Iodination of Salicylamide

docx

School

University of Massachusetts, Boston *

*We aren’t endorsed by this school

Course

256

Subject

Chemistry

Date

Feb 20, 2024

Type

docx

Pages

Uploaded by vazquezalexandra9

Iodination of Salicylamide Abstract: The purpose of the Iodination of Salicylamide experiment was to conduct an electrophilic aromatic substitution reaction of Iodine and Salicylamide in order to produce Iodosalicylamide. This experiment contained irrants in which eye protectant and gloves were necessary. The procedure involved combining the reagents sodium iodide and Salicylamide with a mixture of sodium thiosulfate and sodium hypochlorite in order to create the electrophilic substitution. This mixture was then filtered and recrystallized to contain the final dried product of Iodosalicylamide. Then, the focus would go on identifying the location of the Iodine in the product by observing the IR spectrum of the product and gathering information on its ring substitution pattern. The IR spectrum revealed a strong peak from 850-800cm which indicated

the reaction was a (1,2,4) tri-substituted product. The final product was weighed for its mass 0.115g and then the mass was used to calculate the percent yield and atom economy. Both yields were low were the percent yield was 22% while atom economy was 1.8%. Any sources of error in this experiment can be the filtering of the product and the recrystallization made afterward to remove the impurities. The experiment was successful because both targets, iodination of Salicylamide and determining the products ring substitution pattern was achieved. Chemical Reactions: Physical Properties: Compounds Meltin g Point Boilin g Point Density Compound Structure Molecular Weight Salicylamide 140- 144 o C 181 o C 1.33 g/cm 3 138.13g/mol

Sodium Iodide 661 o C 1,304 o C 1.5g/cm 3 149.89g/mol Sodium Hypochlorite 18 o C 101 o C 1.11g/cm 3 74.44g/mol Sodium thiosulfate 48.3 o C 100 o C 1.67g/cm 3 158.11 g/mol Iodosalicylamide N/A N/A N/A 263.03g/mol Introduction: need 2 references The experiment Iodination of Salicylamide involves an electrophilic aromatic substitution reaction were iodine is bonded into Salicylamide in either the ortho or para position in the molecule. This reaction of involving the electrophilic substitution is when the proton on the aromatic ring is replaced with the added iodine molecule. Because the benzene ring is stabilized, the iodide has to first react with pi bond of the benzene ring and break the aromaticity of the molecule. This in turn creates the cation and changes the stabilization of the benzene ring. To regain the aromatic of the molecule, the proton gets removed and added to create the double ring back and creating the stabilized molecule. This mechanism is the same for every benzene compound but where the iodine gets placed during the reaction can change the rate of the reaction and orientation of the reaction.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

To make the product, one important technique is used to gather the correct components form the reaction. Recrystallization took place in which it is “ a purifying technique where an impure solid compound is mixed with a solvent to saturated the product”(jOve). This in turn creates a more purified product as the finished product and it is important for this experiment because many impurities are expected due to it not containing green chemistry solutions. This final product was then weighed and used to determine the location of the iodine in the Salicylamide. In order to determine the location of the iodine bonded into the molecule, the use of an Infrared Spectroscopy is very important in this experiment because it can help for the determination of the functional groups in the product and give additional information on where the substituents are present. The visualization of strong peaks through the products IR lead to the indication of the products ring substitution pattern, therefore, the location of iodine can be determined. By observing the peaks in the IR around 700-900cm -1 , the position of the substitution patterns can be decided with the use of the table located in the manual. The location can also provide information on how the orientation of the reaction is, and the rate of the reactions “if reaction is slower, substituent deactivates ring and if reaction is faster, substituent activates ring.” (Schwartz). Procedure: (ref. manual, Part III) To conduct this experiment, it is important to have gloves and eye protectors because of the irritant solutions used for this lab. To begin, Salicylamide was measured to 0.250g and dissolved in a flask with 5ml of ethanol. Once dissolved, 0.3g of sodium iodide was added to the mixture and put in an ice bath with an attached air condenser to the solution. When temperature reached 0 o C, 9.2ml of sodium hypochlorite was added and mixed, this solution caused the mixture to change colors to dark-red in which once it went down to a pale yellow the solution was complete. This step takes around 10 minutes in which meantime, 2.5ml of sodium thiosulfate was gathered to get added to the mixture. Then, with the use of HCl, the solution was acidified until acidic. The procedure was complete and then filtering with the Hirsch tunnel was done to collect the precipitate of the mixture. This precipitate was then recrystallized with 95% ethanol and placed in an ice bath for 25 min to dry the product. This product was weighed and used to gather an IR spectrum of the iodination of Salicylamide. Data: Table 1: Number of measured compounds used and final mass results with percent yield Mass of Salicylamide 0.2696g Mass of Sodium Iodide 0.3664g Experimental mass of product 0.0115g Theoretical mass of product .513g Percent Yield 22% Atom economy 1.8% Calculations: .2696 g 138.13 g / mol = 0.0019 mol

0.0019 mol x 263.03 = .513 theoretical massof product % yieldof product = Experiment mass of product Theoretical Mass x 100 0.0115 g 0.513 g = 0.224 x 100% = 22% yieldof product massof atoms ∈ product massof reactantsused = % atomeconomy 0.0115 ( .02696 + 0.3664 ) = 1.8 % atomeconomy Analysis of Product: Figure 1: IR Spectrum of Salicylamide

Figure 2: IR Spectrum of Iodinated Salicylamide product A difference between Salicylamide and Iodinated Salicylamide was observed through the use of Infrared Spectroscopy. Figure 1 containing the Salicylamide IR presented the O-H peak of alcohol at 3177cm and a N-H peak (primary) at 3389cm. Also, it showed a strong peak at 750cm where it can be determined to be a (1,2) mono or di substituted ring pattern. Once the Salicylamide was iodinated the products IR presented a strong peak around the 850-800 range indicating the presence of a 1,2,4-trisubstituted ring. This means that the Iodinated product was achieved at a 1,2,4-trisubstituted pattern ring where the Iodine must be para to the O-H group in the molecule. The N-H group was seen much like the Salicylamide IR at a peak of 3454cm and a new peak formation at 2970-2880cm indicating a C-H stretch. Discussion: While conducting this experiment there are things to remember which take place. To begin with, the iodination of Salicylamide is one that involves irritants and are corrosive which means protective gear of eyes and careful procedure is necessary. The molecule of Salicylamide contains an O-H group, an NH2 group and a double bond O connected to a benzene molecule in Ortho positions. Therefore, when iodizing Salicylamide, it was expected that iodide would bond in an ortho position or para to the O-H group. In order to determine the position iodine took once the experiment was completed, an IR spectroscopy was done for the dried product and Salicylamide to compare. When comparing both results, the Salicylamide presented the O-H peak, a N-H peak and a strong peak located at 750cm. The peak located at 750cm is the one that indicated the ring substitution pattern of the molecule in which this one indicated a (1,2) di- substituted pattern. On the other hand, the IR spectrum for the Iodinated Salicylamide presented the same O-H and N-H peaks plus an additional C-H stretch peak around 2900. In terms of the substitution pattern for the ring, this product had a strong peak at 850-800cm indicating the iodination not only took place but that it bonded para position to the O-H group. The final decision on the location of the ring based of the products IR spectrum led to the conclusion of the molecule containing a (1,2,4) tri-substituted ring pattern. By knowing this substitution pattern, it

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

was also concluded that the iodine substitution on that para position activated the rate of reaction leading to a faster reaction because orientation of the substituent group. When calculating the percent yield, this experiment gave a low yield of 22% and an even lower atom economy of 1.8%. The low percent yield show that the experiment could’ve had errors made especially in the recrystallization phase. The atom economy of the product was associated with the amount of impurities that resulted from the procedure such as the excess NaCl by product that was filtered off the product and the non-green solutions used for the iodination of the Salicylamide. Any sources of error can be the recrystallization made of the product and the filtration of the mixture. Conclusion: The focus of this experiment was to iodinate Salicylamide by combining Salicylamide and sodium iodide, then determine the ring substitution pattern of the product through the use of the IR spectrum. This experiment contained materials that are irritants and corrosive so gloves and eye protectants were necessary. By looking at the IR spectrum of this product, a strong peak at the 850-800 lead to the conclusion that the product was a (1,2,4) tri-substituted ring pattern. This experiment was not green because materials used in this experiment and it also produced a big amount of impurities which cause the atom economy to yield low at a 1.8%. The percent yield was also low at 22% in which the mass of the product was weighed at .0115g. Overall, the experiment was successful because the focus was on gathering information for the determination of the ring substitution pattern which was concluded as a (1,2,4) tri-substituted molecule after the iodination of Salicylamide. Reference: 1. Katz/Schwartz pp. 135-138 Organic Chemistry , Laboratory Manual, Fourth Edition. 2. Jove. Purifying Compounds by Recrystallization. (n.d.). Retrieved October 30, 2020, from https://www.jove.com/v/10184/purifying-compounds-by-recrystallization Post Lab Question: 1. What are the possible iodination products? They can be 3-iodosalicylamide, 4-iodosalicylamide and 5-iodosalicylamide. 2. Predict the most likely site of iodination and explain? 3-iodosalicylamide is not possible because of steric hindrance and the size of the substitution groups. Therefore, only 4-iodosalicylamide and 5-iodosalicylamide. The most likely would be 4-iodosalicylamide because it would be para position to the O-H group which is already a ortho-para directing group. 3. What product was actually produced? How do you know this? The product was 4-iodosalicylamide produced and it was determined with the use of the IR spectrum collected from the product where it showed a strong peak band in 814cm indicating the ring substitution pattern of (1,2,4) tri-substituted molecule which is the same as the iodine being para to the O-H directing group.