Nucleophilic Substitution Reaction Lab Report

Conducting Results from Various Substitution Reactions that Contain Alcohol Sophia Gruszczyk*, Riley Clark Department of Chemistry and Chemical Biology, IUPUI, 402 N. Blackford St., Indianapolis, IN 46202.

[e-mail]

The purpose of this experiment was to determine the structure of a specific product(s) from a given starting material. The reaction that was tested was that of substitution reactions, whether it was SN1 or SN2. Reaction 1 is an SN2 reaction because of the presence of a strong nucleophile and the solvent being polar aprotic. For this reaction, there is only going to be one product which is (3-bromopropyl) benzene. Reaction 3 favors SN1. Since the solvent is polar protic, there is a weak nucleophile, and there is a secondary

One of the ways they can do this is through substitution reactions. There are two different types of substitution reactions, SN1 and SN2. Substitution reactions are when one atom or ion is substituted for another. An SN1 reaction is a unimolecular, nucleophilic substitution that is 1st order. However, an SN2 reaction is a bimolecular, nucleophilic substitution that is 2nd order. Both reactions have key components that make each easily identifiable. These things to look out for are the nucleophile, which is a Lewis base that donates electrons, and the electrophile, which is a Lewis acid that accepts electrons and carries the leaving group. Alcohols react with substances like HCl and HBr during substitution reactions because alcohol is not a good leaving group. Determining if the reaction will be SN1 or SN2 is based on the structure of the alcohol and which way the carbocation forms. The solvent also plays a role in what the product will form. If there is a polar aprotic solvent, the reaction will be SN1 and will produce a different product than if a polar aprotic solvent was used, which will be an SN2 reaction. All these components will in turn affect what the final product or products are, and examining the products will aid in confirming if the reaction aligns with being SN1 or SN2. Using the information gathered allows scientists to better identify

The OH group is not a good leaving group, so it needs to be protonated with the H2SO4. This will allow water to become the leaving group. When the water leaves, a primary carbocation is produced and only SN2 reactions occur with a primary carbocation and a polar aprotic solvent. The bromine will come and attack the negative charge, the loss of the leaving group leaves on the carbon, forming the desired product. Aromatic rings have a high boiling point, so it was important when running this experiment to carefully watch the reaction so that the solution was not going to burn. This would have resulted in the loss of essential products. Since there is a high activation energy for this reaction, it is necessary to heat using reflux. Heating with reflux also makes it important to be wary of not burning/losing any of the product. The IR appears to be correct as there is no OH peak around 3500 cm-1. TLC was also run for this experiment and showed that the alcohol did not travel, however, the final product did. This indicates that there was a change. When running the GC, there are no peaks for a product, only the acetone. The 1H NMR appears to be correct based on the data.

Synthesis of Scheme 2, which has a secondary alcohol, yielding the products and byproducts presented after reflux with hydrochloric acid and zinc