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prelab 5 - CHM 318L.03(W08 ORGANIC CHEMISTRY...

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CHM 318L.03 (W08) ORGANIC CHEMISTRY LAB (08W_CSCI_CHM318L.03) > QUIZZES > REVIEW ASSESSMENT: REDUCTION Review Assessment: Reduction Submitted 2/8/08 12:57 PM Name Reduction Status Completed Score 130 out of 130 points Instructions Question 1 10 out of 10 points Which of the following is produced when a ketone is reacted with hydride (after work- up)? Selected Answer: a secondary alcohol Feedback: Hydride is a nucleophilic hydrogen (H - ), which will attack an electrophilic carbonyl (C=O) to give an alcohol (C-OH). This is an example of a REDUCTION reaction, since we have lost a C-O bond and gained a C-H bond. Since the starting ketone has TWO alkyl groups, the product would be a secondary alcohol. An aldehyde would be reduced by hydride to a primary alcohol. Question 2 10 out of 10 points A chiral compound ____________. Selected Answer: all of the above Feedback: Since the starting ketone in our reaction has a chiral center and hydride addition generates a new chiral center, then the product obtained will be a mixture of diastereomers. We can use 1 H NMR to determine the relative amounts of each. Question 3 10 out of 10 points Which structure represents the most stable chair conformation of trans-2- methylcyclohexanol? Selected Answer: 2
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Feedback: Large groups prefer to be in the equatorial position so (2) is the most stable conformation with the least amount of sterics. There are more 1,3-diaxial interactions (sterics) in the diaxial chair conformation (1). Structures (3) and (4) represent cis-2-methylcyclohexanol, so their stability is irrelevant to this question. Question 4 10 out of 10 points How would you use an NMR spectrum to determine the ratio of isomeric products? Selected Answer: by integrating the sizes of the signals in the 1 H NMR Feedback: Integration of a hydrogen signal sets measures the area of the peak(s), and this area is proportional to the number of protons causing the particular signal. If you have twice as much isomer A as isomer B (i.e.,
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