Addition reactions are a common chemical transformation of a carbon-carbon double bound. Carbon-carbon double bonds contain one pi bond, which is held together weakly, and one sigma bond. The weak pi bond of the alkene, like 1-hexene, can be broken if a strong base is added. The electrophile, aka the base, attacks the nucleophile of the molecule. A covalent bond forms between the base and the carbon, which is an exothermic and favorable reaction. In this specific experiment, 1-hexene and HBr were added to each other to see if 2-bromohexane would form as product. Markonikov’s rule would be followed, and product 2-bromohexane would be formed, if the solution when silver nitrate was added turned a pale yellow color. The point of this experiment …show more content…
was to synthesize bromohexane from 1-hexene and HBr using distillation, an important purification method, to isolate the product. It was also important to determine whether the product was a differentiation of secondary or primary bromines using chemical tests to assess whether Markovnikov’s rule was followed.
Markovnikov’s Rule states that “when a Bronsted acid, HX, adds to an unsymmetrically substituted double bond, the acidic hydrogen of the acid bonds to that carbon of the double bond that has the greater number of hydrogen atoms already attached to it.” There is preferential substitution, which is called regioselectivity. This is when a protic acid is added to an alkene, its halide binds to more substituted carbon and its hydrogen will bind to the smallest substituted carbon. HBr is immiscible with an alkene, so mixing them would form two separate layers. Along with this, HBr is a very strong acid, and its conjugate acid in an aqueous solution (H3O+) won’t protonate the …show more content…
alkene. So, a phase transfer catalyst is necessary for the HBr to go from an aqueous phase to an organic phase. Tetrabutyl ammonium bromide is added to the mixture of HBr and 1-hexene, and it’s purpose is to dehydrate the HBr and make it more reactive with hexane. This would allow the electrophile to attack the nucleophile. Following Markonikov’s law, the bromine and hydrogen are added to 1-hexene and the end product is 2-bromohexane.
In order for the reflux to work well, rapid stirring must be in effect throughout. The yield of 2-bromohexane is higher when the reaction mixture is stirred. This is because when HBr is alone, it is immiscible in 1-hexene. Stirring with tetrabutyl ammonium bromide causes separation of organic and aqueous layers. When the aqueous layer is removed, we make it more reactive with alkene. Then stirring solution causes more surface area for the HBr and 1-hexene to react with each other, so more product of 2-bromohexane forms. Separating reagents between phases is important and can be contributed to total surface area. In order to increase the surface area, the reaction must be stirred to stimulate colloids and droplets of immiscible layers. If no mixture occurs, no formation of two distinct layers will occur and the organic portion product will have low content because HBr may have reaction with water and produced a weak acid H3O+. Phase transfer catalysts, like tetrabutyl ammonium bromide are amphoteric. The ammonium salt removes HBr from an aqueous phase and puts it in an organic
phase. The organic layer is then separated and dried with anhydrous sodium sulfate, then filtered using micro scale filtering to come up with final product. The product is tested using silver nitrate and sodium iodide acetone tests to see what alkyl halide are produced. Silver nitrate test tests for bromine in product, and sodium iodide acetone test reacts at temperatures to determine whether primary or secondary. The silver nitrate test should turn a pale yellow to show existence of bromide and sodium iodide test should precipitate when heated to show that it is a secondary bromide when following Markovnikov’s rule.
As a final point, the unknown secondary alcohol α-methyl-2-naphthalenemethanol had the R-configuration since it reacted the fastest with S-HBTM and much slower with R-HBTM. TLC was a qualitative method and ImageJ served as a quantitative method for determining which reaction was the faster esterification. Finally, 1H NMR assisted in identifying the unknown from a finite list of possible alcohols by labeling the hydrogens to the corresponding peaks.
2-bromobutene also undergoes a similar mechanism as 2-butanol, Hoffman E2 reaction, producing 1-butene as the major product. However since 2-bromobutene is less satirically hindered than 2-butanol more 2-trans-butene will be formed.
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,
The unknown bacterium that was handed out by the professor labeled “E19” was an irregular and raised shaped bacteria with a smooth texture and it had a white creamy color. The slant growth pattern was filiform and there was a turbid growth in the broth. After all the tests were complete and the results were compared the unknown bacterium was defined as Shigella sonnei. The results that narrowed it down the most were the gram stain, the lactose fermentation test, the citrate utilization test and the indole test. The results for each of the tests performed are listed in Table 1.1 below.
The goal of this two week lab was to examine the stereochemistry of the oxidation-reduction interconversion of 4-tert-butylcyclohexanol and 4-tert-butylcyclohexanone. The purpose of first week was to explore the oxidation of an alcohol to a ketone and see how the reduction of the ketone will affect the stereoselectivity. The purpose of first week is to oxidize the alcohol, 4-tert-butylcyclohexanol, to ketone just so that it can be reduced back into the alcohol to see how OH will react. The purpose of second week was to reduce 4-tert-butylcyclohexanol from first week and determine the effect of the product's diastereoselectivity by performing reduction procedures using sodium borohydride The chemicals for this lab are sodium hypochlorite, 4-tert-butylcyclohexanone
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
Alcohol, which is the nucleophile, attacks the acid, H2SO4, which is the catalyst, forming oxonium. However, the oxonium leaves due to the positive charge on oxygen, which makes it unstable. A stable secondary carbocation is formed. The electrons from the conjugate base attack the proton, henceforth, forming an alkene. Through this attack, the regeneration of the catalyst is formed with the product, 4-methylcyclohexene, before it oxidizes with KMnO4. In simpler terms, protonation of oxygen and the elimination of H+ with formation of alkene occurs.
Triphenylmethyl Bromide. A 400 mL beaker was filled with hot water from the tap. Acetic acid (4 mL) and solid triphenylmethanol (0.199 g, 0.764 mmol) were added to a reaction tube, with 33% hydrobromic acid solution (0.6 mL) being added dropwise via syringe. The compound in the tube then took on a light yellow color. The tube was then placed in the beaker and heated for 5 minutes. After the allotted time, the tube was removed from the hot water bath and allowed to cool to room temperature. In the meantime, an ice bath was made utilizing the 600 mL plastic beaker, which the tube was then placed in for 10 minutes. The compound was then vacuum filtered with the crystals rinsed with water and a small amount of hexane. The crude product was then weighed and recrystallized with hexane to form fine white crystals, which was triphenylmethyl bromide (0.105 g, 0.325 mmol, 42.5%). A Beilstein test was conducted, and the crystals produced a green to greenish-blue flame.
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.
Benzyl bromide, an unknown nucleophile and sodium hydroxide was synthesized to form a benzyl ether product. This product was purified and analyzed to find the unknown in the compound.
...eases, including temperature. It is determined from the data that the reaction is more likely to have a step wise mechanism than a concerted due to the small – ΔS and a relatively large value of ΔH from the tables. Due to some errors, it is best to perform another experiment for future protocols. In addition with the variance the 35°C where at one point the absorbance levels off and then increases. In comparison to the rate constant against temperatures, at 25°C it is higher than 35 and 45. More test is required to ensure proper determination of the rate constant at those temperatures.
-The participate movement within the bowl tends to mix components quickly owing to high shear forces and the expansion in bed volume which allows diffusive mixing.
Catalysts are most often used to speed up the chemical reaction. I tried to do some preliminary work but each time the reaction went either to fast or to slow which meant in the experiment I wouldn't get accurate results. I decided to use the same amounts of hcl acid and ...
Substrate 1 and 2 both formed turbidity, although substrate 2 reacted faster because it is a better leaving group due to its increased size. Substrate 8 occurred immediately although it is only a secondary bromine due to bromine being such a good leaving group as well as because the silver acts as a great catalyst. Substrate 3 did not react due to the lack stability in terms of surrounding steric
The catalytic process occurs at lower temperature anf offers higher selectivity but requires frequent regeneration of the catalyst. Then, the products are cooled and introduced into a pair of separators which separate the unreacted hydrogen. The unreacted hydrogen is compressed and recycle back to the feed and reactor. The products that leaving the separators are heated before introduced into a distillation column which the toluene is separated from the stream and recycle back to the...