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Which of the following statements regarding the structural relationships of carbohydrates is INCORRECT?

Options

  1. A-D-glucopyranose and -D-glucopyranose are anomers differing in configuration at C-1.
  2. BD-glucose and D-mannose are epimers differing in configuration at C-4.
  3. CD-glucose and D-fructose are functional isomers.
  4. DD-glucose and D-galactose are epimers differing in configuration at C-4.

Correct answer

B. D-glucose and D-mannose are epimers differing in configuration at C-4.

Step-by-step solution

Let us evaluate each statement: Statement 1: -D-glucopyranose and -D-glucopyranose differ only in the configuration at the anomeric carbon (C-1). They are indeed anomers. This statement is correct. Statement 2: D-glucose and D-mannose are diastereomers that differ in configuration at exactly one stereocenter. However, they differ at C-2, not C-4. Therefore, they are C-2 epimers. This statement is incorrect. Statement 3: D-glucose is an aldohexose (contains an aldehyde group) and D-fructose is a ketohexose (contains

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