Electrophilic Aromatic Substitution Reaction Lab Report

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.

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.

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 purpose of this experiment was to determine the relative reactivities of different types of hydrogen atoms toward bromine atoms. Although the tested compounds were all arenes, their reactivities differ as they contain different types of hydrogens. The hydrogens could be of three different types and could also differ in being bonded to carbons that are attached to a different number of other carbons. The three different types of hydrogens that could be found were aromatic, aliphatic, and benzylic. The first category is aromatic hydrogens, which are attached to sp2 carbons or are those directly bonded to an aromatic ring. Aromatic hydrogens are the least reactive of the hydrogens in this experiment. The second type of hydrogen being investigated is aliphatic hydrogens, which are found bonded to an SP3 hybridized carbon which are bonded to another SP3 hybridized carbon. Aliphatic hydrogens can also be broken down into further categories according to their number of substituents into primary (less reactive), secondary (more reactive), and tertiary (most reactive). The third type of hydrogens are benzylic hydrogens, which are bonded to a SP3 hybridized carbon that is bonded to a benzene ring. Benzylic hydrogens are also broken into primary and secondary categories according to their substituents, and are all more reactive than aliphatic and aromatic hydrogens.

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.

For the first part of this experiment, six dry test tubes were obtained and labeled accordingly to test the following halides: 2-chlorobutane, 2-bromobutane, 1-chlorobutane, 1-bromobutane, 2-chloro-2-methylpropane, and bromobenzene. To each of the six test tubes 2ml of 15% sodium iodide in acetone was added. 4 drops of the appropriate halide was added to the test tube labeled for that specific halide. After adding the halide, the test tube was then shaken to mix thoroughly. If a precipitate formed the time it took was recorded. Since none of the solutions formed a precipitate at room temperature after five minutes, the test tubes were placed inside of a hot bath at about 50°C. After one minute, the test tubes were taken out of the hot bath and allowed to cool. If any test tubes formed a precipitate, the time it took was recorded on a table.

This experiment is based on the concept of performing SN2 reactions and analyzing how different factors affect said reactions. The factors in question for this experiment are steric hindrance, nucleophilicity, and nature of the leaving group. An SN2 reaction is a type of substitution reaction. A substitution reaction entails an alkyl having its leaving group (typically a halogen) replaced by a different atom. A nucleophilic substitution involves a nucleophile attacking a leaving group on a carbon atom. The nucleophile utilizes its lone pair of electrons to form a new bond with the carbon atom. There are two different types of substitution reactions. There are SN1 reactions (first order) and SN2 reactions (second order) (Weldegerima 2016). SN1 reactions are unimolecular and involve two separate steps. One of the two steps takes longer than the other and is called the rate limiting step. SN1 reactions tend to favor tertiary alkyl halides. SN2 reactions involve a strong nucleophile interacting with an electrophile carbon and making the leaving group detach from the

In a 25-mL round-bottom flask, 1-chlorobutane (5 mL, 4.32 g, 0.046 mol), sulfuryl chloride (1.6 mL, 2.7 g, 0.02 mol), 2,2’-azobis-(2-methylpropionitrile) (0.03 g), and a boiling chip were added. After a condenser and gas trap were attached to the flask, the mixture was heated to a gentle reflux in a steam bath for 20 min. The flask was then allowed to cool down quickly in an ice bath for a short time before a second portion of the 2,2’-azobis-(2-methylpropionitrile) (0.03 g) was added to the flask. The mixture was refluxed for another 10 min. before the flask was cooled in a beaker of water. The reaction mixture was then poured into a small separatory funnel already filled with water (10 mL),

5.3 mL of bromobenzne and 15 mL of anhydrous ether was then placed into the separatory funnel and was shaken and vented in order to mix the solution. Half of the bromobenzene solution was added first into the round bottom flask and as soon as a color change was observed, the remaining half of the bromobenzene was added drop wise into the round bottom flask. The mixture was then refluxed on a heating mantle for 10 minutes until most of the magnesium has been consumed.

Aromatic compounds can undergo electrophilic substitution reactions. In these reactions, the aromatic ring acts as a nucleophile (an electron pair donor) and reacts with an electrophilic reagent (an electron pair acceptor) resulting in the replacement of a hydrogen on the aromatic ring with the electrophile. Due to the fact that the conjugated 6π-electron system of the aromatic ring is so stable, the carbocation intermediate loses a proton to sustain the aromatic ring rather than reacting with a nucleophile. Ring substituents strongly influence the rate and position of electrophilic attack. Electron-donating groups on the benzene ring speed up the substitution process by stabilizing the carbocation intermediate. Electron-withdrawing groups, however, slow down the aromatic substitution because formation of the carbocation intermediate is more difficult. The electron-withdrawing group withdraws electron density from a species that is already positively charged making it very electron deficient. Therefore, electron-donating groups are considered to be “activating” and electron-withdrawing groups are “deactivating”. Activating substituents direct incoming groups to either the “ortho” or “para” positions. Deactivating substituents, with the exception of the halogens, direct incoming groups to the “meta” position. The experiment described above was an example of a specific electrophilic aromatic

Dispense .5 mL water into the already weighed conical vial, replace cap and face insert on its down side.

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.

Free Radical Chain Reactions: Bromination of Arenes Introduction The purpose of this experiment was to observe the relative rates of bromination of different cyclic hydrocarbons. The hydrocarbons toluene, ethyl benzene, t-butyl benzene, cyclohexane, and methyl cyclohexane underwent a timed free radical substitution reaction with bromine under two conditions: room temperature and under a light source. The rate data of the results under these two conditions were compared. In addition, the results were also compared to predicted relative rates that were based on hydrogen properties.

From the above data the decomposition of benzoyl peroxide was slower at lower temperatures for both the C=O and RO=OR groups. Though as the temperature was increased the amount of decomposition also increased resulting in smaller amounts of C =O and RO= OR being detected though the use of an IR. While an larger amount of these two groups were detected for the temperatures around 101C and 113C in comparison to the control which was taken.