Question

Without referring to the chapter, draw the chair conformations of(c) β-D-galactopyranose (the C4 epimer of glucose).

Accepted Answer

Understand the structure of β-D-galactopyranose: It is a six-membered cyclic sugar (pyranose form) with the hydroxyl group at the anomeric carbon (C1) in the beta configuration (equatorial position). Galactose is the C4 epimer of glucose, meaning the configuration of the hydroxyl group at C4 is different from that of glucose. Draw the basic chair conformation of a six-membered ring: Start by sketching a cyclohexane chair structure. Label the carbon atoms from C1 to C6 in a clockwise direction, with C1 at the top right corner. Place the substituents on the ring: Add the hydroxyl groups and hydrogen atoms to each carbon based on the stereochemistry of β-D-galactopyranose. For β-D-galactopyranose: (1) At C1, place the hydroxyl group in the equatorial position and the hydrogen in the axial position. (2) At C2, place the hydroxyl group in the equatorial position. (3) At C3, place the hydroxyl group in the axial position. (4) At C4, place the hydroxyl group in the axial position (this is the key difference from glucose). (5) At C5, place the hydroxyl group in the equatorial position. (6) At C6, place the CH2OH group in the equatorial position. Verify the stereochemistry: Double-check that the substituents match the stereochemistry of β-D-galactopyranose, ensuring that the hydroxyl group at C4 is in the axial position, distinguishing it from glucose. Finalize the drawing: Clearly label the chair conformation with all substituents, ensuring the beta configuration at C1 and the correct stereochemistry at all other carbons. This will give you the chair conformation of β-D-galactopyranose.

Without referring to the chapter, draw the chair conformations of
(c) β-D-galactopyranose (the C4 epimer of glucose).

비슷한 문제에 대한 검증된 영상 답변:

주요 개념

Chair Conformation

Anomeric Carbon

Epimers