Organic Chemistry: Concepts and Applications - Headley Allan D. 2020

Addition Reactions Involving Alkenes and Alkynes
End of Chapter Problems

1. 8.19 Give the major organic product for the reaction of 3-methyl-2-pentene with each of the following reagents:

2. 8.20 Give a mechanism to explain the reaction shown below:

3. 8.21 Give the products for each of the following addition reactions.

4. 8.22 Give the reactant for each of the following addition reactions.

5. 8.23 Complete the following reactions by giving the structures of the reactant, missing reagents, or major organic product. Include appropriate stereochemistry in the products where applicable.

6. 8.24 Provide the reagent(s) necessary to carry out that lettered transformation.

7. 8.25 Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the product shown for the reaction below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism (hint: note that there are two alkene groups, which means two nucleophiles present in the molecule).

8. 8.26 Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the product shown for the reactions below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism(hint: note that there are two alkene groups, which means two nucleophiles present in the molecule).

9. 8.27 The following cyclization was observed when trying to carry out an addition of Br₂ to the unsaturated compound shown below. Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the products shown for the reaction below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism.

10. 8.28 The following cyclization was observed when trying to carry out an addition of Br₂ to the unsaturated compound shown below. Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the unexpected product shown for the reaction below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism (hint: the first step in the mechanism is given).

11. 8.29 The routine addition of HCl across the double bond of a vinylcyclohexane gave a small amount of an unexpected rearranged product. Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the product shown for the reaction below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism.

12. 8.30 Rearrangement of carbocation intermediates often occurs for addition reactions. With this information in mind, explain by appropriate mechanisms (i.e. step-by-step descriptions and curved arrows to indicate electron movements) the formation of the organic product shown for the following reaction (hint: the first step in the mechanism is shown).

13. 8.31 The following cyclization was observed in the oxymercuration—demercuration of the unsaturated compound shown below. Provide a reasonable mechanism to explain the formation of the products shown.

14. 8.32 Explain by an appropriate mechanism (i.e. step-by-step descriptions and curved arrows to indicate electron movements) the formation of the organic product shown for the following reaction (hint: the first step in the mechanism is shown).

15. 8.33 Using arrows to indicate electron movement, give a step-by-step description of a mechanism to explain the reaction shown below. Clearly show the structures of all intermediates, along with the appropriate formal charge in your mechanism.

16. 8.34 Determine an appropriate starting alkene and reaction conditions for the synthesis of the compounds shown below.

17. 8.35 Give the structures for the molecules missing in the sequence of reactions shown below. The reagents used to carry out each transformation are represented by numbers and are shown below the reaction scheme.

1. Br₂/CCl₄; 2. HBr, peroxides; 3. Br₂/H₂O; 4. HBr (no peroxides); 5. (i) BH₃, (ii) H₂O₂, OH⁻; 6. (i) Hg(OAc)₂/H₂O, (ii) NaBH₄; 7. H₂/Pd.

18. 8.36 For the reaction scheme shown below, provide the reagent(s) necessary to carry out each lettered transformation: (Note: some transformations may require more than one step and these steps must be indicated clearly).

19. 8.37 Supply the necessary reagents and reaction conditions to complete the reaction scheme shown below.

20. 8.38 The routine addition of HBr across the double bond of the compound shown below gave an unexpected rearranged compound as one of the products. Propose a step-by-step mechanism for the formation of this product.

21. 8.39 Due to the presence of pi (π) bonds, alkenes are nucleophilic. With this information in mind, propose a step-by-step mechanism using curved arrows to indicate electron movements for the reaction shown below (hint: in the first step a carbocation is formed, which is attacked by the other nucleophilic double bond to form a ring before being attacked by the bromide anion).

22. 8.40 Show how to accomplish the following transformations (synthesis). All reagents, reaction conditions, and appropriate solvents must be clearly shown.

23. 8.41 For the addition of HBr to 2-methylpropene, the major product that was isolated is 2-bromo-2-methylpropane, and only a trace of 1-bromo-2-methylpropane obtained. On the other hand, for the same addition reaction, but in the presence of peroxide and heat, the major product is 1-bromo-2-methylpropane and the minor product is 2-bromo-2-methylpropane. Write appropriate mechanisms to explain the formation of both products under the two different reaction conditions, i.e. no peroxide and with peroxide and heat, respectively (hint: peroxides (ROOR) readily dissociate to form radicals).