1. Consider the effect of water concentration on rate of the reaction in water and acetone. WOuld you predict that the rate would be greater or less in the presence of a higher concentration of water? Explain your answer, using the structure of the transition state.
2. Consider the following: You accidentally use 50/50 2-propanol/water instead of 50/50 acetone/water mix. Would you predict that the reaction rate would be higher with acetone/water or with 2-propanol/water? Explain reasoning. (Acetone is a polar aprotic solvent and 2-propanol is a polar protic solvent)
1. To predict the effect of water concentration on the rate of a reaction in water and acetone, we need to consider the structure of the transition state. The transition state is the highest-energy intermediate between reactants and products and is where the bond-breaking and bond-forming processes occur.
In general, a high water concentration would favor reactions that involve water molecules in the transition state. Water is a polar solvent that can participate in hydrogen bonding, which can stabilize the transition state and make it easier for the reaction to proceed.
In the case of a reaction in water and acetone, the presence of a higher concentration of water would likely increase the rate of the reaction. Water can interact with the reactant molecules and stabilize the transition state more effectively compared to acetone. Acetone is a polar solvent but it is less capable of forming hydrogen bonds due to its structure.
Therefore, the rate of the reaction is predicted to be greater in the presence of a higher concentration of water.
2. Considering the accidental use of a 50/50 2-propanol/water mixture instead of a 50/50 acetone/water mixture, we need to evaluate the effect of the respective solvents on the reaction rate.
Acetone is a polar aprotic solvent, which means it does not have an active hydrogen atom. On the other hand, 2-propanol is a polar protic solvent, which has active hydrogen atoms.
In reactions involving polar protic solvents, the active hydrogen atoms can participate in hydrogen bonding, leading to stronger interactions between solvent molecules and the reactants. This can increase the solubility of reactants and enhance their reaction rate.
In contrast, polar aprotic solvents like acetone do not have active hydrogen atoms available for hydrogen bonding, resulting in weaker interactions with the reactant molecules. This generally leads to lower solubility and slower reaction rates compared to polar protic solvents.
Therefore, we can predict that the reaction rate would be higher with the acetone/water mixture rather than the 2-propanol/water mixture, given that acetone is a polar aprotic solvent and 2-propanol is a polar protic solvent.