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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6:56 minutes

Problem 28b

Textbook Question

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

Verified step by step guidance

Step 1: Analyze the structure of the starting compound. The molecule contains two double bonds, which are conjugated (alternating single and double bonds). This conjugation can influence the reactivity of the molecule.

Step 2: Identify the reagent used in the reaction. HBr (hydrobromic acid) is a strong acid and provides a source of Br⁻ ions. The reaction will proceed via electrophilic addition to one of the double bonds.

Step 3: Determine the regioselectivity of the reaction. According to Markovnikov's rule, the hydrogen atom from HBr will add to the carbon of the double bond that has more hydrogens, while the bromine atom will add to the carbon with fewer hydrogens.

Step 4: Consider the reaction mechanism. The reaction proceeds through the formation of a carbocation intermediate. The stability of the carbocation will determine which double bond reacts. A more stable carbocation (e.g., tertiary > secondary > primary) will be favored.

Step 5: Predict the product. After the addition of HBr to the most reactive double bond, the bromine atom will be attached to the carbon with fewer hydrogens, and the hydrogen atom will be attached to the carbon with more hydrogens. The remaining double bond will stay intact.

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Key Concepts

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

Hydrohalogenation

Hydrohalogenation is a chemical reaction where an alkene reacts with a hydrogen halide (like HBr) to form an alkyl halide. The reaction typically follows Markovnikov's rule, where the hydrogen atom from the hydrogen halide adds to the carbon with the most hydrogen substituents, leading to the more stable carbocation intermediate. This process is crucial for understanding how alkenes can be transformed into more functionalized products.

Markovnikov's Rule

Markovnikov's rule states that in the addition of HX (where X is a halogen) to an asymmetric alkene, the hydrogen atom will attach to the carbon with the greater number of hydrogen atoms already attached. This results in the formation of the more stable carbocation intermediate, which influences the final product distribution. Understanding this rule is essential for predicting the outcome of hydrohalogenation reactions.

Carbocation Stability

Carbocation stability is a key concept in organic chemistry that refers to the relative stability of positively charged carbon species. Carbocations are stabilized by alkyl groups through hyperconjugation and inductive effects, with tertiary carbocations being the most stable, followed by secondary and primary. The stability of the carbocation formed during hydrohalogenation directly affects the regioselectivity of the reaction and the final product.

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Related Practice

Textbook Question

Draw the products obtained from the reaction of one equivalent of HBr with one equivalent of 1,3,5-hexatriene.

a. Which product(s) will predominate if the reaction is under kinetic control?

b. Which product(s) will predominate if the reaction is under thermodynamic control?

Textbook Question

a. How could each of the following compounds be prepared from a hydrocarbon in a single step?

b. What other organic compound would be obtained from each synthesis?

Textbook Question

What are the major 1,2- and 1,4-addition products of the following reaction? Indicate the kinetic and the thermodynamic products.

Textbook Question

What are the major 1,2- and 1,4-addition products of the following reaction? Indicate the kinetic and the thermodynamic products.

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.

(b) cyclopentadiene + anhydrous HCl

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