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

16. Conjugated Systems

Conjugated Hydrohalogenation (1,2 vs 1,4 addition)

Organic Chemistry

16. Conjugated Systems

Conjugated Hydrohalogenation (1,2 vs 1,4 addition)

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5:15 minutes

Problem 25b

Textbook Question

Predict the products of the following reactions.
(b) cyclopentadiene + anhydrous HCl

Verified step by step guidance

Step 1: Recognize the type of reaction. Cyclopentadiene is a conjugated diene, and anhydrous HCl is a strong acid. This reaction involves electrophilic addition, where HCl adds across the double bonds of cyclopentadiene.

Step 2: Identify the electrophile and nucleophile. In HCl, the H⁺ ion acts as the electrophile, and the Cl⁻ ion acts as the nucleophile. Cyclopentadiene has two double bonds that can act as nucleophiles.

Step 3: Determine the regioselectivity of the addition. The proton (H⁺) will preferentially add to the carbon of the double bond that leads to the most stable carbocation intermediate. In cyclopentadiene, this typically results in the formation of a resonance-stabilized carbocation.

Step 4: Add the nucleophile (Cl⁻) to the carbocation. Once the carbocation is formed, the chloride ion (Cl⁻) will attack the positively charged carbon, completing the addition reaction.

Step 5: Predict the final product. The addition of HCl across one of the double bonds in cyclopentadiene will result in a chlorinated cyclopentene derivative. Consider stereochemistry and regioselectivity when predicting the structure of the product.

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Key Concepts

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

Electrophilic Addition

Electrophilic addition is a fundamental reaction mechanism in organic chemistry where an electrophile reacts with a nucleophile, resulting in the formation of a new bond. In the case of cyclopentadiene and anhydrous HCl, the double bonds in cyclopentadiene act as nucleophiles, attacking the electrophilic hydrogen in HCl, leading to the formation of a more stable product.

Cyclopentadiene Structure

Cyclopentadiene is a cyclic diene with two conjugated double bonds. Its structure allows for unique reactivity patterns, particularly in electrophilic addition reactions. The presence of these double bonds makes cyclopentadiene highly reactive, enabling it to undergo various transformations, including the addition of HCl.

Markovnikov's Rule

Markovnikov's Rule states that in the addition of HX to an alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This principle helps predict the regioselectivity of the reaction products when cyclopentadiene reacts with HCl, guiding the formation of the more stable carbocation intermediate during the reaction.

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Textbook Question

What are the products of the following reactions, assuming that one equivalent of each reagent is used in each reaction?

Textbook Question

A student wanted to know whether the greater proximity of the nucleophile to the C-2 carbon in the transition state is what causes the 1,2-addition product to be formed faster when 1,3-butadiene reacts with HCl. Therefore, she decided to investigate the reaction of 2-methyl-1,3-cyclohexadiene with HCl. Her friend told her that she should use 1-methyl-1,3-cyclohexadiene instead. Should she follow her friend's advice?

Textbook Question

The experiment shown next and discussed in Section 8.13 shows that the proximity of the chloride ion to C-2 in the transition state causes the 1,2-addition product to form more rapidly than the 1,4-addition product.

a. Why was it important for the investigators to know that the preceding reaction was being carried out under kinetic control?

Textbook Question

Predict the products of the following reactions.

(e) buta-1,3-diene + bromine water

Textbook Question

Predict the products of the following reactions.

(f) hexa-1,3,5-triene + bromine in CCl₄

Textbook Question

The following diene gives the same product regardless of whether the reaction is run under conditions of kinetic (0 °C) or thermodynamic (100 °C) control. Predict the product and explain this observation.

Textbook Question

Would you expect the following nucleophiles to do 1,2- or 1,4-addition?

(g)

(h)

(i)

Textbook Question

What products would be obtained from the reaction of 1,3,5-hexatriene with one equivalent of HBr? Disregard stereoisomers.

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