Kinetic versus Thermodynamic Control in Competing Reactions - Lab Report Example

Response to question From the experiment, it is evident that cyclohexanone has a lower activation energy compared to benzaldehyde semicarbazone. This is apparent when the MW for cyclohexanone is recorded as 98.15g/mol and that one of the benzaldehyde as 106.121g/mol. Cyclohexanone semicarbazide is a component having a molecular formula written as C7H13N3O, as well as a molecular weight of about 155.1976. Its two dimension structure could be represented as in diagram 1. Diagram 1. Cyclohexanone semicarbazone adopts a distorted conformation chair with a high total puckering of the rings that are numbered. The compound is normally found in structures that are crystalline. Their C-S bond is similar to the N-N bond which is normally retained in the semicarbazone. This compound has the lowest activation energy. ?G=?H- ?S where ?G is the Gibbs free energy, ?H bonding energy, ?S amount of disorder, and ?G+ activation energy. Because ?S is the minimum for most processes, the term could be assumed to ?G-?H. According to the thermodynamic versus the kinetic control of the compound, the energy reaction is remaining cold due to the small activation energy. When the reaction remains hot, there would be small energy for the compound to return to its initial state. Therefore, the structure of the semicarbonate would be as in diagram 2. Diagram 2. On the other hand, the benzaldehyde semicarbonate’s activation energy is higher than that of Cyclohexanone semicarbazone because the packing of the crystal of the compound C9H11N3OS has stability due to two NH….o bonds of hydrogen. It has an amino acid which does not take part in the classical bond of hydrogen. The group of methyl is identified in two positions having almost similar occupancies. Response to question 2. The compound that is most energetically stable is benzaldehyde semicarbazone. In the experiment, it is observed that benzaldehyde has a higher MW (106.121 compared to that of Cyclohexanone semicarbazone (98.15). It is also observed form the experiment that benzaldehyde semicarbazone has a slightly higher melting point than that of Cyclohexanone semicarbazone. The structure of benzaldehyde semicarbonate is represented as in digram 3. Diagram 3. Whenever benzaldehyde semicarbazone is cooled from a phase of isotropic, the nucleation genesis begins with the domain that is continuous forming planar structures having colour that is deep violet and displays reflections of the specular. The formed texture is the key traits of the cholesteric phase. This implies that the phase may look unstable and could change itself into a semetic phase. Further cooling causes the radical fringes to be displayed on the focal conic fans textures, and such a phase is linked to the phase of chiral smectic. The chiral smetic phase is extremely stable for different types of temperatures. Other homologues of the compound were identified as having different liquid phases that are crystalline. Such compounds display phases of cholesteric whenever they are exposed to high temperature. Response to question 3. Thermodynamic product C A B Kinetic product Diagram 4. Diagram 5. In this reaction whenever the pH is less than seven the reaction would be fast whereas when the pH is greater than seven the reaction would be slow. When the pH is much less than seven the reaction would be extremely slow thus not a nucleophilic reaction. Whenever the temperature is zero degrees Celsius, the reaction would be kinetic controlled, and the kinetic products would be made first. When the temperature of the reaction is about twenty five degrees Celsius, the reaction would form a mixture whereby there would be less energy for the reaction going back. At a temperature of about eighty degrees Celsius, the reaction would be a thermodynamic control reaction. Response to question 4. Kinetic control reaction or thermodynamic control reaction can dictate the reaction composition of a product mixture during the competing of the pathways directed towards different reactions and products. The differentiation is crucial whenever product A is established faster than product B due to their varied energies of activation. The reaction conditions like temperature, solvent, and pressure influence the type of reaction pathway to be taken. This means that these conditions could lead to the thermodynamically controlled pathway or rather the kinetically controlled pathway. Nevertheless, this conditions hold only in a situation where there is a two pathway activation energy in which one of them is higher than the other (Sykes, 8). The existence of kinetic or thermodynamic control leads to the final component of the required product. The competing pathways of reaction result in products that are different. These conditions, therefore, influence the reaction selectivity. In this respect, the products that are kinetic are normally made faster. They take place at a temperature below zero degrees Celsius. In different situations, this could be referred to as 2-adduct since the components are normally added in the second and the first carbon. These products possess a double terminal bond and their reaction is considered to be irreversible. On the other hand, thermodynamic products are made at temperatures that are high especially above 40 degrees Celsius (Sykes, 10). These products are normally referred to as 1, 4 adducts since they do add to the fourth and the first carbons. These products do have a double internal bond and has a reversible reaction. Additionally, when this reaction is done, thermodynamic products are considered to be remarkably stable due to their substitution. A structure of kinetic product is displayed in diagram 6. Diagram 6. At 00C conditions: The differences between the products that are kinetically controlled and those that are thermodynamically controlled is the differences in their energies of activation. When the reaction goes up to completion on a path that is easy, such a path is known as the kinetic pat. Such a path is considered to have low energy of activation meaning that little is needed for the product to be made. However, this product (product A) is not in a form that is stable. After some time, the quantity of thermodynamic product (stable) will increase thus the decrease of product A. This is shown in diagram 7. Diagram 7. Work cited. Sykes, Peter. Mechanism in Organic Chemistry. New York: Pearson Prentice Hall,2008. Print. Read More