Chem 210-1 F06 Ex2 p04

Chem 210-1 F06 Ex2 p04 - is measured and each gives a...

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5. "Tartaric acid" is the common name given to any of the straight-chain four carbon dicarboxylic acids with hydroxyl substituents at the middle two carbons. "L-tartaric acid" is the form of tartaric acid which has the specific structure shown on the right. It occurs in the juice of fermented grapes; it has a value for [ α] οφ+ 11.98 ο ατ25 ο Χ . H OH CO 2 H HO H HO 2 C a) The "L" in "L-tartaric acid" is used to specify (by comparison to L-glyceraldehyde) its absolute configuration in 3-dimensional space. Provide the absolute configuration of the chiral carbons in l-tartaric acid using the Cahn-Ingold-Prelog (or R/S) system. (5 points) c) Imagine you have three beakers (beakers X, Y, and Z), each containing an aqueous solution of tartaric acid and tartaric acid only. The optical rotation of each solution
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Unformatted text preview: is measured, and each gives a reading of zero. i) How could you determine for sure that the value for a was 0 o , not +360 o or -360 o ? (4 points) ii) Although each beaker contains only aqueous tartaric acid, beaker 'X' contains solute molecules of only o n e molecular structure; beaker 'Y' contains solute molecules of t w o molecular structures; and beaker 'Z' contains solute molecules with t h r e e distinct molecular structures. Indicate (using structures or unambiguous names) the molecular species in solution in each beaker. (6 points) b) If you took 10.0 mL of a solution containing 1 gram of L-tartaric acid, and placed it in a 2 dm tube, what value would you observe for a, the optical rotation? (3 points)...
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