Rates of Reaction of the Halogenoalkanes Essay

Theory: One of the methods of preparing alkyl halides is via the nucleophilic substitution reactions of alcohols. Alcohols are inexpensive materials and easy to maintain. However, they are a poor leaving group the OH group is a problem in nucleophilic substitution, this problem is fixed by converting the alcohol into H2O.

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.

Abstract: This two part experiment is designed to determine the rate law of the following reaction, 2I-(aq) + H2O2(aq) + 2H+I2(aq) + 2H2O(L), and to then determine if a change in temperature has an effect on that rate of this reaction. It was found that the reaction rate=k[I-]^1[H2O2+]^1, and the experimental activation energy is 60.62 KJ/mol.

Kinetics is the study of the rate of chemical processes. The kinetics of the reaction between crystal violet and NaOH was studied. In order to monitor crystal violet concentration as a function of time, a spectroscopic colorimeter was used. What is the rate law for decolorization of crystal violet? In order to figure this out, the rate of the reaction of crystal violet and sodium hydroxide must be found. In this experiment, the initial goals were to determine the overall rate law for the rate of decolorization of crystal violet in basic solutions as a function of time and to determine the rate law for the reaction including the actual value of k; Rate = k[A]x[B]y. The rate of a reaction was expected to depend on the concentrations

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.

Introduction: The purpose of this experiment is to understand the kinetics of the hydrolysis of t-butyl chloride.The kinetic order of reaction was studied under the effects of variations in temperature, solvent polarity, and structure. It is particularly observed in tertiarhalides i.e. in SN1mechanism, Nucleophilic Substitution which is in 1storder. It is basically a reaction that involves substitution by a solvent that pretendslikea nucleophile i.e. it donates electrons. The reaction being in firstorder means

14) Let the crystals of the silver settle in the plastic container and decant off the liquid.

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 reaction is carried out in saturated aqueous ammonium chloride solution. Thus no special drying of solvents, reagents, or glassware is required. The reaction mechanism for this experiment can be seen below (Fig. 2)

Relative reactivity was also done by taking the reactivity per H of each divided by the reactivity per H of the 1,4 product. All this data points to the fact that the 1,3 product is by far the favored product. As for the reactivity of the carbons, it is observed that in general the further away the chlorine substituent is from the original, the better the yield. In this case however, the one furthest away is not the most yielded. This is because the 1,3 dichlorobutane is at the furthest secondary carbon from the chlorine. The 1,2 and 1,4 products share similar yields likely because the 1,4 is the furthest, but also not secondary, and the 1,2 is secondary but closer to the chlorine, making it have a larger partial positive charge. The 1,1 is formed so little because it is putting a chlorine geminal to the chloro substituent, making it have the highest partial positive charge. Also for the 1,3 product, the radical formed is the most favored radical of the 4 products formed.

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.

However, based on the data obtained in Table 1, Figure 1 shows that all of the chemical substances formed a precipitate, while the tertiary substrate 2-chloro-2-methylpropane formed a precipitate the fastest. This makes sense because as a rule in SN1 reactions, the more stable the carbocation is the faster the reaction will occur. Also, SN1 reactions will prefer tertiary substrates to secondary substrates and secondary substrates to primary substrates. The next substrates to form a precipitate were 2-bromobutane followed by 1-bromobutane. However, it was expected that 2-chlorobutane would form a precipitate before 1-bromobutane because 2-chlorobutane is a secondary substrate, and therefore has a more stable carbocation. The reason that this occurred is because bromine is a better leaving group than chlorine, which allows it to bind easier with the silver ion. The reactions that formed the heaviest precipitate were 2-bromobutane, 1-bromobutane, and 2-chloro-2-methylpropane. This is because these reactions occurred at a faster rate and therefore, generated more of a product than 2-chlorobutane and 1-chlorobutane, which only formed a precipitate upon cooling from the warm water bath.

The purposes of this experiment were to model a bimolecular nucleophilic substitution reaction between potassium hydroxide (KOH) with 1-bromopropane and determine whether it follows a second-order rate law mechanism. A rate constant of 0.0684 M-1 min-1 was obtained for this reaction at 45.1°C, which was determined through equilibrating the reaction and performing titrations of 0.390 M KOH with 0.1000 M hydrochloric acid (HCl). The activation energy calculated from class data was 50.188 kJ/mol, which deviated largely from the literature range value of 72.80–83.76 kJ/mol. It was concluded that the reaction was consistent with the predicted SN2 mechanism, based on the regression of a trendline.

This lab consisted of the conversion of alcohols into alkyl halides through common substitution methods. These methods include SN1 and SN2 mechanism, both of which can occur for this type of reaction. For both reactions, the first step of protonation will be to add hydrogen to the –OH group and then the rest of the reaction will proceed according to the type of mechanism. SN1 reactions form a cation intermediate once the H2O group leaves, then allowing a halide (such as Br) to attack the positively charged reagent1. On the other hand, SN2 reactions are one-step mechanism in which no intermediate is formed and the halide attaches as the leaving