution reaction involved the substitution of Iodine to Salicylamide. Methods In Experiment 5, two test tubes were acquired, one containing 20 mL of absolute ethanol, and one containing 7.0 mL of NaOCl (bleach). 0.9964 g of solid salicylamide was added to a flask and dissolved with the ethanol. After this, 1.2065 g of solid sodium iodide was added to the solution, then stirred at 150 rpm. Once the solution reached homogeneity, it was placed in an ice bath and cooled to 0.0°C. 7.0 mL of NaOCl was then added quickly to the solution and stirred vigorously. As the reaction commenced, the solution took on different colors, first as a dark, almost brown orange, the reddish orange, then a golden color, then a strong yellow, before finally settling on the desired pale-yellow color. At this point, the solution was allowed to settle undisturbed for 10 minutes. At the end of the 10 minutes, 10 mL of sodium thiosulfate was added to the reaction and thoroughly mixed in. Then the solution was slowly acidified to a pH of 2 with approximately ~8.0 mL of HCl. A crude product was then recovered from the solution by vacuum filtration. This product was then washed four times with 10 mL of cold water, followed by one portion of 10 mL of ethanol. This product was then dissolved in 10 mL of boiling ethanol. Once totally dissolved, the solution slowly cooled to room temperature, then cooled in an ice water bath to catalyze recrystallization. This crystallized product was retrieved by vacuum filtration and allowed to dry for one week. After the one week wait period, the final mass was recorded as 0.3581 g. Two melting point ranges were determined. The first range was a fast range, found to be 240°C - 247°C. This was then followed by a slower melting point range in order to narrow down the range to an actual melting point. The slower melting point range was found to be 244°C - 246°C. An IR spectrum was determined using the product as well. Results and Discussions

Colton Aleman CHEM 238-516 TA: Jialuo Li

In determining the structure of the derived product, the IR spectrum holds much information. A peak at 3439.04 shows the presence of N-H stretch bonds, indicating a 1° amine. The peak at 3193.91 displays C-H stretch bonds in the aromatic range, proving that the product is an aromatic ring. This is also proven by the presence of overtones within the IR spectrum. In the fingerprint region, the two peaks at 839.77 and 816.90 indicate that the product is 1,4 – disubstituted. The range a 1,4 - disubstituted product is 870 – 800. This accounts for the 1° amine substituent and the iodo substituent. While it could also fall into the 1,2,4 – trisubstituted range, which is 850 – 800, the third substituent would have to have been a hydroxy substituent. However, in the IR Spectrum, there was no peak that corresponded to an O-H stretch bond. This leads to the inference that the product is disubstituted. This is also supported by the fact that -NH2 substituents are ortho/para directing, which would account for the product being 1,4 – disubstituted. A possible error in this experiment is the use of HCl to acidify the solution. Making the solution too acidic would have altered the amount of product in the solution. Since the amount of HCl added to the solution was not specified, only an approximate, the amount of HCl would have varied from table to table. Another source of error would have been adding of too much ethanol to the recrystallizing product. This would have caused too much of it to dissolve, leading to a loss in product. Conclusions In conclusion, the iodination of salicylamide led to a 1,4 – disubstituted product containing an amine and an iodo substituent, respectively. This was due to the ortho/para directing effects of the amine substituent. This reaction was an example of the common reaction associated with aromatic rings, electrophilic aromatic substitution....