15. Which sequence correctly ranks the following dienes in order of increasing reactivity in the Diels-Alder reaction? 
(A) 3 < 2 < 1
(B) 2 < 3 < 1
(C) 2 < 1 < 3
(D) 1 < 3 < 2
(E) 1 < 2 < 3 .

11. A pure sample of (S)-phenylalanine has a specific rotation of +70o . A mixture of the two enantiomers of phenylalanine gives a specific rotation of -7.0o . What are the percentages of the S and R enantiomers in the mixture? (A) 75 % S, 25 % R (B) 65 % S, 35 % R (C) 55 % S, 45 % R (D) 45 % S, 55 % R (E) 35 % S, 65 % R

12. Predict the major product when pyridine is treated with a mixture of nitric acid and sulfuric acid (A) 2-nitropyridine (B) 3-nitropyridine (C) 4-nitropyridine (D) 2,3-dinitropyridine (E) 2,4-dinitropyridine

13. Predict the product(s) for the following reaction.Diethylheptanedioate ?(A) I (B) II (C) III (D) IV (E) V

14. Which molecular formula is consistent with the following mass spectrum data?   at m/z= 84, relative height=10.0%  at m/z= 85, relative height=0.56% (A) C5H10O (B) C5H8O (C) C5H24 (D) C6H12 (E) C4H6O2

16. Rank the following compounds in increasing order of reactivity in the intramolecular displacement of p-bromophenolate to form a cyclic anhydride. (A) A < B < C (B) B < A < C (C) C < A < B (D) B < C < A (E) None of above

17. Which of the following undergoes solvolysis in water more rapidly?   (A) I (B) II (C) III (D) I and II (E) all of the above

18. Grignard reagents react with oxirane (ethylene oxide) to form 1o -alcohols but can be prepared in tetrahydrofuran solvent. Why is this difference in behavior observed? (A) Steric hindrance in the case of tetrahydrofuran precludes reaction with the Grignard. (B) There is a better leaving group in the oxirane molecule. (C) The oxirane ring is the more highly strained. (D) It is easier to obtain tetrahydrofuran in anhydrous condition. (E) Oxirane is a cyclic ether, while tetrahydrofuran is a hydrocarbon.

19. The regioselectivity and stereospecificity in the oxymercuration-demercuration of an alkene is best described as: (A) Markovnikov orientation with syn-addition (B) Markovnikov orientation with anti-addition (C) anti-Markovnikov orientation with syn-addition (D) anti-Markovnikov orientation with anti-addition (E)Markonikov orientation with both syn- and anti-addition

20. What is the major product of the following reaction?(A)(B)(C)(D)(E) None of the above.

21. What is the major product of the following reaction?  (A) I (B) II (C) III (D) IV (E) V