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Ch. 23 - Carbohydrates and Nucleic Acids
Wade - Organic Chemistry 9th Edition
Wade9th EditionOrganic ChemistryISBN: 9780135213728당신이 사용하는 게 아니라요?교과서 변경
모든 교과서Wade 9th EditionCh. 23 - Carbohydrates and Nucleic Acids문제 56b
23장, 문제 56b

Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?
(b) α-D-fructofuranosyl-β-D-mannopyranoside

검증된 단계별 안내
1
Step 1: Understand the concept of reducing sugars. Reducing sugars are carbohydrates that can act as reducing agents because they have a free aldehyde group (-CHO) or a free ketone group (-C=O) in their open-chain form. These sugars can reduce mild oxidizing agents like Tollens' reagent or Benedict's solution.
Step 2: Analyze the structure of the given sugar, a-D-fructofuranosyl-b-D-mannopyranoside. This is a disaccharide composed of two monosaccharides: D-fructose (a ketose) in its furanose form and D-mannose (an aldose) in its pyranose form. The two monosaccharides are linked via a glycosidic bond.
Step 3: Determine if the glycosidic bond involves the anomeric carbons of both monosaccharides. In this case, the glycosidic bond connects the anomeric carbon of D-fructose (C2) and the anomeric carbon of D-mannose (C1). Since both anomeric carbons are involved in the bond, neither monosaccharide has a free anomeric carbon, meaning the disaccharide cannot act as a reducing sugar.
Step 4: Understand the concept of mutarotation. Mutarotation is the change in optical rotation due to the interconversion between alpha and beta anomers of a sugar in solution. For mutarotation to occur, the sugar must have a free anomeric carbon that can open to form the linear structure and then reclose to form either the alpha or beta anomer.
Step 5: Conclude whether mutarotation occurs for the given sugar. Since both anomeric carbons are involved in the glycosidic bond, the sugar cannot undergo mutarotation because neither monosaccharide can open to form the linear structure. Therefore, a-D-fructofuranosyl-b-D-mannopyranoside is neither a reducing sugar nor capable of undergoing mutarotation.

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이 영상 해법은 위 문제에 도움이 된다고 튜터들이 추천한 것입니다.
영상 길이:
11m

주요 개념

질문에 올바르게 답하기 위해 반드시 이해해야 하는 핵심 개념들은 다음과 같습니다.

Reducing Sugars

Reducing sugars are carbohydrates that can donate electrons to other molecules, typically due to the presence of a free aldehyde or ketone group. This property allows them to reduce certain chemical reagents, such as Benedict's or Fehling's solution. Common examples include glucose and fructose, which can exist in open-chain forms that contain these reactive groups.
추천 영상:
08:42
Reducing Sugars

Mutarotation

Mutarotation is the change in optical rotation that occurs when an anomeric carbon in a sugar ring opens and closes, interconverting between its alpha and beta forms. This process is significant in sugars like glucose and fructose, as it leads to a mixture of anomers in solution. The rate of mutarotation can be influenced by factors such as temperature and concentration.
추천 영상:
03:06
Mechanism

Furanose and Pyranose Forms

Furanose and pyranose refer to the cyclic forms of sugars, where furanose is a five-membered ring and pyranose is a six-membered ring. The structure of the sugar affects its reactivity and properties, including whether it can act as a reducing sugar. In the case of the sugar mentioned in the question, understanding its ring structure is crucial for determining its reducing ability and mutarotation behavior.
추천 영상:
06:23
Monosaccharides - Forming Cyclic Hemiacetals
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Which of the D-aldopentoses will give optically active aldaric acids on oxidation with HNO3?

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교과서 질문

Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?

(a) methyl β-D-glucopyranoside

(b) 2,3,4,6-tetra-O-methyl-D-mannopyranose

(c) 1,3,6-tri-O-methyl-D-fructofuranose

(d) methyl 2,3,4,6-tetra-O-methyl-β-D-galactopyranoside

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교과서 질문

Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?

(c) 6-O-(β-D-galactopyranosyl)-D-glucopyranose

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교과서 질문

Erwin Chargaff’s discovery that DNA contains equimolar amounts of guanine and cytosine and also equimolar amounts of adenine and thymine has come to be known as Chargaff’s rule:

G = C and A = T

(a) Does Chargaff’s rule imply that equal amounts of guanine and adenine are present in DNA? That is, does G = A?

(b) Does Chargaff’s rule imply that the sum of the purine residues equals the sum of the pyrimidine residues? That is, does A + G = C + T?

(c) Does Chargaff’s rule apply only to double-stranded DNA, or would it also apply to each individual strand if the double helical strand were separated into its two complementary strands?

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교과서 질문

An unknown reducing disaccharide is found to be unaffected by invertase enzymes. Treatment with an α-galactosidase cleaves the disaccharide to give one molecule of D-fructose and one molecule of D-galactose. When the disaccharide is treated with excess iodomethane and silver oxide and then hydrolyzed in dilute acid, the products are 2,3,4,6-tetra-O-methylgalactose and 1,3,4-tri-O-methylfructose. Propose a structure for this disaccharide, and give its complete systematic name.

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교과서 질문

Which of the following sugars are reducing sugars? Which ones would undergo mutarotation?

(a) 4-O-(α-D-glucopyranosyl)-D-galactopyranose

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