Table of contents

1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

8. Elimination Reactions

Cumulative Substitution/Elimination

Organic Chemistry

8. Elimination Reactions

Cumulative Substitution/Elimination

Previous problemNext problem

1:14 minutes

Problem 29

Textbook Question

Which of the following two compounds eliminates HBr more rapidly in a basic solution?

Verified step by step guidance

Step 1: Analyze the structures of the two compounds (a and b). Both compounds contain a chlorine atom attached to a secondary carbon, and an oxygen atom with lone pairs. The elimination of HBr in a basic solution typically follows an E2 mechanism, which requires a strong base and a good leaving group.

Step 2: Consider the stereoelectronic requirements for the E2 elimination mechanism. The β-hydrogen (the hydrogen on the carbon adjacent to the carbon bonded to chlorine) must be anti-periplanar to the leaving group (Cl). This geometry is crucial for the elimination reaction to proceed efficiently.

Step 3: Examine the spatial arrangement of the β-hydrogen and the chlorine atom in both compounds. In compound (a), the β-hydrogen and chlorine are positioned in a way that allows for an anti-periplanar relationship, facilitating elimination. In compound (b), the geometry may be less favorable due to steric hindrance or a lack of proper alignment.

Step 4: Evaluate the effect of the oxygen atom in both compounds. The oxygen atom in compound (a) may stabilize the transition state through its lone pairs, making elimination more favorable. In compound (b), the oxygen atom's position might not contribute as effectively to stabilization.

Step 5: Conclude that the rate of elimination depends on the alignment of the β-hydrogen and chlorine, as well as the stabilization of the transition state. Compound (a) is likely to eliminate HBr more rapidly due to its favorable anti-periplanar geometry and potential stabilization effects.

Verified video answer for a similar problem:

This video solution was recommended by our tutors as helpful for the problem above

Video duration:

Play a video:

Was this helpful?

Key Concepts

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

Elimination Reactions

Elimination reactions involve the removal of a small molecule, such as HBr, from a larger molecule, resulting in the formation of a double bond. In organic chemistry, these reactions can occur via different mechanisms, such as E1 or E2, which depend on the structure of the substrate and the reaction conditions. Understanding the mechanism is crucial for predicting the rate of elimination and the stability of the resulting alkenes.

Basic Conditions

Basic conditions in organic reactions typically involve the presence of a strong base, which can facilitate the elimination of hydrogen halides like HBr. In a basic environment, the base can abstract a proton from the substrate, promoting the formation of a double bond. The strength and sterics of the base can significantly influence the reaction pathway and rate, making it essential to consider when analyzing elimination reactions.

Substituent Effects on Reactivity

The presence and position of substituents on a molecule can greatly affect its reactivity in elimination reactions. Electron-withdrawing groups can stabilize the transition state, while steric hindrance can either facilitate or hinder the elimination process. In the compounds presented, the arrangement of chlorine and hydrogen atoms will influence the rate of HBr elimination, making it important to analyze how these substituents interact with the base during the reaction.

Watch next

Master Intro to Substitution/Elimination Problems with a bite sized video explanation from Johnny

Start learning

Related Videos

Related Practice

Textbook Question

Explain how each of the following changes affect the rate of the reaction of 1-bromobutane with ethoxide ion in DMF.

a. The concentration of both the alkyl halide and the nucleophile are tripled.

b. The solvent is changed to ethanol.

Textbook Question

Explain how the following changes affect the rate of the reaction of 2-bromo-2-methylbutane with methanol:

a. The alkyl halide is changed to 2-chloro-2-methylbutane.

b. The alkyl halide is changed to 2-chloro-3-methylbutane.

Textbook Question

The following substitution reaction, between a strong base and a 1° haloalkane, occurs in a single step via backside displacement. Yet it is not technically an S_N2 reaction. Why?

Textbook Question

Propose a mechanism for each of the following reactions:

Textbook Question

Propose a mechanism for the following reaction. (Hint: The rate of the reaction is much slower if the nitrogen atom is replaced by CH.)

Textbook Question

Show a mechanism for the following elimination reactions. Label the mechanism as E1 or E2.

(d)

Textbook Question

Paying close attention to the stereochemical outcome, predict the product of these elimination reactions.

(d)

Textbook Question

Predict the product(s) that would result when molecules (a)–(p) are allowed to react under the following conditions: (i) SOCl₂ ; (ii) PBr₃ ; (iii) SOCl₂ , NEt₃ (iv) 1. TsCl, Et₃N 2. NaCN; (v) 1. TsCl, Et₃N 2. NaOt-Bu (vi) H₂SO₄ (vii) HCl; (viii) HBr; (ix) PCC; (x) H₂CrO₄ , H₂O (xi) HOCl, H₂O (xii) HIO₄ If no reaction occurs, write 'no reaction.'

(c)

Show more practices

Download the Mobile app

Privacy

Do not sell my personal information

Accessibility

Patent notice

Sitemap