Which statements about Fischer projection and Haworth projection are true?

Which statements about Fischer projection and Haworth projection are true?

• A. I, III
• B. II, IV
• C. I, II, III
• D. II, III, IV

Answer: (A)

Open-chain Fischer projections and cyclic Haworth projections represent the same carbohydrate, but in different ways, so the stereochemistry you see at each chiral center is preserved even as the drawing style changes. The big idea is how substituents move when you switch from a linear form to a ring form and how the anomeric center is treated. For aldoses, when the ring closes to form a Haworth projection, the groups that are on the right side in the Fischer projection tend to point downward in the Haworth, while those on the left tend to point upward. The carbonyl carbon becomes the anomeric carbon in the ring. The OH on that anomeric carbon can be either down or up: down corresponds to the alpha form, up to the beta form (for D-sugars, the CH2OH group is usually drawn up in the Haworth, so beta places the anomeric OH on the same side as CH2OH). For ketoses, the same general idea applies, but the specific ring form and the orientation rules for substituents can differ because the ring closure involves a different carbon as the anomeric center and often yields a furanose or a pyranose form. When evaluating which statements about Fischer versus Haworth projections are true, look for ones that correctly state these conversion rules: how right- versus left-side substituents from the Fischer map to up versus down orientations in Haworth for aldoses, and how the alpha/beta designation is determined at the anomeric center in the cyclic form. If you can share the exact text of statements I–IV, I can pinpoint precisely which pair aligns with these conversion rules.

Open-chain Fischer projections and cyclic Haworth projections represent the same carbohydrate, but in different ways, so the stereochemistry you see at each chiral center is preserved even as the drawing style changes. The big idea is how substituents move when you switch from a linear form to a ring form and how the anomeric center is treated.

For aldoses, when the ring closes to form a Haworth projection, the groups that are on the right side in the Fischer projection tend to point downward in the Haworth, while those on the left tend to point upward. The carbonyl carbon becomes the anomeric carbon in the ring. The OH on that anomeric carbon can be either down or up: down corresponds to the alpha form, up to the beta form (for D-sugars, the CH2OH group is usually drawn up in the Haworth, so beta places the anomeric OH on the same side as CH2OH).

For ketoses, the same general idea applies, but the specific ring form and the orientation rules for substituents can differ because the ring closure involves a different carbon as the anomeric center and often yields a furanose or a pyranose form.

When evaluating which statements about Fischer versus Haworth projections are true, look for ones that correctly state these conversion rules: how right- versus left-side substituents from the Fischer map to up versus down orientations in Haworth for aldoses, and how the alpha/beta designation is determined at the anomeric center in the cyclic form. If you can share the exact text of statements I–IV, I can pinpoint precisely which pair aligns with these conversion rules.