To draw the pyranose form of α-D-galactopyranose, β-D-galactopyranose.

Question

a) The D-aldopentose A, C5H1005, reacts with HNO3 to yield an optically active aldaric acid B. Kiliani-Fischer chain extension of A produces a pair of D-aldohexoses C and D. C is converted by HNO3 to an optically active aldaric acid, but D is converted by HNO3 to an optically inactive aldaric acid. Write acyclic Fischer projections for A, B, C, D.

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Chapter 25.SE, Problem 55AP

Interpretation Introduction

Interpretation:

To draw the pyranose form of α-D-galactopyranose, β-D-galactopyranose.

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a) The D-aldopentose A, C5H1005, reacts with HNO3 to yield an optically active aldaric acid B. Kiliani-Fischer chain extension of A produces a pair of D-aldohexoses C and D. C is converted by HNO3 to an optically active aldaric acid, but D is converted by HNO3 to an optically inactive aldaric acid. Write acyclic Fischer projections for A, B, C, D.

Ribose, a carbohydrate with the formula shown, forms a cyclic hemiacetal, which, in principle, could contain either a four-membered, five-membered, or six-membered ring. To determine which ring is formed, ribose is treated with methanol in the presence of an acid catalyst. The products are then isolated and treated with NaIO, then with H₂O*. HO OH OH OH Ribose, C5H10O5 H 9.81 ** MeOH H* A & B isomeric cyclic acetals with formula C6H12O5 Assuming that ribose formed a five-membered ring cyclic hemiacetal, draw the structure of the sodium periodate digestion products. ▼ • Use the wedge/hash bond tools to indicate stereochemistry where it exists. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner. 1. NalO4, 2. H₂O* MeOH products 4 SIF Previous Next

Ribose, a carbohydrate with the formula shown, forms a cyclic hemiacetal, which, in principle, could contain either a four- membered, five-membered, or six-membered ring. To determine which ring is formed, ribose is treated with methanol in the presence of an acid catalyst. The products are then isolated and treated with NaIO4 then with H3O+. OH HO OH OH Ribose, C5H10O5 H MeOH H* A & B isomeric cyclic acetals with formula C6H₁2O5 1. NalO4 2. H₂O* MeOH products Assuming that ribose formed a six-membered ring cyclic hemiacetal, draw the structure of the sodium periodate digestion products. • Use the wedge/hash bond tools to indicate stereochemistry where it exists. • Draw one structure per sketcher. Add additional sketchers using the drop-down menu in the bottom right corner.