Question

1.) The specific rotation, [?]_{D}, for
**sucrose** is +**67**. What is the
observed rotation for a solution of **0.70** g of
**sucrose** in 10 mL of water in a sample tube having
a pathlength of 10 cm?

___degrees .

2.) The observed rotation of a solution of **1.7**
g of a compound in 10 mL of water is +**13** degrees.
If the pathlength is 10 cm, what is the specific rotation of the
compound?

Answer #1

1) The relation between observed and specific rotation is as follows,

[?]_{l}^{T} = ? / lc

where [?]_{l}^{T} = specific rotation

? = observed rotation

l = Pathlength of sample tube in dm ( 10 cm = 1 dm)

c = conc. of solution in g per 100 mL

From the data provided we know that,

[?]_{l}^{T} = +67

l = 10 cm = 1 dm

c = 0.7 g in 10 mL = 7 gm in 100 mL

Plugging these values in the equation we get,

67 = ? / 1 x 7

=> **? = +469 degrees**

2) This is similar to the previous question. We again need to plug the values provided to get the unknown. Only this time the unknown is specific rotation

The data provided is,

? = +13

l = 10 cm = 1 dm

c = 1.7 g in 10 mL = 17 gm in 100 mL

=> **[?] _{l}^{T} = 13 / 1 x 17 = 0.764
degrees**

1) The specific rotation, [α]D, for
sucrose is +67. What is the
observed rotation for a solution of 0.50 g of
sucrose in 10 mL of water in a sample tube having
a pathlength of 10 cm? Answer in degrees.
2) The observed rotation of a solution of 1.3 g
of a compound in 10 mL of water is +11 degrees. If
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1a.) The specific rotation, [α]D, for
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of (-)-pseudoephedrine in 10 mL of water in a
sample tube having a pathlength of 10 cm?
The observed rotation of a solution of 0.75 g
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If the pathlength is 10 cm, what is the specific rotation of the
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1b.) The specific rotation, [α]D, for
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The specific rotation, [α]D, for
(-)-2-butanol is +14. What is the
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(-)-2-butanol in 10 mL of water in a sample tube
having a pathlength of 10 cm?
degrees .
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a compound in 10 mL of water is +5.8 degrees. If
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3.50 g of the mixture was dissolved in 10.0 mL of water. This
solution was then placed in a sample cell with a pathlength of 10.0
cm and the observed rotation was +0.70. Calculate the % ee of the
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content of their delivered beets. A sample is taken from each load
of beets and the sugar content in the beets is determined by
polarimetry of the beet extract. In a typical solution 50 grams of
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