Ch.4 - The Study of Chemical Reactions

Wade9th EditionOrganic ChemistryISBN: 9780135213728Not the one you use?Change textbook

Wade 9th Edition

Ch.4 - The Study of Chemical Reactions

Problem 11c

Chapter 4, Problem 11c

The reaction of tert-butyl chloride with methanol

is found to follow the rate equation
rate = k_r[(CH₃)₃C—Cl]
c. What is the kinetic order overall

Verified step by step guidance

Step 1: Analyze the given rate equation, rate = Kr[(CH3)3C—Cl]. This indicates that the rate of the reaction depends only on the concentration of tert-butyl chloride ((CH3)3C—Cl).

Step 2: Recall the definition of reaction order. The reaction order is determined by the sum of the exponents of the concentration terms in the rate equation. In this case, the exponent for [(CH3)3C—Cl] is 1.

Step 3: Note that methanol (CH3OH) is present in the reaction but does not appear in the rate equation. This suggests that the reaction rate is independent of the concentration of methanol, confirming that the reaction is unimolecular.

Step 4: Recognize that this type of reaction is characteristic of an SN1 mechanism, where the rate-determining step involves the formation of a carbocation intermediate from tert-butyl chloride.

Step 5: Conclude that the overall kinetic order of the reaction is 1, as the rate depends solely on the concentration of tert-butyl chloride.

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Key Concepts

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

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group (like Cl in tert-butyl chloride) by a nucleophile (like methanol). In this case, the reaction follows an SN1 mechanism due to the stability of the tert-butyl carbocation formed during the reaction. Understanding this mechanism is crucial for analyzing the reaction's kinetics and products.

Rate Law and Kinetic Order

The rate law expresses the relationship between the rate of a chemical reaction and the concentration of its reactants. In this case, the rate equation is given as rate = Kr[(CH3)3C—Cl], indicating that the reaction is first-order with respect to tert-butyl chloride. The overall kinetic order is determined by summing the exponents in the rate law, which in this case is 1.

Energy Diagram

An energy diagram visually represents the energy changes during a chemical reaction, including the activation energy and the transition states. The diagram for the reaction of tert-butyl chloride with methanol would show the formation of the carbocation intermediate and the energy barrier that must be overcome for the reaction to proceed. This understanding helps in grasping the reaction's mechanism and its rate.

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Related Practice

Textbook Question

The reaction of tert-butyl chloride with methanol

is found to follow the rate equation

rate = k_r[(CH₃)₃C—Cl]

a. What is the kinetic order with respect to tert-butyl chloride?

3202

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Textbook Question

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

c. What is the overall kinetic order?

948

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Textbook Question

a. Using bond-dissociation enthalpies from Table 4-2. (page 167), calculate the heat of reaction for each step in the free-radical bromination of methane

b. Calculate the overall heat of the reaction.

1818

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Textbook Question

The reaction of tert-butyl chloride with methanol

is found to follow the rate equation

rate = k_r[(CH₃)₃C—Cl]

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

1281

views

Textbook Question

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