Synthesis Of Dimethyl Tetraphenylphthalate And Dimethyl Acetylene

The Diels-Alder reaction was discovered and named after the Nobel Prize winning scientists Kurt Alder and Otto Diels in 1928. Such a reaction occurs when a diene with two adjacent double bonds is mixed with a dienophile consisting of a double bond in order to create a cyclohexene. The diene must be in the s-cis conformation in order for the electron transfer to engage correctly. If the diene in question is in s-trans conformation then the access to the molecules is limited, thus, no reaction can occur. The dienophile we used was maleic anhydride. Maleic anhydride possesses high electron withdrawing characteristics which caused a very quick reaction. The reaction will

In this experiment, meso-stilbene dibromide was used to produce diphenylacetylene through two sequential dehydrohalogenations. The first part is a concerted E2 mechanism, where the reactant is deprotonated at the beta carbon from the halide ion that will be leaving. This creates a transition state where the leaving hydrogen and halide are anti-periplanar with each other, meaning that they are at a 180° angle in relation to one another. This reaction is caused by a base—in this case, potassium hydroxide—and produces a haloalkene, or vinyl halide. Potassium hydroxide was only added to reaction when needed, as

Objective The objective of this experiment is to prepare a sample of tetraphenylcyclopentadienone through the aldol condensation of benzil and dibenzyl ketone under a basic environment. Procedure Part A- Aldol Condensation of Tetraphenylcyclopentadienone • In a 100 mL round bottom flask, 0.525 g (0.0025 mol) of benzil and 0.525 g (0.0025 mol) of dibenzyl ketone were mixed with an additional 0.075 g (0.002 mol) of potassium hydroxide pellets in a solution of 10 mL of 95% ethanol, and finally a boiling chip was inserted into the solution. The contents of the mixture were allowed to mix, and while this was occurring, a reflux setup was prepared (as illustrated in Figure 1.A) and the round bottom flask was attached to the setup.

The partial positive bromine atom is added to the alkene yielding a bromonium ion intermediate that stabilizes the compound. In the second step, the negatively charged bromide ion behaves like a nucleophile to attack the bromonium ion to open the three-membered ring and add the second bromine. This reaction is an anti-addition reaction because of the steric hindrance caused by the bromonium ion, and therefore two chiral centers are generated with opposite configurations based on the Cahn-Ingold-Prelog nomenclature system. Dehalogenation is a double electrophilic elimination reaction which is the reverse of halogenation. A strong base such as potassium hydroxide to remove a hydrogen and a bromine in an antiperiplanar fashion twice to yield an alkyne.

The goals in this lab were to have a reaction occur with 4-methylcyclohexanol and an acid catalyst to form our product of 4-methylcyclohexene via an E1 reaction. This reaction is accomplished by removing the –OH group on 4-methylcyclohexanol via dehydration and to have a double bond form via a loss of a hydrogen on a β-Carbon.

For this study, each group had the same dienophile, N-methylmaleimide, but different dienes, anthracene-9-methanol or anthracene-9-carboxaldehyde. Initial reaction conducted with anthracene-9-methanol and N-methylmaleimide was successful in generating a generous amount of product; however, due to errors performed during the purification method by recrystallization, some product was lost, thereby resulting in a low yield. Upon completion of the reaction, the Diels-Alder adduct was subjected to analysis by NMR spectroscopy, specifically, Proton NMR. The percent yield of this reaction was expected to be high, however, the reaction yielded a percent yield of 4.88%, which is significantly low. Typically, a low percent yield is an indication of an inefficient reaction; however, in this case, this cannot be concluded due to errors that occurred during the reaction. Theoretically, dienophiles and dienes can have different electron donating and electron withdrawing substituents, thereby changing either can impact the percent yield of the reaction. An electron donating substituents on the diene will increase the percent yield as the chances of the reaction occurring is increased with the increase in the number of electron donating groups. The Reverse is true for dienophiles, as an increase in the number of electron withdrawing groups with lower the energy in the

Figure 4: Reaction 4 [1-bromopentane + K+ -OC(CH3)3 (Potassium tert-butoxide)] and its (theorized) major and minor products are shown. The major product was 1-t-butoxypentane and the minor was 1-pentene (in consecutive order). Note that 1-pentene increases in reaction 4 relative to reaction 3. This is due to steric hindrance (bulky tert-butoxide) which decreases the SN2 product in reaction 4 relative to reaction 3.

A Diels-Alder reaction involves a cyclic flow of electrons in a concerted step in which the conjugated diene, supplies 4 pi electrons and the alkene or alkyne, known as the dienophile, supplies 2 pi electrons. In this process, two new sigma bonds, which link the former dienophile to the diene, and one new pi bond, between the former double bonds on the diene, are formed. Furthermore, the reaction can involve molecules with a large variety of substituents, as long as there is a diene with electron donating groups and a dienophile with electron withdrawing groups as this can speed up the reaction. A critical part of the

The dienophiles can take part in Diels-Alder reactions by either ‘normal demand’ or ‘inverse demand’ Diels-Alder reaction. In ‘normal demand,' Diels-Alder reactions, the dienophiles contain electron-withdrawing group conjugated to the alkenes. In inverse demand, the electron-donating group is in conjugation with

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.

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

In the first step the trialkyl phosphate acts as a nucleophile and, in a typical Sn2 reaction, forms a phosphonium salt. The salt is unstable and a halide ion X displaces R in the Sn2 manner to form a dialkylphosphonate. It is the phosphonate that, in the presence of base, is converted to a Wittig-like reagent. Normally the Wittig reagent is an ylid and neutral, but the modified Wittig is analogous to the carbanion of an aldol intermediate. Due to its resonance forms, the phosphonate anion is able to attack the carbonyl much like acarbanion in an aldol reaction to give an oxyanion species. This is where the analogy with the aldol reaction fails. The oxyanion undergoes a reaction analogous to nucleophilic substitution at an unsaturated center to form the olefin, normally as the E isomer, and a water soluble phosphonate anion. In this particular experiment, diethyl benzylphosphonate is used with benzaldehyde as the carbonyl component. Since phase transfer conditions are used, we can use a weaker base, the hydroxide ion. The reactivity o the anion formed is very high, resulting in excellent yields of trans-stilbene. The trans form of Stilbene is more favored than the sterically hindered cis form. Although

5,5-dimethyl-1,3-cyclohexanedione, or "dimedone" will be prepared using diethyl malonate and distilled mesityl oxide via carbonyl reactions such as Michaels addition and Claisen condensation reactions (Scheme 1).1 Also, the dimedone 13 exists in two forms: keto and enol forms. The form of dimedone will be influenced by the fast equilibrium between the dimedone and the solvent.2 As seen in the dimedone spectra in different concentration of solvent ( spectrum ), the keto-enol forms can be distinguished by comparing their the keto and enol CH3 peaks in the spectra. In addition, the derivatives of dimedone 19, hexahydroacridinedione, will be synthesized from the purified dimedone 13 and p-isopropylbenzaldehyde 14 and ammonium acetate in Scheme 2.

According to the mechanisms suggested before Chauvin, the only possible products are ethylene and tetradeuteroethylene—along with cyclohexene. The pairwise participation of the carbon atoms in the mechanism prevents the formation of 1,2-dideuteroethylene. However, according to the Chauvin mechanism all three ethylene products should be formed and in a statistical ratio 1:2:1.

Aromatic compounds tend to undergo electrophilic aromatic substitutions rather than addition reactions. Substitution of a new group for a hydrogen atom takes place via a resonance-stabilized carbocation. As the benzene ring is quite electron-rich, it almost always behaves as a nucleophile in a reaction which means the substitution on benzene occurs by the addition of an electrophile. Substituted benzenes tend to react at predictable positions. Alkyl groups and other electron-donating substituents enhance substitution and direct it toward the ortho and para positions. Electron-withdrawing substituents slow the substitution and direct it toward the meta positions.