6. Thermodynamics and Kinetics

Under certain conditions, the bromination of cyclohexene follows an unusual rate law:

b. What is the kinetic order with respect to bromine?

How will the rate of the reaction between bromomethane and hydroxide ion be affected if the following changes in concentration are made?

b. The concentration of the alkyl halide is cut in half and the concentration of the nucleophile is not changed.

Given the following rate data, how many molecules are in the rate-determining step of this reaction?

Given that step 1 of the following reaction is rate determining, write the rate law for the overall reaction.

Within the following pairs, pick which reaction you would expect to be faster based on having a higher value of the frequency factor (A).

(a)

Parts (a)–(f) of this assessment refer to the rotation around the single bond of ethane.

(a) Given that the rate of the reaction is independent of concentration, fill in the missing rates in the following table.

How will the rate of the reaction between bromomethane and hydroxide ion be affected if the following changes in concentration are made?

a. The concentration of the alkyl halide is not changed and the concentration of the nucleophile is tripled.

For rotation around a bond, the rate constant is equal to the reaction rate. Why?

The rate constant for the uncatalyzed reaction of two molecules of glycine ethyl ester to form glycylglycine ethyl ester is 0.6 M^-1 s^-1. In the presence of Co²⁺, the rate constant is 1.5 × 10⁶ M^-1 s^-1. What rate enhancement does the catalyst provide?

The rate constant for a reaction can be increased by ______ the stability of the reactant or by ______ the stability of the transition state.

From the Arrhenius equation, predict how

a. increasing the experimental activation energy affects the rate constant for a reaction.

From the Arrhenius equation, predict how

b. increasing the temperature affects the rate constant for a reaction.

Consider the following reaction-energy diagram.

a. Label the reactants and the products. Label the activation energy for the first step and the second step.

b. Is the overall reaction endothermic or exothermic? What is the sign of ΔH°?

c. Which points in the curve correspond to intermediates? Which correspond to transition states?

d. Label the transition state of the rate-limiting step. Does its structure resemble the reactants, the products, or an ­intermediate?

The rate of the reaction of methyl chloride with hydroxide ion is linearly dependent on both the concentration of methyl chloride and the concentration hydroxide ion. At 30 °C, the constant (k) for the reaction is 1.0 × 10^-5 M^-1 s^-1

b. If the concentration of methyl chloride is decreased to 0.010 M, what will be the effect on

1. the rate of the reaction?

2. the rate constant for the reaction?

When ethyl bromide is added to potassium tert-butoxide, the product is ethyl tert-butyl ether.

CH₃CH₂–Br + (CH₃)₃C–O^–K⁺ → (CH₃)₃C–O–CH₂CH₃ ethyl bromide potassium tert-butoxide ethyl tert-butyl ether

a. What happens to the reaction rate if the concentration of ethyl bromide is doubled?