From the cyclic structure of allose given, whether it is i) a furanose or pyranose form ii) Î±- or Î²- anomer iii) D or L sugar are to be stated. Concept introduction: The pyranose form is a cyclic hemiacetal form with a six membered ring formed by the nucleophilic addition of the â€“OH group on C 5 to the C 1 carbonyl group. The furanose form is a cyclic hemiacetal form with a five membered ring formed by the nucleophilic addition of the â€“OH group on C 5 to the C 2 carbonyl group. The orientation of â€“OH group differs in Î±- and Î²- anomers. In Î±- anomer the OH on C 1 is cis to the â€“OH at the lowest chirality center in Fischer projection, while in Î²- anomer the â€“OH on C 1 is trans to the â€“OH at the lowest chirality center in Fischer projection. D sugars have the â€“O- at C 5 on the right in the uncoiled form while L sugars have -O- at C 5 on the left. To state: From the cyclic structure of allose given, whether it is i) a furanose or pyranose form ii) Î±- or Î²- anomer iii) D or L sugar.

Question

In addition to lactose, D-galactose and D-glucose can form different heterodisaccharides. Draw the structures (Haworth projections) of the (i) a-glucose-(1→1) -a-galactose and ii) a- glucose-(1→3)-?-galactose, two examples of heterodisaccharides that can form.

Answer 1

Question

Chapter 25.SE, Problem 44AP

Interpretation Introduction

Interpretation:

From the cyclic structure of allose given, whether it is i) a furanose or pyranose form ii) Î±- or Î²- anomer iii) D or L sugar are to be stated.

Concept introduction:

The pyranose form is a cyclic hemiacetal form with a six membered ring formed by the nucleophilic addition of the â€“OH group on C₅ to the C₁ carbonyl group. The furanose form is a cyclic hemiacetal form with a five membered ring formed by the nucleophilic addition of the â€“OH group on C₅ to the C₂ carbonyl group.

The orientation of â€“OH group differs in Î±- and Î²- anomers. In Î±- anomer the OH on C₁ is cis to the â€“OH at the lowest chirality center in Fischer projection, while in Î²- anomer the â€“OH on C₁ is trans to the â€“OH at the lowest chirality center in Fischer projection.

D sugars have the â€“O- at C₅ on the right in the uncoiled form while L sugars have -O- at C₅ on the left.

To state:

From the cyclic structure of allose given, whether it is i) a furanose or pyranose form ii) Î±- or Î²- anomer iii) D or L sugar.

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