Nucleophilic Substitution Lab Report

860 W. S. Hamama, A. E. E. Hassanien, M. G. El-Fedawy, and H. H. Zoorob Vol 54

SN1 reactions are considered unimolecular nucleophilic substitution mechanisms and are a first-order process. Meaning that the reaction forms a carbocation intermediate and that the concentration of the nucleophile does not play a role in the rate-determining step, which is the slowest step in the reaction. All of the SN1 reaction mechanisms in this procedure can react two different ways. The expected mechanism for these reactions would be that the carbocation would react with the weak nucleophile nitrate, attaching the nitrogen to the positively charged carbon. However, while nitrate is the intended nucleophile in all of the reactions, it is a poor nucleophile. The ethanol used in this reaction is a polar protic ionizing solvent,

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

of the Sn1 reactions are alkyl halides and alcohols respectively. When a hydrogen atom is

In this experiment 2,3-dimethyl-2, 3-butanediol was treated with aqueous sulfuric acid in order to identify the major product. This was done using IR and NMR spectroscopy. Based on the structure of the reactant and product, as well as acid-catalyzed reactions of alcohol functional groups, a mechanism was proposed for the reaction. While carrying out the simple distillation it was important to collect the distillate and monitor the temperature change. Once the distillation was complete there were two phases, in this case the top layer contained the desired product. In order to dry the liquid MgSo4 was used this was carefully decanted in order to obtain yield of product, IR, and NMR. When analyzing the IR there were major peaks at 2970 meaning

Both SN1 and SN2 reactions are nucleophilic substitution reactions. The main difference is their rate-determining step. For SN1 reaction, the rate-determining step is unimolecular where for SN2 reaction is bimolecular. In this experiment, an intermediate is formed. After the halide has been completely removed and the nucleophile has been added, the reaction terminates and leads to an inversion of stereochemistry. SN2 reaction is favoured because it gives a product with predictable stereocenter as it proceeds through an inversion of

Organic sulfoxides, especially diphenyl sulfoxide (Ph2SO), are useful synthetic reagents (Kaczorowska et al., p. 8315). Diphenyl sulfoxide has been used in catalytic oxidation of alkyl sulfides to sulfoxides (Arterburn & Nelson, p.2260). They also play an important role as therapeutic agents. Examples include anti-ulcer, antibacterial, antifungal, anti-therosclerotic, anthelmintic, antihypertensive, and cardiotonic agents, as well as, psychotonics and vasodilators (Kaczorowska et al., p. 8315). Diphenyl sulfoxide is also used as a reagent in the formation of glycosidic bonds (Garcia, Pool, & Gin, p.1). This involves an in situ

The nucleophilic substitution SN1/SN2 typically occur in a competitive regime. There are various conditions that define the predominant reaction mechanism taking place. Since SN1 leads to the racemic mixture, SN2 is more popular in asymmetric organic synthesis. So, detailed computational studies of model SN2 reactions have been carried out during the last three decades[2-6, 9].

In base promoted dehydration, the second method of transforming an alcohol to an alkene, is based on the same concept. The leaving group must be turned stable to be able to become a good leaving group. The difference between the two possible reactions is that base promoted is not reversible. It is not able to be reacted with the alkene in the opposite process. In addition, base promoted and E2 elimination reactions are favorable only when the acidic medium is not able to proficiently complete the reaction. In times when the acid is not able to proceed the reaction, there are certain factors that are used that are able to yield desirable products. Issues seen when a molecule is reacted with a strong acid unexpected rearrangement of carbocations can arise. Moreover, double bond migrations can appear sometimes in the presence of strong acids; however, because this is able to occur during hydrogenation, a base can reduce the occurrence of the migration. There are also changes in the stereochemistry that can possibly occur, as well as side reaction materials such as ethers. When these issues are faced, base promoted elimination is a better way for the reaction to be continued. As previously mentioned, acid catalyzed as well as base promoted must be able to create the hydroxy group into a good leaving group by protonation. According to base promoted reactions, the base that is consumed is

Analyzing and Determining Subsitution Reactions Through SN1 & SN2 reactions involving Alcohol-Containng Compounds to verify production and succsess of alkyl halides.

The synthesis of the methylcyclohexene products from 2-methylcyclohexanol occurs through an E1, unimolecular elimination reaction. The first step in this reaction mechanism involves the protonation of the alcohol group in the starting material. The oxygen of this alcohol performs a nucleophilic attack on a hydrogen from the phosphoric acid and gains a positive charge. Then, the pronated alcohol, which is now a good leaving group, leaves the cyclohexane ring and creates a positive charge on the carbon to which it was

In this experiment, Conversion of Alcohol to Alkyl Halides and alcohol is converted to an alkyl halide through SN1 or an SN2 mechanism. This is done by using 1-propanol and 2-pentantol with HBr, Hydrobromic acid. Only half of the groups will use 1-propanol, and 2-pentantol. All results are analyzed using NMR and IR.

Experiment 7 introduces the concept of “dehydrohalogenation”. The idea is that alkyl halides may undergo elimination reactions which involve Brønsted–Lowry bases. In this event, a halide anion and a proton are lost to form a new π bond. There are two common types of elimination reactions: either unimolecular (E¬1) (the rate determing step) or bimolecular (E2). E1 elimination reaction is a two step mechanism which requires the formation of a carbonium ion intermediate by the splitting of the leaving group (the halide in this case). After this formation, a loss of a proton (H+) causes a π bond to form. We want the the carbonium ion to be as stable as possible. This ensures that it forms easily as well as increases the rate of the E1 reaction. On the other hand, E2 elimination reactions are a one step mechanism in which a simultaneous removal of a proton by the base leads to the loss of the leaving group, thus generating a new π bond. In this part of the experiment,

1.Explain the mechanisms of [nucleotide excision repair] and [translesion synthesis], and the main differences between the two. Also include a concise comparison of the enzyme activities involved in the two processes.

In order for any elimination reaction to occur, there must be an alkyl halide and a base that will extract a proton. Depending on whether or not the base is strong, will determine which elimination reaction it will undergo. First, the leaving group must be identified. The leaving group is an alkyl halide. The carbon that the alkyl halide is attached to is called the alpha carbon. The next carbon connected to the alpha carbon is the beta carbon. The beta carbon will have beta hydrogens attached to it. The leaving group must first leave. Then the base of the reaction will extract one of the beta hydrogens. When the hydrogen is removed, it leaves the carbon with two valence electrons because of heterolysis. Heterolysis is when both elections from a bond cleavage remain with the bigger, more electronegative atom (Pillai, 26). Since the carbon has two valence