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Multiple Choice
Which of the following is a correct Fischer projection for ?
A
A vertical line with the aldehyde group at the top, the hydroxyl groups on and on the left, and the hydroxyl group on on the right
B
A vertical line with the aldehyde group at the top, all hydroxyl groups on the left
C
A vertical line with the aldehyde group at the top, the hydroxyl groups on and on the right, and the hydroxyl group on on the left
D
A vertical line with the aldehyde group at the bottom, the hydroxyl groups on and on the right, and the hydroxyl group on on the left
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Verified step by step guidance
1
Recall that the Fischer projection of D-glucose is drawn with the aldehyde group at the top, representing the C1 carbon in the open-chain form.
Identify the stereochemistry of the hydroxyl groups on carbons 2, 3, and 4 for D-glucose: on C2, the OH is on the right; on C3, the OH is on the left; and on C4, the OH is on the right.
Understand that in a Fischer projection, horizontal lines represent bonds coming out of the plane (toward the viewer), and vertical lines represent bonds going behind the plane (away from the viewer). The positions of the OH groups on the horizontal lines determine the stereochemistry at each chiral center.
Compare each answer choice to the known stereochemistry of D-glucose: check the position of the aldehyde group (should be at the top), and verify the positions of the OH groups on C2, C3, and C4 carbons according to the pattern right-left-right.
Eliminate options that have the aldehyde group at the bottom or incorrect OH group placements, and select the Fischer projection that matches the correct stereochemical arrangement for D-glucose.