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Questions and Answers
In a reaction where the rate is first order with respect to an organic compound and zero order with respect to hydroxide ions, what can be inferred about the role of hydroxide ions in the reaction mechanism?
In a reaction where the rate is first order with respect to an organic compound and zero order with respect to hydroxide ions, what can be inferred about the role of hydroxide ions in the reaction mechanism?
- Hydroxide ions inhibit the reaction by reacting with the organic compound in a side reaction.
- Hydroxide ions act as a catalyst, not being consumed in the reaction.
- Hydroxide ions participate in a fast step after the rate-determining step. (correct)
- Hydroxide ions participate in the rate-determining step.
If a reaction's rate equation shows it is first order with respect to both an organic compound and hydroxide ions, what does this indicate about the reaction mechanism?
If a reaction's rate equation shows it is first order with respect to both an organic compound and hydroxide ions, what does this indicate about the reaction mechanism?
- The reaction proceeds through a multi-step mechanism with a slow initial step involving only the organic compound.
- The reaction occurs in two steps, with the hydroxide ions catalyzing the reaction in the second step.
- The reaction involves a single-step mechanism where the organic compound and hydroxide ions collide directly. (correct)
- The reaction requires a high activation energy due to the repulsion between the organic compound and hydroxide ions.
Consider two reactions where a bromine atom is replaced by a hydroxide group in an organic compound. If one reaction is first order with respect to the organic compound only, and the other is first order with respect to both the organic compound and hydroxide ions, what major mechanistic difference can be inferred?
Consider two reactions where a bromine atom is replaced by a hydroxide group in an organic compound. If one reaction is first order with respect to the organic compound only, and the other is first order with respect to both the organic compound and hydroxide ions, what major mechanistic difference can be inferred?
- The first reaction is faster due to the absence of hydroxide ions in the rate-determining step.
- The first reaction likely involves a carbocation intermediate, while the second involves a direct displacement. (correct)
- The second reaction requires a higher temperature to proceed due to the involvement of two reactants in the rate-determining step.
- The first reaction occurs in non-polar solvents, while the second requires polar solvents.
In a reaction where a hydroxide ion replaces a bromine atom, how does the electronegativity difference between carbon and bromine influence the reaction mechanism when the reaction is first order with respect to both reactants?
In a reaction where a hydroxide ion replaces a bromine atom, how does the electronegativity difference between carbon and bromine influence the reaction mechanism when the reaction is first order with respect to both reactants?
A researcher observes that increasing the concentration of hydroxide ions significantly speeds up a fast step in a reaction but has no noticeable effect on the overall rate. What does this suggest about the role of the hydroxide ions in the reaction mechanism?
A researcher observes that increasing the concentration of hydroxide ions significantly speeds up a fast step in a reaction but has no noticeable effect on the overall rate. What does this suggest about the role of the hydroxide ions in the reaction mechanism?
Which statement best describes a reaction mechanism?
Which statement best describes a reaction mechanism?
In a multi-step reaction, what primarily determines the overall reaction rate?
In a multi-step reaction, what primarily determines the overall reaction rate?
Consider the reaction: 2-bromo-2-methylpropane reacting with hydroxide ions. If the concentration of hydroxide ions is significantly increased, what effect will this have on the rate of the overall reaction?
Consider the reaction: 2-bromo-2-methylpropane reacting with hydroxide ions. If the concentration of hydroxide ions is significantly increased, what effect will this have on the rate of the overall reaction?
In the reaction between 2-bromo-2-methylpropane and hydroxide ions, which step is most likely the rate-determining step?
In the reaction between 2-bromo-2-methylpropane and hydroxide ions, which step is most likely the rate-determining step?
What does a curly arrow represent in a reaction mechanism?
What does a curly arrow represent in a reaction mechanism?
If a reaction mechanism involves two steps, one with a high activation energy and another with a low activation energy, which step is likely to be the rate-determining step?
If a reaction mechanism involves two steps, one with a high activation energy and another with a low activation energy, which step is likely to be the rate-determining step?
Consider a reaction where the rate-determining step involves the breaking of multiple bonds and the formation of only one bond. What can be inferred about the reaction rate?
Consider a reaction where the rate-determining step involves the breaking of multiple bonds and the formation of only one bond. What can be inferred about the reaction rate?
Which of the following is LEAST likely to be included in a description of a reaction mechanism?
Which of the following is LEAST likely to be included in a description of a reaction mechanism?
Flashcards
Rate Equation
Rate Equation
Describes how the rate of a chemical reaction depends on the concentration of reactants. Found experimentally.
Rate-Determining Step
Rate-Determining Step
The slowest step in a multi-step reaction, determining the overall reaction rate.
First-Order Reaction
First-Order Reaction
Reaction rate is directly proportional to the concentration of one reactant.
Zero-Order Reaction
Zero-Order Reaction
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One-Step Reaction
One-Step Reaction
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Reaction Mechanism
Reaction Mechanism
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Reaction Stages
Reaction Stages
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Overall Reaction
Overall Reaction
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Curly Arrow
Curly Arrow
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Measured Rate
Measured Rate
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Carbon-Bromine Bond Breaking
Carbon-Bromine Bond Breaking
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Hydroxide Ion
Hydroxide Ion
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Study Notes
- A reaction mechanism details the steps of a reaction, clarifying how bonds break and form.
Reaction with 2-bromo-2-methylpropane
- The overall reaction replaces a bromine atom with an OH group in an organic compound.
- The carbon-bromine bond breaks in a small proportion of the organic compound, forming ions.
- Carbon-bromine bonds are strong, making this change slow.
- High concentration of hydroxide ions leads to a fast reaction, forming a new covalent bond between carbon and oxygen.
- Carbon-oxygen bonds are strong, which makes the OH group tends to stay attached. -This reaction occurs in two steps with differing rates: one slow and one fast.
Rate Determining Step
- The overall rate of a reaction is controlled by the rate of the slowest step.
- In the prior reaction, the hydroxide ion cannot combine with the positive ion until it has formed.
- The slow step of a reaction is known as the rate determining step.
- Measuring the rate of a reaction is actually measuring the rate of the rate determining step.
- For the given reaction, rate = k[(CH3)3C-Br].
- It is first order with respect to the organic compound and zero order with respect to the hydroxide ions.
- Hydroxide ion concentration does not affect the overall reaction rate, indicating it participates in a later, fast step.
- Increasing hydroxide ion concentration speeds up the fast step but doesn't affect the overall reaction rate, which is governed by the slow step.
Reaction of CH3CH2Br with OH-
- Rate = k[CH3CH2-Br][OH-].
- This reaction is first order with respect to both the organic compound and the hydroxide ions.
- Both components participate in the slow step, requiring a straightforward collision.
- The carbon atom hit by the hydroxide ion has a slight positive charge, and the bromine has a slight negative charge due to electronegativity differences.
- As the hydroxide ion approaches, the bromine is displaced in one smooth action.
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Description
Explore reaction mechanisms with 2-bromo-2-methylpropane. The reaction involves replacing a bromine atom with an OH group, proceeding in two steps: one slow and one fast. The overall reaction rate is determined by the slowest step, known as the rate-determining step.
