Nucleophilic Substitution Reaction Lab Report

Experiment 55 consists of devising a separation and purification scheme for a three component mixture. The overall objective is to isolate in pure form two of the three compounds. This was done using extraction, solubility, crystallization and vacuum filtration. The experiment was carried out two times, both of which were successful.

The objective of this laboratory experiment is to study both SN1 and SN2 reactions. The first part of the lab focuses on synthesizing 1-bromobutane from 1-butanol by using an SN2 mechanism. The obtained product will then be analyzed using infrared spectroscopy and refractive index. The second part of the lab concentrates on how different factors influence the rate of SN1 reactions. The factors that will be examined are the leaving group, Br – versus Cl-; the structure of the alkyl group, 3◦ versus 2◦; and the polarity of the solvent, 40 percent 2-propanol versus 60 percent 2-propanol.

After 10 minutes the reaction liquid was separated from the solid using a vacuum filtration system and toluene. The product was stored and dried until week 2 of the experiment. The product was weighed to be 0.31 g. Percent yield was calculated to be 38.75%. IR spectra data was conducted for the two starting materials and of the product. Melting point determination was performed on the product and proton NMR spectrum was given. The IR spectrum revealed peaks at 1720 cm-1, which indicated the presence of a lactone group, and 1730 cm-1, representing a functional group of a carboxylic acid (C=O), and 3300cm-1, indicating the presence of an alcohol group (O-H). All three peaks correspond with the desired product. A second TLC using the same mobile and stationary phase as the first was performed and revealed Rf Values of 0.17 and 0.43for the product. The first value was unique to the product indicating that the Diels-Alder reaction was successful. The other Rf value of 0.43 matched that of maleic anhydride indicating some

The solution was let cool in ice water then using vacuum filtration to obtain the final product. Although the obtained product was white like powder, the identity of the product couldn’t be confirmed as cyclododecanone yet. Letting the obtained product stay open on the watch glass overnight to make sure all methanol evaporated. Following the third part was infrared spectroscopy and melting point to characterize the

When mixed phenylboronic acid and p-iodophenol, a yellow solution was observed. The added Pd/C suspension stayed at the bottom of the flask. When cooled the flask containing reaction mixture to room temperature after 30 minutes reflux, white thin layer was formed upon the mixture. Filtered the reaction mixture by suction, a white/greyish solid was collected in the filter paper. Recrystallized this solid, white solids were obtained with a close melting point to that of final product. The NMR spectrum of this solid also showed the aromatic peaks. This solid was suggested as an intermediate of reaction, mostly likely ArOH-Pd-Ar in reductive elimination. Since a ligandless palladium catalyst was used in this reaction, a transformation from trans complex to required cis complecx was unnecessary. The unreacted intermediate may be left on the filter paper. This complex contained two phenyl groups which gave the aromatic peak in NMR spectrum. Because of the presence of the

2. Plan: Each student in a group of three will work to create a reaction with the Benzonitrile Oxide with, cis-stilbene, trans-stilbene, or styrene in an Erlenmyer flask. With this Reaction solution thin layer chromatography will be performed using each reaction solution. The different reactions will then be compared by running co-spot TLC’s. An NMR of the crude products from each reaction will be taken.

The purpose of this experiment was to perform a nucleophilic substitution reaction to construct a biologically active compound from two simple parts and then to recrystallize the product collected, which is a purification technique that purifies solids based on differences in solubility. In order to accomplish this, other techniques such as heating at reflux, and suction filtration were used. Heating at reflux is a technique used in lab that allows a solution to be heated for a certain amount of time once it begins boiling. Suction filtration is a separation technique that is combined with a water aspirator and was used to collect the product from this experiment, which was 2-methylphenooxyacetic acid.

The solvolysis of t-butyl bromide is an SN1 reaction, or a first order nucleophilic substitution reaction. An SN1 reaction involves a nucleophilic attack on an electrophilic substrate. The reaction is SN1 because there is steric obstruction on the electrophile, bromine is a good leaving group due to its large size and low electronegativity, a stable tertiary carbocation is formed, and a weak nucleophile is formed. Since a strong acid, HBr, is formed as a byproduct of this reaction, SN1 dominates over E1. The first step in an SN1 reaction is the formation of a highly reactive carbocation, in which a leaving group is ejected. The ionization to form a carbocation is the rate limiting step of an SN1 reaction, as it is highly endothermic and has a large activation energy. The subsequent nucleophilic attack by solvent and deprotonation is fast and does not contribute to the rate law for the reaction. The Hammond Postulate predicts that the transition state for any process is most similar to the higher energy species, and is more affected by changes to the free energy of the higher energy species. Thus, the reaction rate for the solvolysis of t-butyl bromide is unimolecular and entirely dependent on the initial concentration of t-butyl bromide.

Table 1: Properties of the reagents and possible products for the reaction. The boiling point of Phosphoric acid is not important because it is a reagent.

In a bimolecular nucleophilic substitution or SN2 reaction, there is only one-step. This occurs because the addition of the nucleophile and the elimination of the leaving group spontaneously occur at the same time.

After allowing the flask to cool to room temperature and cooling on ice, the product was collected and washed with 2-propanol (2ml) into a clean Hirsch funnel and was filtered using vacuum filtration. The triphenylphosphine oxide remained in the propanol solution, and the crystals were dried by drawing air through them. The mass, percentage yield and melting point of the product was obtained. The crystals were stored in a glass vial for next experiment.

After drying out the product and recrystallizing it for weighing, it was determined that the total weight of the product was 0.091g which gave a percent yield of 32.535%, meaning that the overall the reaction was successful however there are quite a few areas for improvement in this experiment to increase the yield of the reaction. The melting point of the product was taken to be 170.7 degrees C meaning that the product produced, despite having a low yield, was in fact acetaminophen and not p-aminophenol which would have melted at a higher temperature of 188-190 degrees C. Looking at the TLC plate it was shown that the reaction did in fact reach completion because the final reaction mixture eluted as far as the acetaminophen standard and not as far as the p-aminophenol standard, meaning that the acetaminophen standard and the reaction mixture had the same contents, without and p-aminophenol. Finally looking at the IR spectrum, there is a peak at around 3320 cm-1 which signifies a N-H amide stretch, there is a broad peak at about 3107 cm-1 which is the phenolic OH stretch, and is broadened by the strong hydrogen bonding.

The objective of this experiment was to illustrate electrophilic aromatic substitution by synthesizing p-nitroanilide (as well as ortho) from acetanilide by nitration. The para form was separated from the ortho form based on solubility properties using recrystallization techniques.

The raw atenolol and metoprolol powder were the kind gift from Swiss Pharmaceutical Co., Ltd, Taiwan. Chemically, atenolol (free base) and metoprolol have a molecular weight of 266 and 267 (Lennernasi, et al., 1994; Gros, et al., 2006b), the melting point between 152℃ and 156.5℃ (USP, 2005). It is a relatively polar hydrophilic compound with a water solubility of 13.3 mg/mL at 25℃(Gros, et al., 2006b). The extent of ATN molecule was estimated to be 7x18.2 Å (Lennernasi, et al., 1994, Sybyl®; Fagerholm, et al., 1999). The pka of ATN and MTN were 9.6 and 9.7(24℃) (Lennernasi, et al., 1994). Since the compound was in protonated form at pH < pka, which the solution was basic, the neutral ATN and MTN molecules are the dominant specie (Pasti et al., 2013). The surface areas were 34.1±2 Å2 (Seelig, et al., 1994). The dynamic volume were 343 and 364 Å3 for ATN and MTN, respectively (Palm, et al., 1997). An awesome feature of beta blockers is that they have been reported to behave as weak cationic surfactants at neutral pH (Mosquera et al., 1999).

Objective: The purpose of the lab was to see if when two compounds were combined a reaction would occur. If the reaction did occur we wrote a balanced chemical equation of the products and reactants with the correct solubility rule.