Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions

Bruice8th EditionOrganic ChemistryISBN: 9780135213711Not the one you use?Change textbook

Bruice 8th Edition

Ch. 22 - Catalysis in Organic Reactions and in Enzymatic Reactions

Problem 9

Chapter 23, Problem 9

The relative rate of reaction for the cis alkene (E) is given in Table 22.2. What do you expect the relative rate of reaction for the trans alkene to be?

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Understand the context: The problem involves comparing the relative rates of reaction for cis and trans alkenes. Cis and trans isomers differ in their spatial arrangement, which can influence their reactivity due to steric and electronic effects.

Review the data in Table 22.2: Locate the relative rate of reaction for the cis alkene (E) in the table. This value will serve as a reference point for comparison with the trans alkene.

Consider steric effects: Cis alkenes typically have substituents on the same side of the double bond, leading to greater steric hindrance. Trans alkenes, with substituents on opposite sides, generally experience less steric hindrance, which can affect their reactivity.

Analyze electronic effects: The spatial arrangement of substituents in cis and trans alkenes can also influence the stability of the transition state during the reaction. Trans alkenes often have a more favorable transition state due to reduced steric strain.

Predict the relative rate: Based on the steric and electronic considerations, hypothesize whether the trans alkene will react faster or slower than the cis alkene. Use the relative rate of the cis alkene as a benchmark to estimate the relative rate of the trans alkene.

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Key Concepts

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

Cis and Trans Isomerism

Cis and trans isomerism refers to the geometric isomers of alkenes, where 'cis' indicates that substituents are on the same side of the double bond, while 'trans' indicates they are on opposite sides. This spatial arrangement affects the physical and chemical properties of the compounds, including their reactivity.

Reaction Mechanisms of Alkenes

The reaction mechanisms of alkenes often involve electrophilic addition, where the double bond acts as a nucleophile. The stability of the intermediate carbocation formed during the reaction can influence the rate of reaction, with more substituted alkenes typically reacting faster due to greater stability.

Steric Hindrance

Steric hindrance refers to the repulsion between bulky groups in a molecule that can impede reactions. In the case of alkenes, the spatial arrangement of substituents can affect how easily reactants approach the double bond, influencing the overall rate of reaction for cis versus trans isomers.

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