13. Indicate which configuration is represented at the stereogenic center in ibuprofen. . R b. S . d. Z CH3 ( )-ibuprofen 14. A mixture that is 75% (R)-limonene and 25% (S)-limonene rotates plane-polarized light (i.e. is optically active). a. The statement is true b. The statement is false because the mixture is not racemic c. The statement is false because limonene is not chiral (achiral) limonene 15. Which 'H NMR data (in 8 ppm) are consistent with the structure shown? a. 7.9 (2H, d), 7.2 (2H, d), 4.4 (2H, q), 2.4 (3H, s), 1.4 (3H, t) b. 7.3 (4H, m), 4.1 (2H, q), 3.5 (3H, s), 1.2 (3H, t) c. 7.1 (1H, dt), 6.1 (1H, d); 2.4 (4H, m); 2.1 (2H, m) OCH,CH, H,C 16. A molecule has 3 chiral centers and no symmetry. Switching the configuration around two of the chiral centers generates aln a. enantiomer b. diastereomer c. constitutional isomer of the first structure.