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Compound X is a d-aldohexose that can adopt a b-pyranose
Chapter 24, Problem 24.86(choose chapter or problem)
Compound X is a d-aldohexose that can adopt a b-pyranose form with only one axial substituent. Compound X undergoes a Wohl degradation to produce an aldopentose, which is converted into an optically active alditol when treated with sodium borohydride. From the information presented, there are only two possible structures for compound X. Identify the two possibilities and then propose a chemical test that would allow you to distinguish between the two possibilities and thereby determine the structure of compound X.
Questions & Answers
QUESTION:
Compound X is a d-aldohexose that can adopt a b-pyranose form with only one axial substituent. Compound X undergoes a Wohl degradation to produce an aldopentose, which is converted into an optically active alditol when treated with sodium borohydride. From the information presented, there are only two possible structures for compound X. Identify the two possibilities and then propose a chemical test that would allow you to distinguish between the two possibilities and thereby determine the structure of compound X.
ANSWER:Step 1 of 2
In this exercise, we're told that compound X is a D-aldohexose that can adopt a -pyranose form with only one axial substituent. We’re also told that compound X undergoes a Wohl degradation to produce an aldopentose; treatment of this aldopentose with sodium borohydride gives an optically active alditol. Using all this information, we're asked to identify the possible structures for compound X. We‘re also asked to propose a chemical test that l would allow us to narrow the possibilities and determine the true structure of compound X.
From examining the complete set of D-aldohexoses in their -pyranose forms, we find that only two can adopt
orientation that contains just one axial substituent: D-mannose and D-galactose.
