The better leaving group is Bromine. From the SN1 reactions, all alkyl bromides, with the exception of Bromobenzene, produced precipitates at room temperature. Although only the first tube in the SN2 reactions produced precipitate at room temperature, the back side attack happened where expected. It is notable, that in the SN¬2 reaction, eventually all alkyl bromides produced precipitate still with the exception prior. Chlorine as a leaving group has a higher activation energy. First observing the periodic table, Chlorine has a smaller electron cloud that Bromine – forming closer bonds which in turn require more energy to break. This is apparent in both substitution mechanisms, as most of the alkyl chlorides only formed precipitate when introduced to a heat. Exclusive to SN2, 2-chlorobutane did not form any precipitate when introduced to heat, going against the grain for what was expected in this reaction. This scenario was seen across much of the class data; a possible indicator of a contaminated solution. Bulkier substrates hindered the speed of reaction, confirming that the less accessible the target carbocation is from the nucleophile the less reactive they will be. Consider the equation of reaction kinetics… Rate=k[substrate][solvent], The structure of the substrate will determine the …show more content…
It is not uncommon to have error in an experiment as it is more rare to have no error that it is to obtain some. To give some insight as to why these were observed we must consider the process of the experiment, the inevitable human error, and the possibility of unfortunate events. Due to the repetitive nature of this experiment it is not a difficult task to have forgot which halide solutions were introduced into which tubes and double reactions might have occurred. The most likely however is that there were contaminates introduced to the false positive SN1 Bromobenzene and the false negative SN2
When 1-bromobutane is reacted with potassium t-butoxide there is only one product formed, 1-butene. This is because the halide is on a primary carbon thus producing only one product.
Then the reaction tube was capped but not tightly. The tube then was placed in a sand bath reflux to heat it until a brown color was formed. Then the tube was taken out of the sand bath and allowed to cool to room temperature. Then the tube was shaken until a formation of a white solid at the bottom of the tube. After formation of the white solid, diphenyl ether (2 mL) was added to the solution and heated until the white solid was completely dissolved in the solution. After heating, the tube was cooled to room temperature. Then toluene (2 mL) was added to the solution. The tube was then placed in an ice bath. Then the solution was filtered via vacuum filtration, and there was a formation of a white solid. Then the product was dried and weighed. The Final product was hexaphenylbenzene (0.094 g, 0.176 mmol,
Enantiomers, a type of isomer, are non-superimposable, mirror images of each other. Diasteriomers, another type of isomer, are non-superimposable, non-mirror images of each other. Dimethyl maleate and dimethyl fumarate are diasteriomers, as they are not mirror images but instead vary in the orientation of the carbomethoxy groups around the double bond. Dimethyl maleate is the cis-isomer because both groups are on the same side and dimethyl fumarate is the trans-isomer because the two groups are on opposite sides. A bromine free radical mechanism was required for this conversion. First, energy from light is required to create two bromine free radicals from Br2. Then one of the free radicals attacks the double bond in dimethyl maleate, breaking it and creating a carbon radical on the other carbon. The bond then rotates and reforms, freeing the bromine radical and creating the trans-isomer, dimethyl fumarate. Bromine in this reaction is acting as a catalyst in this reaction and then cyclohexane is added at the end to neutralize the bromine free radicals. The activation reaction of the radical reaction is lower than the activation energy of the addition reaction, which is why it occurred more quickly. This reaction was successful because the percent yield was 67.1%, which is greater that 65%. It also demonstrated the expected principles, as the reaction did not occur without the presence of both light and bromine. The dimethyl fumarate had a measured boiling point of 100C to 103C, which is extremely close to the expected boiling point of 102C to
This experiment was divided into two main steps. The first step was the addition of bromine to trans-stilbene. Trans-stilbene was weighted out 2.00g, 0.0111mol and mixed with 40ml of glacial acetic acid in 100ml Erlenmeyer flask on a hot bath. Pyridinium hydrobromide perbromide of 4.00g, 0.0125mol was added carefully into the flask.
Figure 1: Initial anti attack approach of bromine to the bottom side of the trans-cinnamic acid:
The product was recrystallized to purify it and the unknown filtrate and nucleophile was determined by taking the melting points and performing TLC. Nucleophilic substitution reactions have a nucleophile (electron pair donor) and an sp3 electrophile (electron pair acceptor) with an attached leaving group. This experiment was a Williamson ether synthesis usually SN2, with an alkoxide and an alkyl halide. Conditions are favored with a strong nucleophile, good leaving group, and a polar aprotic solvent.
This experiment was performed in order to compare the ability of bromine atoms to react with hydrogen atoms of different classifications. The experiment compared aromatic, aliphatic and benzylic hydrogen atoms of primary, secondary, and tertiary classifications. The time it took for the reaction to occur was measured and compared between the different hydrocarbons. This rate of reaction was used to determine the reactivity of the various hydrogen atoms on the hydrocarbons with bromine.
The purpose of this experiment is to examine the reactivity of different compounds. To accomplish this, different types of benzene (aniline, acetanilide, phenol, or anisole) will be brominated. The reactivity and activation strength will determine of the compound is polyhalogenated, or monohalogenated. In this experiment it is to be predicted in which order the reaction substitution(s) will occur and the reactivity order of each of the benzene compounds. The product will then be analyzed and identified by recrystalling and comparing the melting point of isolated product to literature values.
In this experiment, four elimination reactions were compared and contrasted under acidic (H2SO4) and basic (KOC(CO3)3) conditions. The acid-catalyzed dehydration was done on 2-butanol and 1-butanol; a 2ᵒ and 1ᵒ alcohol, respectively. The base-induced dehydrobromination was performed on 2-bromobutane and 1-bromobutane; isomeric halides. The stereochemistry and regiochemistry of the four reactions were analyzed by gas chromatography (GC) to determine product distribution (assuming that the amount of each product in the gas mixture is proportional to the area under its complementary GC peak. The three butene products have been verified that they elute in the following order: 1-butene, trans-2-butene, and cis-2-butene.
The hypothesis of the reaction, there was similarity by comparing the compound in case nitrogen was neutral and protonated. Table (1) illustrated that there was clearly different in the energy between two cases of that compound by 119 kJ/mole with basis set 6-311+G(d,p) and 128 kJ/mole with basis set 6-31 G(d) and similarly in level of theory(B3LYP). Therefore, the protonated nitrogen of the HALS molecule had higher energy than the neutral nitrogen through the potential energy of the reaction. Accordingly, the hypothesis that was reported becomes incorrect against to the calculation result found it from Gaussian program.
Chemical kinetics is a branch of chemistry that involves reaction rates and the steps that follow in. It tells you how fast a reaction can happen and the steps it takes to make complete the reaction (2). An application of chemical kinetics in everyday life is the mechanics of popcorn. The rate it pops depends on how much water is in a kernel. The more water it has the quicker the steam heats up and causes a reaction- the popping of the kernel (3). Catalysts, temperature, and concentration can cause variations in kinetics (4).
Predictions may be made about the suitability of possible catalysts by assuming that the mechanism of catalysis consists of two stages, either of which can be first:
First, put on safety goggles to protect the eyes from the chemicals used in this experiment. To begin the lab, label one 100-mL beaker “HCl” using a beaker marker and add 30 mL of 1.0 M Hydrochloric acid solution to this beaker. Next, label the other 100-mL beaker “Na2S2O3” and pour 30 mL of 0.30 M Sodium thiosulfate solution. Finally, label the 250-mL beaker “H2O” and add 25 mL of Distilled or deionized water into this beaker. After all the beakers have been labeled and filled with their set solutions, place a sheet of white paper underneath the six-well reaction plate and using the black sharpie, draw a “X” under each of the wells. Before beginning the lab, place the six-well reaction plate over the sheet and verify that the six “X’s” can be seen through the plate.
My lab partner and I investigated what would happen if certain solids and liquids were mixed together, and whether or not it produced a chemical reaction. To use in our investigation we had baking soda (sodium bicarbonate), calcium chloride, water, and phenol red. I hypothesized that if we combined these solids and liquids in different ways, then they would sometimes produce chemical reactions because the substances had chemical properties that would make them prone to react with one another. For example, baking soda contains sodium, while calcium chloride contains both calcium and chlorine. I knew that Chlorine, a halogen, reacts with calcium or sodium, as they are alkaline earth and alkali metals respectively. The evidence we found supported my hypothesis. When various chemicals were combined, they produced chemical reactions, which could be identified by signs like change in color, heat produced, or gas production.
There is also the potential of human error within this experiment for example finding the meniscus is important to get an accurate amount using the graduated pipettes and burettes. There is a possibility that at one point in the experiment a chemical was measured inaccurately affecting the results. To resolve this, the experiment should have been repeated three times.