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Ch.4 - The Study of Chemical Reactions
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728Non è quello che usi tu?Cambia libro di testo
Tutti i libri di testoWade 9th EditionCh.4 - The Study of Chemical ReactionsProblema 34a
Capitolo 4, Problema 34a

The following reaction is a common synthesis used in the organic chemistry laboratory course.

When we double the concentration of methoxide ion (CH3O–), we find that the reaction rate doubles. When we triple the concentration of 1-bromobutane, we find that the reaction rate triples.
a. What is the order of this reaction with respect to 1-bromobutane? What is the order with respect to methoxide ion? Write the rate equation for this reaction. What is the overall order?

Guida verificata passo dopo passo
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Step 1: Analyze the problem and identify the reaction components. The reaction involves 1-bromobutane (CH3CH2CH2CH2Br) and methoxide ion (CH3O–) as reactants, producing methoxybutane (CH3CH2CH2CH2OCH3) and bromide ion (Br–). The reaction rate depends on the concentrations of the reactants.
Step 2: Determine the order of the reaction with respect to 1-bromobutane. The problem states that when the concentration of 1-bromobutane is tripled, the reaction rate also triples. This indicates a first-order dependence on 1-bromobutane. Mathematically, this means the rate is proportional to [CH3CH2CH2CH2Br]^1.
Step 3: Determine the order of the reaction with respect to methoxide ion. The problem states that when the concentration of methoxide ion is doubled, the reaction rate also doubles. This indicates a first-order dependence on methoxide ion. Mathematically, this means the rate is proportional to [CH3O–]^1.
Step 4: Write the rate equation for the reaction. Since the reaction is first-order with respect to both 1-bromobutane and methoxide ion, the rate equation can be expressed as: r=k⋅[CH3CH2CH2CH2Br]1⋅[CH3O]1, where k is the rate constant.
Step 5: Determine the overall order of the reaction. The overall order is the sum of the individual orders with respect to each reactant. Since the reaction is first-order with respect to both 1-bromobutane and methoxide ion, the overall order is 1 + 1 = 2.

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Reaction Order

Reaction order refers to the power to which the concentration of a reactant is raised in the rate law of a chemical reaction. It indicates how the rate of reaction is affected by the concentration of that reactant. For example, if doubling the concentration of a reactant doubles the reaction rate, the reaction is first order with respect to that reactant.
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Rate Law

The rate law is an equation that relates the rate of a chemical reaction to the concentration of its reactants. It is typically expressed in the form Rate = k[A]^m[B]^n, where k is the rate constant, [A] and [B] are the concentrations of the reactants, and m and n are the orders of the reaction with respect to each reactant. Understanding the rate law is essential for determining how changes in concentration affect the reaction rate.
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Overall Reaction Order

The overall reaction order is the sum of the individual orders with respect to each reactant in the rate law. It provides insight into the complexity of the reaction mechanism. For instance, if a reaction is first order with respect to one reactant and second order with respect to another, the overall order would be three. This concept helps in predicting how the reaction rate will change with varying concentrations of reactants.
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