Do any nine problems.

1. One compound in each of the following pairs is more reactive than the other under the specified conditions. Indicate which one is more reactive, and explain why in just a few words:

   

   

   

   

   

2. Carey and Sundberg, Problem 4.2.

3. Carey and Sundberg, Problem 4.4.

4. Carey and Sundberg, Problem 4.9

5. Carey and Sundberg, Problem 4.17.

6. Explain the following observations:
   • The reactivity of M⁺ X^- toward n-butyl brosylate in acetone is: chloride most reactive, iodide least when M⁺ is Bu₄N⁺, but the reverse when M⁺ is Li⁺

   • Fluoride is more reactive than bromide toward n-butyl brosylate when the solvent is dimethylsulfoxide, but less reactive when the solvent is water.

   • The compounds shown below racemize during solvolysis in aqueous dioxan; they also undergo ¹⁸O equilibration. (That is, if starting material is isolated before it is all consumed, it is found to be partly racemic; the O label is found in both oxygens.)
     

     For isomer A, the rates of racemization and of ¹⁸O equilibration are the same; for B, equilibration is faster than racemization. Propose a mechanism that explains these differences.

   • The attempted elimination of trimethyl amine takes different courses depending on stereochemistry:
     

7. Explain the following observations:

   • The ¹H nmr spectrum of 2,6-dimethyl-2-heptyl carbocation in superacid medium at -100^o shows a single peak for all four methyl groups.

   • When the t-butyl carbocation labeled at the 3^o carbon with ¹³C is heated in superacid at 70^o, complete scrambling of the label is observed. Suggest a mechanism.

   • The relative rates of solvolysis in buffered acetic acid of the compounds H₂NCH₂CR₂CH₂CH₂Br vary with the structure of R as follows: R = H, 1.0; R = Me, 158, R = Et, 594; R = iPr, 9190. Explain.

   • A single product is obtained from cis-9-chlorodecalin upon treatment with EtO^-/EtOH, whereas the trans- isomer gives two products.

8. Use orbital interaction theory to describe the bonding in the bridged ethyl carbocation.

9. Carey and Sundberg, Problem 5.1

10. Carey and Sundberg, Problem 5.2.

11. Carey and Sundberg, Problem 5.14.

12. Write mechanisms for the following reactions:
    

13. The compounds shown below, having R = H or R = CH₃, are solvolyzed in aqueous ethanol. The ratio of rates for R = CH₃ compared to R = H is shown below each structure. Explain the variaation.