27. In the following four stereoisomers of 2-amino-3-hydroxybutanoic acid which chiral carbons have 2R,3S configuration?

23. What final product would be obtained from following reaction??

24. Which statements describe the bonding in the water molecule?  1. polar covalent  2. π bond  3. sp3 hybridization(A) 1 only (B) 1 and 2 only (C) 1 and 3 only (D) 2 and 3 only

25. In the following SN2 reaction which one would be predicted to be the fastest? (A) H2O + CH3Br → HOCH3 + HBr(B) OH- + CH3Br→ HOCH3 + Br-(C) H2S + CH3Br→  HSCH3 + HBr (D)SH- + CH3Br → HSCH3 + Br

26. Bis(2-ethylhexyl)phthalate, commonly abbreviated DEHP, is an organic compound with the formula C6H4(C8H17COO)2. It is sometimes called dioctyl phthalate and abbreviated DOP. Being produced on a massive scale by many companies, it has acquired many names and acronyms, including BEHP and di-2-ethylhexyl phthalate. Recently, the illegal use of the plasticizer DEHP in clouding agents for use in food has been reported in Taiwan, what is the structure of DEHP?

28. The volume-temperature plots below were made at different values of constant pressure while the number of moles of gas in each experiment remained the same. Which curve represents measurements at highest pressure? (A) A (B) B (C) C (D) D

29. Consider the following changes: H2O(s) → H2O(l)  △ H1 H2O(l) → H2O(g)  △ H2 H2O(g) → H2O(s)  △ H3 Using Hess’ Law, the sum all of △ H1 + △ H2 + △ H3 is  (A) > 0 (B) = 0 (C) < 0 (D) sometimes > 0 and sometimes < 0

30. Choose the best series of reactions (A-D) for the synthesis of 3-bromoanilline from benzene shown below.

31. Which of the following orbital diagrams represents a paramagnetic atom? (A) 1 and 2 only (B) 1 and 3 only (C) 2 and 3 only (D) 3 only

32. In a certain mountain range, the atmospheric pressure is 608 mmHg. What is the temperature of water boil under these conditions? Some information that may be useful is the following: ,R=8.314 KJ/(K.mol); △ Hvap=44.0kJ/mol (A) 94.2 ℃ (B) 96.3 ℃ (C) 98.4 ℃ (D) 99.6 ℃ (E)一律送分

33. When U collides with one neutron, fission occurs, and the products are four neutrons, Sr , and