aldol reaction Essay

The objective of this lab was to create a ketone through an oxidation reaction using a using a secondary alcohol and oxidizing agent in order to use that ketone in a reduction reaction with a specific reducing agent to determine the affect of that reducing agent on the diastereoselectivity of the product. In the first part of this experiment, 4-tert-butylcyclohexanol was reacted with NaOCl, an oxidizing agent, and acetic acid to form 4-tert-butylcyclohexanone. In the second part of this experiment, 4-tert-butylcyclohexanone was reacted with a reducing agent, either NaBH4 in EtOH or Al(OiPr)3 in iPrOH, to form the product 4-tert-butylcyclohexanol. 1H NMR spectroscopy was used to determine the cis:trans ratio of the OH relative to the tert-butyl group in the product formed from the reduction reaction with each reducing agent. Thin-layer chromatography was used in both the oxidation and reduction steps to ensure that each reaction ran to completion.

To transition from an alcohol to an alkene, the alcohol must be dehydrated with the help of an acid through a reaction known as an E1 mechanism.1 The first step of an E1 reaction is the formation of a carbocation intermediate. This carbocation is produced by the removal of a halogen or a substituted group.2 In this experiment, the hydroxy (OH ) group of the alcohol is removed and this produces the carbocation. The OH- group is removed due to the presence of phosphoric acid. The phosphoric acid is used in the process of adding an additional H+ to the OH- group on the alcohol and assists the OH- in leaving, making the reaction an acid catalyzed dehydration. Another reagent used along with phosphoric acid is heat, which is often used in acid catalyzed dehydration.1

In this laboratory experiment a synthesis was performed through several separate steps. The purpose of the experiment was to synthesize tetraphenylcyclopentadienone from benzaldehyde and to run reactions on carbonyl containing compounds. There was a total of three steps that led up to the synthesis of the final product, tetraphenylcyclopentadienone. The first step of the experiment was the condensation of benzaldehyde to yield benzoin. Thiamine catalyst along with water and ethanol were added to the benzaldehyde, then NaOH was added until the solution turned yellow. After recrystallization, the product was benzoin. Step two was the oxidation of benzoin to benzil.

While RAAS can be good for blood pressure maintenance there are some drawbacks. Angiotensin II can cause structural changes of the heart and blood vessels. It can be implicated hypertrophy and remodeling within the heart. Aldosterone also has adverse effects. Like angiotensin II, aldosterone can cause cardiac remodeling as well as a decreased reuptake of norepinephrine in the heart. This can increase the chances of dysrhythmias (Burchum 472). In a healthy heart these adverse effects would not be seen, but in a heart already in dysfunction, it can cause further complications. The mechanism of action several drugs is to control the outcome of this system.

To begin the reaction, 1.008g of Maleic anhydride was added to a 25ml Erlenmeyer flask. Next, roughly 4.0mL of Ethyl acetate was added to flask. The flask containing Maleic anhydride and Ethyl acetate was shaken to dissolve solid. Then, 4.0mL of Petroleum ether was poured into the into the same flask. Finally, 1.0mL of Cyclopentadiene was carefully added to the other substances. Following the addition of Cyclopentadiene produced an immediate but short-lived boiling, along with the release of heat for a brief period. A white solid began to form, signaling that recrystallization was underway, and the flask was left to cool to room temperature to continue this process. A Cloudy white liquid with sediment appeared to form after about 15 minutes.

An error in the experiment was the low percent yield, which states that impurities occurred. Therefore, if the reaction time was increased there would not be as much excess reactant. Another improvement would be to decrease the proportion of ethanol, which would increase the amount of crystal formation. Although, the impurities will be the same, the yield will be higher. Allowing more time for the reaction mixture to cool would be beneficial because the crystals would not be formed immediately but over a period of time. Another improvement may be to increase drying time because the low percent yield may indicate that the crystals were still

The aldol addition reaction, may involve the nucleophilic addition of a ketone enolate to an aldehyde. Once created, the aldol product loses a molecule of water to form an a, B-unsaturated carbonyl compound which is called aldol condensation. A variety of nucleophiles may be in the aldol reaction, involving the enols, enolates, and enol ethers of ketones, aldehydes, and many carbonyl compounds. The electrophilic partner is more than likely an aldehyde or ketone. When nucleophile and electrophile are different, the reaction is called a crossed aldol reaction; on the contrary, the reaction is called an aldol dimerization when the nucleophile and electrophile are the same.

Friedel-Crafts acylation of anisole with acetic anhydride was used in this experiement to synthesize 4-methoxyacetophenone with the use of a reflux apparatus. Friedel-Crafts reactions can be done by alkylation, which involves mixing an alkyl or acyl halide with a Lewis acid, or acylation, which is done with acid chlorides or anhydrides(Lefevre). Acylation was used because it does not have as many disadvantages aklyations reactions have such as polyalkylation, second electrophilic attacks, and the rearrangement of alkyl carbocation electrophile (McMurry). Acylation reactions require molar amounts of a Lewis catalyst, in our case Aluminum Chloride (AlCl 3) was used (Arata, Nakamura, & Shouji).

Ishaan Sangwan Experiment 9: Aldol Condensation Discussion In this experiment, an aldol condensation reaction will be performed using two different carbonyl compounds to form a beta-hydroxy carbonyl compound. Specifically, acetophenone and p-anisaldehyde will react to form trans-p-anisalacetonphenone. An aldol condensation reaction is an addition reaction that consists of one of the carbonyl compounds being converted into an enol or enolate, and attacking the second carbonyl carbon to form a C-C bond. An enol is a hydrocarbon with a double bond, with an alcohol group on one of the double bond carbons.

In this reaction, a base deprotonates a proton from diethyl malonate to generate an enolate. The enolate then attacks ethyl bromide to form a new carbon-carbon bond. After that, hydrolysis of the ester occurs to give two carboxylic acids, in which one is removed during decarboxylation to give the final product as butyric acid.

The yield for the intermediate was 0.2 g, which is less than half of the theoretical yield. This low yield could be observed from the TLC used to monitor the reaction. TLC plates showed after 40 minutes of refluxing there was both of the reagents present, however, product was forming (Figure 1). TLC after 1 hour showed more of the reactants had been consumed and greater amount of product formed (Figure 1), but due to time constraints the reflux could not be carried out longer. This low yield lead to a down-scaling of the amount of final product that could be synthesized.

At first, Thiocarbohydrazide(2mmol) was dissolve in 40ml of water, then aldehyde( or ketone) (1.5mmol) was dissolve in ethanol (4-6 ml) with acetic acid glacial (1-2 drop). The ethanolic solution was added to aqua solution during 1h at room temperature. The reaction mixture was then stirred for 3-6 h at room temperature (TLC monitoring). Precipitate is filtered and washed with plenty of water. (product 3a-p)

Table 1 organizes all observational and statistical data throughout the experimentation. Mass and volume amounts from various reagents were based upon these values and therefore are insignificant in a table. Each beginning, intermediate, and final product demonstrated shows the initial mass recorded before the next reactionary process began. At the end of each experimentation set, a dollop of sample was utilized to examine IR peaks and melting point range. The IR peaks displayed are the peaks present in the experimental samples that support the pure identity of the product. General observations during and after procedures were noted and are displayed above.

a) In this one there is reaction goes with SN1 reaction mechanism, since there is given tertiary alkyl halide and first there is formation of carbocation and the incoming nucleophile can attack form both side, so there is formation of racemic mixture with enantiomers R and S as follow -

To establish the role of each unit, the coupling reaction of 2-chlorobenzaldehyde (1 mmol), dimedone (1 mmol) and indole (1 mmol) in the presence of the catalyst (0.01 g) was investigated in ethanol at 80 ºC. Although Fe3O4@SiO2-PEG/NH2 acted very efficiently and produced 2-((2-chlorophenyl) (1H-indol-3-yl) methyl) -3-hydroxy-5,5-dimethylcyclohex-2-enone within 15 min in 88% yield, all attempts to produce the product in the presence of Fe3O4@SiO2-PEG and Fe3O4@SiO2-NH2 were not successful. In these cases, the reaction did not go to completion after 90 min, and the product was contaminated by the generation of an abundance of products such as bisindole, and the desired crossed adduct side