Question

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A. Which of the following Newman projections would represent the least stable conformer of 2,2,3.3-tetramethylbutane, looking down the 2,3 bond? H3C H3C H3C H3C CH3 b) CH3 H3C e) a) c) CH3 H3C CH3 CH CH3 CH о он B. which one of the following compounds would be chiral? Br он о он a) но HO O он HO C C. which of the following could potentially be used to distinguish between enantiomers? b) NMR c) your nose d) GC-MS e) UV a) IR D. A mixture of two enantiomers is resolved and the rotation of each isolated sample is observed. Enantiomer A is found to have a rotation of +15 and enantiomer B is found to have a rotation of -5°. From these measurements it can be concluded that: a) Enantiomer A must be R b) Enantiomer B must be S c) Enantiomer A was resolved with higher optical purity d) The enantiomers were both completely resolved e) None of the above statements (a-d) are correct D. A mixture of two enantiomers is resolved and the rotation of each isolated sample is observed. Enantiomer A is found to have a rotation of +150 and enantiomer B is found to have a rotation of -50. From these measurements it can be concluded that: a) Enantiomer A must be R b) Enantiomer B must be S c) Enantiomer A was resolved with higher optical purity d) The enantiomers were both completely resolved e) None of the above statements (a-d) are correct. 2. (3 points total) Identify each of the following pairs as enantiomers, diastereomers, or identical molecules. Show priority assignments (where applicable) to receive partial credit. Si CF3 Si CF3 a. H3C OH CHO но о b. CH2OH но H3C CH3 На HOH,C 3. (5 points total) The structure of B-D glucopyranose (a form of glucose) consists of a 6-membered cyclic ring containing an O. Chair conformations for this ring can be drawn as for cyclohexane, in which the oxygen in the ring is treated similarly to a CH2 group in a chair cyclohexane он HO он A. (1.25 points) in β-D glucose. Assign absolute configuration to all the chiral centers B-D-glucose B. (1.25 points) Fill in the appropriate substituents on the chair framework provided below to draw B-D glucose. a diastereomer. Be sure not to draw its enantiomer or C. (1.25 points) Next to the structure you drew in part B, draw its ring flipped conformer. D. (1.25 points) Identify the more stable of the two conformers of β-d glucose you drew in part B; briefly explain.

Answer 1

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