Concept explainers
Interpretation:
The structures of D-xylose and D-lyxose are to be drawn.
Concept Introduction:
Carbohydrates are naturally occurring organic compounds. As the name implies carbohydrates are hydrates of carbon and have general formula of
Sugars are classified by the number of carbon atoms and functional group they contains. The monosaccharide glucose is called an Aldohexose as it contains six carbon atoms as well as an aldehyde functional group and fructose is known as ketohexose as it contains six carbons with a ketone functional group. Similarly, D-threose contain four carbon atom in a chain.
In Killiani-Fisher synthesis, hydrogen cyanide attacks the carbonyl group. The carbonyl carbon is converted to an asymmetric center. The
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Organic Chemistry (8th Edition)
- 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. b) Disaccharide E is a reducing sugar. It is hydrolyzed by an α-glycosidase enzyme, which means it contains an α- glycoside link. Treatment of E with Ag2O and excess Mel gives an octamethyl derivative F. Hydrolysis of F in dilute aqueous acid gives the pair of molecules shown below. Write the structures of E and F. (If the stereochemistry at a particular carbon is not determined by the above data, indicate this with a wavy line as shown below.) HO OMe OMe MeO MeO MOH OMe mOH OMe OMearrow_forwarda) 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.arrow_forwardDraw the structures (using chair conformations of pyranoses) of the following disaccharides.(a) 4-O-(a-d-glucopyranosyl)-d-galactopyranose(arrow_forward
- Which aldopentose gives the same aldaric acid as D-xylose? Which aldopentose gives the same aldaric acid as D-arabinose?arrow_forwardCompound A is a D-aldopentose that can be oxidized to an optically inactive aldaric acid B. On Kiliani-Fischer chain extension, A is converted into C and D; C can be oxidized to an optically active aldaric acid E, but D is oxidized to an optically inactive aldaric acid F. What is the structure of compound F? • Use the wedge/hash bond tools to indicate stereochemistry where it exists. You do not have to explicitly draw H atoms. If a group is achiral, do not use wedged or hashed bonds on it. • Show stereochemistry in a meso compound. • Do not include lone pairs in your answer. They will not be considered in the grading.arrow_forwardCellobiose, a disaccharide obtained by the hydrolysis of cellulose, is composed of two glucose units joined together in a 1→4-β-glycoside bond. What is the structure of cellobiose?arrow_forward
- Carbohydrates a. Compound Z is an aldopentose. If Z is oxidized with nitric acid the product is optically active. If Z undergoes one Ruff degradation and the product of that degradation is reduced to the alditol using H₂/Ni the resulting product is optically inactive. If compound Z undergoes two Ruff degradations, D-glyceraldehyde (shown below) is obtained. Draw the usual Fischer projection of Z (aldehyde at the top). (Hint: work backwards from D- glyceraldehyde.) H HIC OH CH₂OH D-Glyceraldehydearrow_forwardC. Trehalose and maltose are both dimers of glucose. However, they have considereably different reactivities. Concisely explain why these differences are observed. HO НО НО HO Но HO OH Он HO OHOH Но trehalose maltose 1. Malthose is a reducing sugar while trehalose is not. 2. Trehalose is very resistant to acid hydrolysis while maltose can be acid-hydrolyzed with ease.arrow_forwardSugar alcohols (alditols) are formed by chemically reducing aldoses or ketoses. Which one of the following sugars will give a negative Benedict's Test? aldopentoses alditols 2- Ketopentoses an aldose undergoing mutarotation in solutionarrow_forward
- A D-aldopentose A is oxidized to an optically inactive aldaric acid with HNO3. A is formed by the Kiliani–Fischer synthesis of a D-aldotetrose B, which is also oxidized to an optically inactive aldaric acid with HNO3. What are the structures of A and B?arrow_forwardPropose structural formulas for the following polysaccharides. Q.) Pectic acid is the main component of pectin, which is responsible for the formation of jellies from fruits and berries. Pectic acid is a polymer of d-galacturonic acid in the pyranose form joined by a-1,4-glycosidic bonds.arrow_forwardSuppose you have two simple sugars, D-arabinose and L-tagatose. Both sugars cyclize and form a non-reducing disaccharide with the glycosidic bond oriented in the alpha position relative to each monosaccharide's structure. Give the full biochemical name for this disaccharide.arrow_forward
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