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Ch.4 - The Study of Chemical Reactions
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook
All textbooksWade 9th EditionCh.4 - The Study of Chemical ReactionsProblem 12c
Chapter 4, Problem 12c

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

c. What is the overall kinetic order?

Verified step by step guidance
1
Step 1: Analyze the given rate law: rate = k_r[cyclohexene][Br_2]^2. This equation shows how the reaction rate depends on the concentrations of cyclohexene and bromine.
Step 2: Identify the exponents in the rate law. The exponent for [cyclohexene] is 1, and the exponent for [Br_2] is 2.
Step 3: Recall that the overall kinetic order of a reaction is the sum of the exponents in the rate law. In this case, add the exponents: 1 (for cyclohexene) + 2 (for Br_2).
Step 4: Interpret the chemical reaction. Cyclohexene reacts with bromine (Br_2) to form a dibrominated cyclohexane product. The unusual rate law indicates a second-order dependence on bromine concentration.
Step 5: Conclude that the overall kinetic order is determined by summing the individual orders of reactants in the rate law.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Rate Law

The rate law of a chemical reaction expresses the relationship between the rate of the reaction and the concentration of its reactants. It is typically formulated as rate = k[A]^m[B]^n, where k is the rate constant, and m and n are the orders of the reaction with respect to reactants A and B. Understanding the rate law is crucial for determining how changes in concentration affect the reaction rate.
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Kinetic Order

The kinetic order of a reaction is the sum of the exponents in the rate law equation. It indicates how the rate of reaction is affected by the concentration of the reactants. In the given rate law, rate = Kr[cyclohexene][Br2]^2, the order with respect to cyclohexene is 1 and with respect to Br2 is 2, leading to an overall kinetic order of 3.
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Bromination of Cyclohexene

Bromination of cyclohexene is an electrophilic addition reaction where bromine (Br2) adds across the double bond of cyclohexene. This reaction can exhibit unusual kinetics under certain conditions, such as the presence of a catalyst or specific solvent effects, which can lead to a rate law that deviates from typical expectations, as seen in the provided rate expression.
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Related Practice
Textbook Question

When a small piece of platinum is added to a mixture of ethene and hydrogen, the ­following reaction occurs: Ethene

Doubling the concentration of hydrogen has no effect on the reaction rate. Doubling the concentration of ethene also has no effect.

a. What is the kinetic order of this reaction with respect to ethene? With respect to hydrogen? What is the overall order?

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Textbook Question

When a small piece of platinum is added to a mixture of ethene and hydrogen, the ­following reaction occurs:

Doubling the concentration of hydrogen has no effect on the reaction rate. Doubling the concentration of ethene also has no effect.

b. Write the unusual rate equation for this reaction.

c. Explain this strange rate equation, and suggest what one might do to accelerate the reaction.

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Textbook Question

The reaction of tert-butyl chloride with methanol

is found to follow the rate equation

rate = kr[(CH3)3C—Cl]

c. What is the kinetic order overall

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Textbook Question

Draw the reaction-energy diagram for the following reverse reaction:

•CH3 + HCl → CH4 + Cl•

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Textbook Question

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

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

4
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Textbook Question

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

a. What is the kinetic order with respect to cyclohexene?

2
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