Conversion of Alcohol to Alkyl Halides Essay

Two forms of stereochemistry can form product for the bromination of trans-cinnamic acid. Cis addition, also known as syn addition, is one way of forming product. This form of stereochemistry allows for the components of the reagent to add to the same side of the double bond. Trans, also known as anti addition, is the second form of addition that can create product for this experiment. Tran stereochemistry occurs when the components of the reagent add to opposite sides of the double bond. In this experiment, the formation of either erythro-2,3-dibromo-3-phenylpropanoic acid (trans/anti-R,S or S,R) or threo-2,3-dibromo-3-phenylpropanoic acid (cis/syn-R,R or S,S) was expected to occur.

Objective: The objective of this lab is to observe the synthesis of 1-bromobutane in an SN2 reaction, to see how a primary alky halide reacts with an alcohol.

During the halogenation reactions of 1-butanol, 2-butanol, and 2-methyl-2-propanol, there is a formation of water from the OH atom of the alcohol, and the H atom from the HCl solution. The OH bond of the alcohol is then substituted with the Cl atom. Therefore all of the degrees of alcohol undergo halogenation reactions, and form alkyl halides as products. This is because the functional group of alkyl halides is a carbon-halogen bond. A common halogen is chlorine, as used in this experiment.

The objective of this laboratory experiment is to study both SN1 and SN2 reactions. The first part of the lab focuses on synthesizing 1-bromobutane from 1-butanol by using an SN2 mechanism. The obtained product will then be analyzed using infrared spectroscopy and refractive index. The second part of the lab concentrates on how different factors influence the rate of SN1 reactions. The factors that will be examined are the leaving group, Br – versus Cl-; the structure of the alkyl group, 3◦ versus 2◦; and the polarity of the solvent, 40 percent 2-propanol versus 60 percent 2-propanol.

The two remaining sp2 hybrid orbitals on oxygen are used to hold oxygen's lone pairs(bruice). O-ethylsaccharin is then less stable because the Ethyl group is attached to the Oxygen that used to be a carbonyl group, giving the Carbon an sp3 configuration (joined to two other carbons, the Oxygen with the Ethyl group and a Hydrogen). This put strain on the ring, and therefore is less stable.”(Richard y.a.). Upon mixing the reactants, sodium saccharin slightly dissolved producing a clear colorless liquid. When placed at 80°C hot bath, the solution completely dissolved and turned yellowish-green. Iodoethane is a clear and colorless liquid, but when exposed to light and air the Iodide dissociates from ethane and gives off a yellow color as a sign of decomposition. The solution was covered to prevent this from happening. But, as iodide dissociates from CH3CH2 that then gave off its yellowish color which shows SN2 reaction taking place. SN2 reaction happened fast The limiting Reagent is Iodoethane , as the alkylating agent; it was not used in excess and dictated how far the reaction went. The Na+ binds with I-(noted disappearance of the yellow color, as I- binds with Na+) then the ethane group bonds with either the Oxygen of saccharin or the Nitrogen of saccharin. The final product after vacuum filtration had some unreacted material, indicated by some yellow green solid formation.

Which means that it did not have any neighboring hydrogens but it still had a hydrogen on the compound. The next peak was a multiplet around 6-7.1 ppm and had 5 similar hydrogens. According to the H NMR chemical shifts, 5 similar hydrogens and a ppm range from 6-8.0 ppm, this particular peak was an aromatic. More specifically a benzene with 5 similar hydrogens, and with another hydrogen with attached substituents. This aromatic also contains 4 degrees of saturation, satisfying the requirement that the compound needed to have DoU of 4. The next peak was a quartet around 3.4-3.5 with 2 hydrogens. The quartet meant that the compound had 3 neighboring hydrogens and that particular peak was a CH2. The last pear was a triplet around 1.2-1.4 ppm with 3 hydrogens on the compound. The triplet meant that compound that 2 neighboring hydrogens indicating that particular peak was a methyl group (CH3). This help determine that the CH2 and CH3 were bonded to one another creating an ethyl

The solvolysis of t-butyl bromide is an SN1 reaction, or a first order nucleophilic substitution reaction. An SN1 reaction involves a nucleophilic attack on an electrophilic substrate. The reaction is SN1 because there is steric obstruction on the electrophile, bromine is a good leaving group due to its large size and low electronegativity, a stable tertiary carbocation is formed, and a weak nucleophile is formed. Since a strong acid, HBr, is formed as a byproduct of this reaction, SN1 dominates over E1. The first step in an SN1 reaction is the formation of a highly reactive carbocation, in which a leaving group is ejected. The ionization to form a carbocation is the rate limiting step of an SN1 reaction, as it is highly endothermic and has a large activation energy. The subsequent nucleophilic attack by solvent and deprotonation is fast and does not contribute to the rate law for the reaction. The Hammond Postulate predicts that the transition state for any process is most similar to the higher energy species, and is more affected by changes to the free energy of the higher energy species. Thus, the reaction rate for the solvolysis of t-butyl bromide is unimolecular and entirely dependent on the initial concentration of t-butyl bromide.

The solution that was performed in this experiment was to use sulfuric acid in order to form a protonated alcohol, so when the halogen or nucleophile back attacks the compound, water is displaced. Once the alcohol is protonated, the solution reacts in either an SN1 or SN2 mechanism.

The purpose of this experiment is to examine the reactivities of various alkyl halides under both SN2 and SN1 reaction conditions. The alkyl halides will be examined based on the substrate types and solvent the reaction takes place in.

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,

The purpose of this lab is to understand the process of eliminating an alkyl halide to form an alkene. The experiment is carried out by first converting the alcohol, 2-methy-2-butanol, into the alkyl halide of 2-chloro-2-methylbutane that will then be put through dehydrohalogenation that favors elimination reaction (E2) to create a mixture of 2-methyl-2-butene and 2-methyl-1-butene. A fractional distillation will be taken to purify the mixture and an additional gas chromatography will be done to further analyze the mixture composition. A bromide test will be done to determine the product of an alkene in the experiment.

For this experiment, nucleophilic substitution was first observed. The 2-methyl-2-butanol was converted into 2-chloro-2-methylbutane by using an SN1 reaction. The alcohol on the 2-methyl-2-butanol was a tertiary alcohol. To form a good leaving group since the hydroxide ion is a bad leaving group, the tertiary alcohol was protonated with HCl, but since it consists of a fully substituted carbon atom from the carbon oxygen bond, an SN2 displacement cannot occur. Therefore, water is the leaving group that disassociates and leaves a relatively stable tertiary carbocation behind.

The reason is the chlorine which is a good leaving group, and the nitrate which a weak nucleophilic. Also, the carbocation will be more stable due to resonance. In SN2, it formed a participation after 10 sec and complete formation after 1 minute and 5 sec. That’s mean this compound is reactive in SN2. There reason it is a primary alkyl halide.

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

The purpose of this lab was to discover the effects that an alkyl group and solvent have on the rate of SN1 and SN2 reactions. Two separate mechanisms can be used to perform the nucleophilic substitution of alkyl halides: SN1 and SN2. A SN1 reaction, or unimolecular displacement, is a 1st order, nucleophilic substitution that involves two steps. The rate law for this reaction, Rate = k[Rx], doesn’t include the nucleophile in it.1 These two step reactions have a carbocation intermediate. SN1 reactions work best when the central carbon has as many bulky groups surrounding it as possible. These substituents increase the possibility of the carbocation intermediate forming by increasing the steric strain of the molecule. This idea is which causes a carbocation intermediate to develop in reactions of secondary or tertiary alkyl halides, and a primary alkyl halide to not be able to go through a SN1 reaction. The carbocation intermediate that forms is a sp2 carbon that allows the nucleophile to attack from both sides of the molecule. If neither attack is favored, they both occur equally, making it a racemic mixture. The solvent of choice for the SN1 reactions are both polar and protic, because a solvent that will not react with the carbocation intermediate is needed, since this will give an unwanted product. In polar protic solvents you get a hydrogen atom that is very highly polarized since it is attached to an electronegative atom, because of this it can interact