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

11. Radical Reactions

Calculating Radical Yields

Organic Chemistry

11. Radical Reactions

Calculating Radical Yields

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5:35 minutes

Problem 21

Textbook Question

Suppose a 2-halobutane was needed for a synthetic sequence. Starting your synthesis with butane, would it be best to put a chlorine or bromine at that position? Explain.

Verified step by step guidance

Identify the position on butane where the halogen will be added. In this case, we are looking to synthesize 2-halobutane, which means the halogen will be added to the second carbon in the butane chain.

Consider the reactivity and selectivity of halogens. Chlorine and bromine are both halogens that can be used in radical halogenation reactions, but they have different reactivity profiles. Chlorine is more reactive but less selective, while bromine is less reactive but more selective.

Evaluate the reaction conditions. Radical halogenation typically involves the use of heat or light to initiate the reaction. The choice of halogen will affect the reaction conditions needed to achieve the desired product.

Consider the selectivity of the halogenation process. Bromine, being more selective, is more likely to add to the secondary carbon (C-2) in butane, leading to a higher yield of 2-bromobutane compared to 2-chlorobutane, which might result in a mixture of products due to chlorine's lower selectivity.

Decide on the halogen based on the desired outcome. Given the need for a specific 2-halobutane, bromine would be the better choice due to its higher selectivity, which minimizes the formation of undesired isomers and maximizes the yield of the target compound.

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Key Concepts

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

Halogenation of Alkanes

Halogenation is a chemical reaction that involves the addition of halogens to alkanes, typically through a free radical mechanism. In the case of butane, halogenation can introduce a chlorine or bromine atom at a specific position, such as the 2-position, by using reagents like Cl2 or Br2 under UV light or heat. The choice of halogen affects the reactivity and selectivity of the reaction.

Reactivity of Halogens

Chlorine and bromine differ in their reactivity due to their atomic size and bond strength. Chlorine is more reactive than bromine, leading to faster reactions but potentially less selectivity. Bromine, being less reactive, can offer more controlled and selective halogenation, which is often preferred in synthetic sequences to minimize side reactions and improve yield.

Stability of Alkyl Halides

The stability of alkyl halides is influenced by the type of halogen and the position of substitution. Secondary alkyl halides, like 2-halobutane, are generally more stable than primary ones due to hyperconjugation and inductive effects. Bromine, forming weaker C-Br bonds compared to C-Cl, can result in more stable intermediates, which is advantageous in synthesis for subsequent reactions.

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Related Practice

Textbook Question

Suppose you intend to synthesize the secondary alkyl halide from each reaction shown.

(a) What is the atom economy of each reaction?

Textbook Question

Suppose you intend to synthesize the secondary alkyl halide from each reaction shown.

(b) What is the E-factor, effective mass yield, and process mass intensity?

Textbook Question

The deuterium kinetic isotope effect for the halogenation of an alkane is defined in the following equation, where X･ = Cl･ or Br･

Predict whether chlorination or bromination would have a greater deuterium kinetic isotope effect.

Textbook Question

Predict the product(s) of the following halogenation reactions. Only one equivalent of the halogen is used in each case. If the reaction proceeds selectively, indicate this by only drawing the major product. If the reaction is not selective, draw all possible products.

(b)

Textbook Question

At 600 °C, the ratio of the relative rates of formation of a tertiary, a secondary, and a primary radical by a chlorine radical is 2.6 : 2.1 : 1. Explain the change in the degree of regioselectivity compared to what was found in Problem 44.

Multiple Choice

What is the percentage yield of the major product?

Multiple Choice

What is the percentage yield of the major product?

Textbook Question

The chlorination of pentane gives a mixture of three monochlorinated products.

b. Predict the ratios in which these monochlorination products will be formed, remembering that a chlorine atom abstracts a secondary hydrogen about 4.5 times as fast as it abstracts a primary hydrogen.

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