115年 - [無官方正解]115 國立臺灣大學_ 碩士班招生考試試題：有機化學(A)#137731

1. Chain-growth polymerization proceeds by which of the following mechanisms?(A) radical polymerization (B) cationic polymerization (C) anionic polymerization(D) A and В (E) A, B, and C

2. Identify the following compounds as R or S.
(A) S, S, R (B) S, R, S (C) R, S, S (D) S, S, S (E) R, R, R

3.What is the carbon nucleophile which attacks molecular bromine in the acid-catalyzed a-bromination of a ketone?(A) an enolate(D) a carbocation(B) a Grignard reagent (C) an acetylide
(E) an enol

4. In nucleophilic acyl substitution(A) protonation of the carbonyl is followed immediately by loss of the leaving group.(B) loss of the leaving group is followed by rearrangement of the carbocation.(C) addition to the carbonyl by a nucleophile is followed by loss ofthe leaving group.(D) ester hydrolysis is followed by deprotonation.
(E) an S_N2 reaction occurs.

5. Dicyclohexylcarbodiimide (DCC) is used(A) to determine the N-terminal amino acid of a peptide.(B) to sequence amino acids in a peptide.(C) to detect amino acids derived from hydrolysis of a peptide.(D) to couple amino acids during solid-phase peptide synthesis.
(E) to hydrolyze peptides on the carboxyl side of aromatic amino acid residues.

6. What type of intermediate is present in the SN2 reaction of cyanide with bromoethane?(A) carbocation(D) carbanion(B) free radical (C) carbene
(E) This reaction has no intermediate.

7. Predict the specific rotation of the compound shown.
(A) It is impossible to predict; it must be determined experimentally.(B) Because both asymmetric centers are R, the compound is dextrorotatory.(C) Because both asymmetric centers are S, the compound is dextrorotatory.(D) Zero; the compound is achiral.
(E) Because this compound represents a racemic mixture, the compound is dextrorotatory.

8. Which molecule below has a significant band in the 1720-1780 cm^-1 range of its IR spectrum? (A) CH₃CH₂CH₂OH (B) CH₃C=CCH₂CH₃ (C) CH₃CH₂CH(NH₂)CH₃ (D) (CH₃)₃N(E) CH₃CO₂CH2CH₃

9. Which of the compounds below undergoes solvolysis in aqueous ethanol most rapidly?(A) 3-iodo-3-methylpentane (B) methyl iodide (C) isopropyl chloride(D) 3-chloropentane(E) cyclohexyl bromide

10. Which of the following statements best describes what vulcanization means? (A) a process by which rigid and non-sticky rubber can be made soft and sticky. (B) the heating of rubber with sulfur. (C) a chemical process discovered by Charles Schultz in 1944. (D) a chemical process that destroys cross-linking in rubber. (E) a chain transfer reaction.

11. How many distinct monochlorinated products, including all stereoisomers, can result when methylcyclobutane is heated in the presence of Cl₂? (A) 2 (B) 6(C) 5 (D) 4(E) 3

12.What is the major organic product obtained from the following reaction?
(A) I(B) II (C) III (D) IV (E) V

13. When CH₃CH₂CHO reacts with PhNHNH₂ under conditions of acid catalysis, the major organic product is_______.(A) a nitrile (B) an imine(C) a hydrazone(D) an oxime (E) a ketone

14. What compound results from the 1,4-addition of one equivalent of HBr to 1,3-butadiene?(A) 1-bromo-1-butene(B) 1-bromo-2-butene(C) 4-bromo-1-butene(D) 3-bromo-1-butene(E) 2-bromo-2-butene

15. Which of the following is aromatic?(A) cycloheptatrienyl cation (B) 1,3,5-hexatriene(C) cyclobutenyl anion(D) 1,3-cyclohexadiene(E) cyclopentadienyl cation

16.How many hydrogens in the structure of 2,3-dimethylcyclopentanone are replaced by deuteriums when it is shaken in D₂O containing trace hydroxide?(A) 1 (B) 2 (C) 3 (D) 6 (E) 7

17. Consider molecules with the formula C₁₀H₁₄Br₂O₂. Which of the following structural features is possible within this set of
molecules?(A) 3 triple bonds(D) 4 double bonds(B) 2 rings and 1 double bond
(E) 3 rings and 2 double bonds(C) 2 rings and 1 triple bond

18. Predict the two most likely mechanisms for the reaction of 2-iodohexane with sodium ethoxide.(A)S_N2 and S_N1 (B) E1 and E2 (C) S_N2 and E2(D) E1 and S_N1 (E) E2 and S_N1

19. When 1,3-butadiene reacts with CH₂=CHCN, which of the terms below best describes the product mixture?(A) a mixture of two diastereomers(C) a racemic mixture
(E) a mixture of bicyclic compounds(B) a single compound(D) optically active

20. Give the product for the following reaction.
(A) alanine(B) leucine (C) valine(D) isoleucine(E) glycine

21. Which of the following statements correctly describes the contribution of △S° to△G°?(A) The entropy term makes a greater contribution to AG° at high temperatures.(B) The entropy term makes a greater contribution to AG° at low temperatures.(C) The entropy term makes a greater contribution to AG° in exothermic reactions.(D) The entropy term makes a greater contribution to AG° in endothermic reactions.
(E) The entropy term always makes a more significant contribution to AG° than does the enthalpy term.

22. What compound is produced when N,N-dimethylpropanamide is treated with LiAlH4?(A) CH₃CH₂CONH₂ (B) CH₃CH₂CH₂NH₂(C) CH₃CH₂CH₂OH(D) CH₃CH₂CH₂N(CH₃)₂ (E) CH₃CH₂N(CH₃)₂

23. Which ofthe following is a vicinal dihalide?(A) cis-1,2-dibromocyclopentane(B) 3,3-dichloropentane(C) trans-1,4-diiodocyclohexane(D) isobutyl chloride
(E) 1,3-dibromoheptane

24. Reduction of a 2-ketohexose with NaBH4 yields:(A) a single aldohexose (B) a mixture of acetals (C) a mixture of alditols(D) a mixture of pyranoses (E) a mixture of cyclic hemiacetals

25. When the 1,7-diester CH₃O₂CCH₂CH₂CH(CH₃)CH₂CH₂CO₂CH₃ is treated with sodium methoxide and the reaction mixture is
subsequently neutralized with acid, what kind of compound is the major organic product?(A) a cyclic ẞ-diketone (B) a cyclic ẞ-ketoester (C) an acyclic ẞ-diester(D) an acyclic ẞ-ketoacid (E) a cyclic ẞ-diketone

26. When thiols form disulfide bonds, the reaction can be described as_____.(A) elimination(B) sulfation(C) sulfonation(D) oxidation(E) reduction

27. Which of the following compounds will not undergo Friedel-Crafts acylation when treated with CH₃CH₂COC1, AlCl₃?(A) toluene (B) p-xylene (C) anisole (D) benzophenone (E) ethoxybenzene

28. What is the major product when (CH3)2CHCH2CH,Br is subjected to the following reaction sequence: (i) Mg, (ii) CO₂, (iii) H₃O⁺?(A) 3-methyl-1-butanol (B) 2-methyl-2-butanol (C) 4-methyl-1-pentanol(D) 4-methylpentanoic acid (E) 3-methylbutanoic acid

29. If a signal is observed in the 170 to 200 ppm range in a C-13 NMR spectrum, what is the most likely type of functional group associated with that carbon atom? (A) carbonyl carbon(B) allylic carbon (C) aromatic carbon (D) carbon/carbon triple bond(E) carbon/carbon double bond

30.Which ofthe following reagents is used in the following reaction?
(A) Cl₂/CCI₄ (B) HCI (C) Cl₂/hv (D) HCIO₄ (E) PC1₅

1. Which would you expect to undergo E2 elimination faster, trans-1-bromo-4-tert-butylcyclohexane or cis-1-bromo-4-tertbutylcyclohexane? Draw each molecule in its more stable chair conformation, and explain your answers. (10 points)

2.Electrophilic aromatic substitution reactions of pyridine normally occur at C3. Draw the carbocation intermediates resulting from reaction of an electrophile at C2, C3, and C4, and explain the observed result. (14 points)

(a) Please draw two key resonance structures of diazomethane. (8 points)

(b) Use curved arrows to describe the detailed mechanism of these two steps. (8 points)