Bromination Of Trans-Stilbene Lab Report

To start off, in an Erlenmeyer flask approximately 0.51 g of E-stilbene with 10 mL of acetic acid was dissolved. A hot water bath was prepared and the mixture was warmed until the solid is completely dissolved. After the solution was dissolved, 1.02 gram of pyridinium hydromide perbromide was added. The crystals around the flask were rinsed with a small amount of acetic acid and the solution was continued in the hot water bath for one to two minutes.

Also I have recollected how to use molecular model, which helped me to simulate both syn and anti addition of bromine to trans-cinnamic acid. This review helped to figure out whether the product was formed by syn addition, anti addition or both.

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.

Two forms of stereochemistry can form product for the bromination of trans-cinnamic acid. Cis addition, also known as syn addition, is one way of forming product. This form of stereochemistry allows for the components of the reagent to add to the same side of the double bond. Trans, also known as anti addition, is the second form of addition that can create product for this experiment. Tran stereochemistry occurs when the components of the reagent add to opposite sides of the double bond. In this experiment, the formation of either erythro-2,3-dibromo-3-phenylpropanoic acid (trans/anti-R,S or S,R) or threo-2,3-dibromo-3-phenylpropanoic acid (cis/syn-R,R or S,S) was expected to occur.

As detailed in Pavia 's Organic Laboratory techniques the reaction is expected to proceed via the following reaction:

Olmsted, John III; Williams, Greg; Burk, Robert C. Chemistry, 1st Canadian ed.; John Wiley and Sons Ltd: Mississauga, Canada, 2010, pp 399 - 406

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.

The SN1 mechanism leads to substitution products, and the E1 mechanism leads to formation of alkenes, therefore in this case, it is shown that this mechanism leads to a substitution of products since the Cl- ion is replacing the OH group by the addition of a strong acid (HCl). When the nucleophile

The reaction was determined to be SN2 after careful reading of the data obtained and the procedure followed. Increasing the amount of NaBr used in the reaction did not have an effect on the product yield. The conditions of the reactions were acidic due to the solvent used. The acidic conditions prevent an E2 substitution reaction from occurring. In this reaction, the OH leaving group is replaced with the nucleophile Br. The bromine attacks the first carbon and the OH group leaves in the same step. This is a concerted process or bimolecular substitution mechanism (SN2). The location of the leaving group (primary) also indicates the reaction is SN2. The data obtained from 1H NMR was found to confirm the correct product was formed. The data showed the correct location and coupling of hydrogens in the product. There should be a difference of polarities between the starting material and the product. The product should travel further on the TLC plate than the starting material because the starting material should be more polar than the product. The TLC results confirm the product was less polar than the

The triple bonds of the alkynes are subject to electrophilic additions reactions. Electrophilic reagents, or Lewis acids, can easily react with the pi-electrons of the triple bond, which act as a Lewis base. An equivalent amount of a halogen or hydrogen halide can be added to produce a double bond and a second equivalent amount can be added to create a saturated product.

The purposes of this experiment were to model a bimolecular nucleophilic substitution reaction between potassium hydroxide (KOH) with 1-bromopropane and determine whether it follows a second-order rate law mechanism. A rate constant of 0.0684 M-1 min-1 was obtained for this reaction at 45.1°C, which was determined through equilibrating the reaction and performing titrations of 0.390 M KOH with 0.1000 M hydrochloric acid (HCl). The activation energy calculated from class data was 50.188 kJ/mol, which deviated largely from the literature range value of 72.80–83.76 kJ/mol. It was concluded that the reaction was consistent with the predicted SN2 mechanism, based on the regression of a trendline.

Objective: The objective of this lab is to observe the synthesis of 1-bromobutane in an SN2 reaction, to see how a primary alky halide reacts with an alcohol.

1. Girolmi, G.S.; Rauchfuss, T.B.; Angelici, R.J. Synthesis and Technique in Inorganic Chemistry: A Laboratory Manual. University Science Books, 1999.

Thus, one could safely assume the product from 1-propanol was 1-bromopropane. This is mainly due the C-H wag around 1260cm-1 indication it was a terminal alkyl halide. This reaction went through SN2 mechanism not only because the alcohol was primary but also because there were no rearrangements. If a rearrangement would have occurred, it would have indicated that it was a SN1 mechanism. Further analysis was then done to determine the exact identity of the product and the chemical makeup.

The objective of this experiment is to successfully perform a dehydration of 1-butanol and 2-butanol, also dehydrobromination of 1-bromobutane and 2-bromobutane to form the alkene products 1-butene, trans-2-butene, and cis-2-butene. The dehydration reactions react under and acid-catalysis which follows an E1 mechanism. It was found that dehydration of 1-butanol yielded 3.84% cis-2-butene, 81.83% trans-2-butene, and 14.33% 1-butene, while 2-butanol is unknown due to mechanical issues with the GC machine. For the dehydrobromination, with the addition of a