Exp 9 - optical rotation study gives a result of a = 140o Suggest a dilution experiment to test whether the result is indeed 140 o and not 220o Ans

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EXP 9 Answers to Pre-lab Questions Questions 1-4, page 174 in "Techniques. ." 1. A sample of 2- butanol shows an optical rotation of +3.25 o. Determine the % ee and the molecular composition of this sample. The optical rotation of pure (+)-2-butanol is +13.0o. Ans. +3.25o x 100 % = 25.0 % ee detrorotatory or (+) +13.0o Molecular composition: 100 + 25 2 = 62.5 % dextrotoratory or (+) 37.5 % levorotatory or (-) 51LA W07 TA Note 19 or 100-25 = 2 37.5 % of (+) and (-) to make the racemic mixture that gives 0o optical activity reading. Therefore, (+) enantiomer of 2-butanol is 37.5 + 25.0 = 62.5 % is (+) enatiomer and 37.5 % is (-) enantiomer. 2. A sample of 2-butanol (See question 1) shows an optical rotation of 9.75o. Determine the % ee and the molecular composition of this sample. %ee: -9.75o -13.0o Molecular composition: 100+ 75 2 = 87.5 % levorotatory or (-) 12.5 %dextrotoratory or (+) Ans. x 100 % = 75.0 % ee levorotatory or (-) 3. An
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Unformatted text preview: optical rotation study gives a result of a = +140o. Suggest a dilution experiment to test whether the result is indeed +140 o and not 220o. Ans. If the concentration of the sample solution were halved, the rotation would either be +70o or 290o if the =140 o reading is originally correct. If 220 o were correct reading, the new reading would be 110 o or +250 o. Pre-Lab Question Question 1, p 46 in "Techniques. ." 1. (R)-(+)-limonene has a boiling point of 176oC. What made it possible to steam distill it at 100oC? Ans. Because the limonene is not miscible with water, the vapor pressures of limonene and water add together. When the combined pressure equals the atmospheric pressure, distillation occurs. The distillate contains limonene and water in proportion to their vapor pressures at the boiling point 51LA W07 TA Note...
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This note was uploaded on 02/25/2010 for the course CHEM 51LB 40639 taught by Professor Link during the Spring '10 term at UC Irvine.

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