The butyl ethanoate ester can only be synthesised during the reflux stage. The ester will continue to be synthesised from the butanol and ethanoic acid until the point where the absence of the limiting reagent prevents further condensation from taking place. Butanol can be considered as the limiting reagent, preventing the total yield of butyl ethanoate which is obtained. Once all of the butanol has been consumed through the reaction with ethanoic acid, the reaction will continue in the reverse direction in an attempt to rejuvenate the supply of butanol. The reverse of condensation is referred to as hydrolysis, a chemical process which produces and alcohol and carboxylic acid when an ester is reacted with water in acidic conditions. In the …show more content…
According to Le Châtelier's principle, if the conditions are altered while the system is at equilibrium, then the reaction will proceed in such a way as to counteract the change. It is possible to utilise the principles of Le Châtelier's to increase the final yield of butyl ethanoate. As the ester is only synthesised during reflux, the only opportunity to improve the yield of butyl ethanoate is during this stage of heating. In order to improve the yield, the theory of Le Châtelier's principle can be utilised, manipulating the conditions to produce an increased yield of ester. It is possible to achieve this desired affect by increasing the concentration of the limiting reagent butanol while the system is at equilibrium. According to the principle, the system will attempt to counteract this change by decreasing the concentration of butanol, causing the system to favour the reactant-consuming direction. As a results, an increased yield of the butyl ethanoate ester would be obtained. Furthermore, according to the Collision Theory, increasing the concentration of the reactant so that there are more molecules per unit area would increase the likelihood of collisions occurring between the reactants. Therefore the likelihood of the collision being successful in the correct orientation with the sufficient internal energy needed to overcome the activation energy barrier would
Therefore, simply mixing equal amounts of the starting materials will convert only about 67% of the starting material into a product. To drive the equilibrium forward Le Chatelier's principle is used, in this case there are two ways to adjust reagent concentrations to force isopentyl alcohol to become isopentyl acetate. One way is to remove the product as it forms. The other way is to use a large amount of acetic acid. This experiment is based on the latter approach, but it raises two issues.
For this experiment, we reduced a ketone to a secondary alcohol. During the first week, everyone ran the reaction using 9-fluoreneone. The ketones for week 2 were derivatives of acetophenone, and my group elected to test the differences in reactivity between acetophenone, 4-methyl-acetophenone, and 4-bromo-acetophenone. We hypothesized that the differences in reactivity would be affected by the electronegativity of substituent. Therefore, we predicted that the 4-bromoacetophenone react the fastest since bromine is a more electronegative substituent, followed by 4-methyl-acetophenonoe, and acetophenone.
In this experiment several reactions were performed in order to differentiate between aldehydes, ketones, and also to identify the unknown compound given. The first reaction was using the Tollens reagent with formaldehyde, acetaldehyde and butanone. The Tollens test was positive for formaldehyde and acetaldehyde, since aldehydes and tollens reagent is the only reaction that will be positive with a precipitate of silver mirrors. In contrast, butanone s a ketone, which with tollens reagent will not result in a silver mirror. Then the same procedure was followed but instead of Tollens reagent, dilute permanganate was used.
The ether formed from the reaction holds about 1.5% water. A brine (saturated NaCl solution) wash is used to try and prevent water from being in the ether to get a pure product. Steric hindrance can also play a role in this reaction causing either one product or both to form. Steric hindrance is the stopping of a chemical reaction which might be caused by a molecule's structure. It causes steric effects to arise from the fact that each atom within a molecule occupies a certain amount of space. If atoms are brought too close together, there is an associated cost in energy due to overlapping electron clouds and this may affect the molecule's preferred shape and reactivity. Steric hindrance occurs when the size of groups within a molecule prevents chemical reactions that are observed in related smaller molecules. Although steric hindrance is sometimes a problem, it can also be a very useful tool to change the reactivity pattern of a molecule by stopping unwanted side-reactions. Steric hindrance between adjacent groups can also restrict torsional bond
Chemical Equilibrium October 14, 2017 Introduction This lab is centered around Le Chatelier’s Principle. In his research, he found that a chemical reaction can be manipulated to maximize yield. A change in one of the variables that describe a system at equilibrium produces a shift in the position of the equilibrium that counteracts the effect of this change.
2.1.9 Temperature. Temperаture affects the stability of the emulsion as follows: by increasing the temperature decreases the stability of the emulsion, since the mechanical strength of adsorption membranes, particulаrly
Aims: To determine the rate constant of a chemical reaction in different solvent mixtures. To observe and account for the change in reaction rates when different solvent system are used.