1. Which of the following are chiral? Which are achiral?
a) 2-bromopentane; b) 3-bromopentane; c) 1-bromo-2-methylbutane; d)
2-bromo-2-methylbutane
2. Identify the chiral centers, if any, in
| a)
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b)
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| c)
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d)
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3. Draw the structure of all the isomers of 2-butene and all the possible planes of symmetry.
4. An aqueous solution containing 10.0 g of optically pure fructose was diluted to 500. mL with water and placed in a 20.0 cm long polarimeter tube. The measured optical rotation was -5.20°. Calculate the specific rotation of fructose.
5. Convert the following into Fischer projection formulas.
a)
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b)
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6. Identify each of the following fischer projections as either D- or L-glyceraldehyde.
a)
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b)
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c)
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7. Write all the fischer projections of all the possible stereoisomers of the following compound and identify the pairs of eneatiomers.
8. Explain why the following stereoisomer of 2,4-pentanediol is achiral despite the fact that it contains two chiral carbons.
9. Classify each of the following monosaccharides as D or L.
a)
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b)
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10. For the carbohydrates diagrammed in question #9 draw the Haworth projection formulas of both the furanose and pyranose form.
Answer Set for Chem 110.00 Problem Set#4:
1.a) chiral; b) achiral; c) chiral; d) achiral
2.
a)
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b)
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| c) No chiral centers thus achiral. | d)
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3. For both the cis and trans isomers the molecular plane is a plane of symmetry. For the cis isomer a plane of symmetry also exists perpendicular to the molecular plane and passes directly through the carbon-carbon double bond.
4. [a]D = -130°
5.
a)
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b)
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6.a) D, b) L, c) D
7. The pair of stereoisomers that are enantiomers are: 1 and 2, 3 and 4, 5 and 6, and 7 and 8.
8. The stereoisomer depicted in the fischer projection of 2,4-pentanediol is achiral even though it contains two chiral carbons because the chiral carbons are equivalent and the stereoisomer contains a plane of symmetry. The stereoisomer depicted is an example of a meso compound.
9.a) d-arabinose; b) d-fructose
10.
| a) Furanose ring formation:
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| Pyranose ring formation:
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b) Furanose ring formation:
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| Pyranose ring formation:
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