Practice Test 2 - Organic Chemistry 1

20 questions. Answer them in any order, then submit to see your score and every explanation.

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1. The reaction of 1-hexene with $Hg(OAc)_2/H_2O$ followed by $NaBH_4$ gives 2-hexanol as the major product. How does this differ mechanistically from direct acid-catalyzed hydration, and what advantage does it provide?
2. For which of the following transformations would hydroboration-oxidation be an unsuitable method to achieve the desired product as the major product?
3. In the presence of a catalytic amount of sulfuric acid, 2-methylpropene reacts with methanol. What is the major organic product?
4. Treatment of 1-bromo-3-chloropropane with one equivalent of sodium hydrosulfide (NaSH) in DMSO primarily yields 3-bromopropanethiol. Which statement best explains this regioselectivity?
5. A student attempts to reduce 2-hexyne using catalytic hydrogenation. Instead of the expected alkene, the major product isolated is hexane. Which of the following reagent conditions was most likely used?
6. When (2,2-dimethylpropyl)amine is treated with NaNO2 and HCl, it undergoes a reaction that ultimately produces a rearranged alcohol. This transformation proceeds via a diazonium ion which decomposes to form a primary carbocation. Which species is the key intermediate immediately following this initial carbocation formation?
7. During the catalytic hydrogenation of an alkene, deuterium gas (D₂) is used instead of H₂ to study the mechanism. Analysis shows that both deuterium atoms end up on the same face of the original double bond in the product. However, when the reaction is performed in D₂O solvent instead of an aprotic solvent, some products show deuterium incorporation from the solvent as well. What mechanistic information do these observations provide?
8. What is the total number of unique stereoisomers for 2,4-dibromopentane?
9. In the radical addition of HBr to an alkene initiated by benzoyl peroxide, which species is generated during the initiation phase and then directly adds to the alkene π-bond in the first propagation step?
10. An internal alkyne is subjected to dissolving metal reduction using Na in liquid NH₃. Which of the following statements best describes the product and the mechanism?
11. Which sequence of reagents would best accomplish the conversion of 1-pentyne to 2-pentanol?
12. The substitution of the -OH group in an alcohol requires acid catalysis to convert it into a good leaving group (-OH₂⁺). In contrast, the substitution of the -SH group in a thiol often proceeds without a catalyst. What is the best explanation for this difference?
13. Despite containing highly polar C-Cl bonds, carbon tetrachloride (CCl₄) is a nonpolar molecule. Which of the following molecules is also nonpolar for the same reason?
14. Acid-catalyzed hydration (H₃O⁺) of 1-vinylcyclobutane leads to a rearranged alcohol as the major product. What is the structure of this product?
15. The addition of Br₂ to alkenes is stereospecifically anti. Which statement provides the best mechanistic explanation for this observation?
16. A student intends to prepare (Z)-2-butene from 2-butyne. They set up the reaction with 2-butyne, H₂ gas, and a standard Pd-C catalyst. They allow the reaction to run for an extended period with excess hydrogen. What is the most likely major product they will isolate?
17. A researcher wants to synthesize (R)-2-butanol using hydroboration-oxidation. Starting with an appropriate butene isomer, what additional consideration is necessary to obtain the desired enantiomer?
18. The reaction of (R)-1-bromo-1-phenylpropane with sodium methoxide in methanol produces an alkene. Which statement accurately describes the major product and the mechanism?
19. Consider the hydration of 3,3-dimethyl-1-butene using dilute $H_2SO_4$. What is the major product, and what key mechanistic feature explains this outcome?
20. While (E)-cyclooctene is a stable, isolable molecule, (E)-cyclohexene is extremely unstable and has only been observed transiently at low temperatures. What is the primary source of instability in (E)-cyclohexene?

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