15. If the equilibrium constant (K_eq) of a reaction is 0.5 then which of the following that must be true?
(A)The reaction will have an early transition state.
(B)Reaction equilibrium will favor the products.
(C) Gibbs free energy (G) is positive.
(D)Gibbs free energy (G) is negative.

11. The structure below is a potent analgesic agent (pain reliever) (J. Med. Chem., 2009, 5685). How many secondary carbons are in this structure?(A)2 (B)4 (C) 6(D)12

12. How many methylene groups are present in 2,4-dimethylhexane? (A)0 (B)1 (C) 2(D)6

13. Among the butane conformers, which occur at energy minima on a graph of potential energy versus dihedral angle? (A)gauche only (B)eclipsed and totally eclipsed (C) gauche and anti(D)eclipsed only

14. Which of the following species is not formed through a termination reaction in the chlorination of methane? (A)CH3Cl (B)HCl (C) H2(D)CH3CH3

16. Which is a measure of the randomness of a system? (A)entropy (B)enthalpy (C) free energy(D)halogenation

17. Which of the following statements correctly describes the contribution of ΔS° to ΔG° ? (A)The entropy term makes a greater contribution to ΔG° at low temperatures. (B)The entropy term makes a greater contribution to ΔG° at high temperatures. (C) The entropy term makes a greater contribution to ΔG° in exothermic reactions. (D) The entropy term makes a greater contribution to ΔG° in endothermic reactions.

18. Which of the following is true for the initiation step of a free radical chlorination reaction? (A)ΔH° ＞ 0 and ΔS° ＞ 0 (B)ΔH° ＞ 0 and ΔS° ＜ 0 (C) ΔH° ＜ 0 and ΔS° ＞ 0(D)ΔH° ＜ 0 and ΔS° ＜ 0

19. What term describes the structural relationship between cis-1,2-dimethylcyclopentane and trans-1,3-dimethylcyclopentane? (A)not isomers (B)constitutional isomers (C) enantiomers(D)diastereomers

20. What is the structural relationship between the two molecule shown below?(A)constitutional isomers (B)enantiomers (C) diastereomers(D)conformational isomers

21. How many asymmetric carbon atoms are present in the molecule shown?(A)0 (B)1 (C) 2(D)3