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Chapter 27: Problem 10

Answer the following questions for this \(\mathrm{S}_{\mathrm{N}}1\) reaction: (a) What is the rate expression for the reaction? (b) Draw the reaction profile for the reaction. Label all parts. Assume that the products are lower in energy than the reactants. (c) What is the effect on the rate of the reaction of doubling the concentration of 1-bromo-1-methylpentane? (d) The solvent for the reaction is ethanol. What is the effect on the rate of the reaction of adding more ethanol?

Short Answer

Expert verified
(a) The rate expression for the reaction is \(Rate = k [1-bromo-1-methylpentane]\). (b) The reaction profile starts with the reactants at a higher energy level, peak at the transition state, and come down to products that are at a lower energy level. (c) The rate of reaction doubles if the concentration of 1-bromo-1-methylpentane is doubled. (d) More ethanol does not affect the rate of reaction as the reaction is dependent only on the concentration of the substrate.

Step by step solution

01

Determine the Rate Expression

For an SN1 reaction, the rate of reaction is only dependent on the concentration of the substrate, in this case, 1-bromo-1-methylpentane. The rate expression is given by: \(Rate = k [1-bromo-1-methylpentane]\)
02

Draw the Reaction Profile

In an energy diagram for an SN1 reaction, the reactants start at a higher energy level, then there's a hump to represent the transition state, following which the energy level comes down to the products. Since the products are lower in energy than reactants, the change in energy (\(ΔE\)) is negative.
03

Effect of Doubling Concentration of Substrate

In an SN1 reaction, the rate is proportional to the concentration of the substrate. Therefore, if the concentration of 1-bromo-1-methylpentane is doubled, the rate of reaction will also double.
04

Effect of Adding More Solvent

In an SN1 reaction, the solvent helps in stabilizing the intermediate carbocation and also helps in breaking the bond of the substrate. Adding more ethanol, in this case, will not affect the rate of the reaction as the reaction is unimolecular and rate of reaction is independent of the concentration of solvent.

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