5-8 2.0 g 110 mL = 0.20 g/mL ; 1 00 mm = 1 dm 5-9 + 1 .74° (0.20) ( 1 ) = + 8.7° for (+ )-glyceraldehyde 0.5 g I 10 mL = 0.05 g/mL ; 20 cm = 2 dm 5- 1 0 - 5.0° (0.05) (2) = -50° for (-)-epinephrine Measure using a solution of about one-fourth the concentration of the first. The value will be either + 45° or -45°, which gives the sign of the rotation. 5-1 1 Whether a sample is dextrorotatory (abbreviated "( +)" ) or levorotatory (abbreviated "( -)") is determined experimentally by a polarimeter. Except for the molecule glyceraldehyde, there is no direct, universal correlation between direction of optical rotation (( +) and (-)) and designation of configuration (R and S). In other words, one dextrorotatory compound might have R configuration while a different dextrorotatory compound might have S configuration. (a) Yes, both of these are determined experimentally: the (+) or (-) by the polarimeter and the smell by the nose. (b) No, R or S cannot be determined by either the polarimeter or the nose. (c) The drawings show that (+)-carvone from caraway has the
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