Concept explainers
Interpretation:
The structure of the anhydrous sugar (
Concept introduction:
舧 Chair conformations: It is the most stable conformation, which accurately shows the spatial arrangement of atoms.
舧 Equatorial bonds are parallel to the average plane of the ring, while axial bonds are perpendicular to the average plane of the ring.
舧 The conformation having bonds at the equatorial positions are more stable than those with bonds at the axial position.
舧 On flipping the cyclohexane ring, axial bonds become equatorial bonds and equatorial bonds becomes axial bond.
舧 Bulkier group acquires equatorial positions to form stable conformer due to steric factors.
舧 Sugars that have moisture content below 0.5% are said to be anhydrous sugars. They are usually high purity crystalline sugars obtained from
舧 Altrose is an aldohexose sugar with the chemical formula
舧 The most stable configuration of aldopyranoses is when the
舧 Stereochemistry: The equatorial orientation refers to the spatial arrangement of
舧 The anomeric effect is lowest for sugars with equatorial orientation, which results in lower energetic state, and consequently this type of orientation confers higher stability.
舧 The anomeric effect is highest for sugars with axial orientation, which results in higher energetic state, and consequently this type of orientation confers lower stability.
舧 The anhydrous sugar is produced when the axial
舧 Anhydrous sugar is an acetal, it is a nonreducing sugar, and therefore it is called anhydrous non-reducing sugar.
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Organic Chemistry
- All the glucose units in dextran have six-membered rings. When a sample of dextran is treated with methyl iodide and Ag2O and the product ishydrolyzed under acidic conditions, the final products are 2,3,4,6-tetra-O-methyl-d-glucose, 2,4,6-tri-O-methyl-d-glucose, 2,3,4-tri-O-methyl-d-glucose, and 2,4-di-O-methyl-d-glucose. Draw a short segment of dextran.arrow_forwardTrehalose, C12H22O11, is a nonreducing sugar that is only 45% as sweet as sugar. When hydrolyzed by aqueous acid or the enzyme maltase, it formsonly d-glucose. When it is treated with excess methyl iodide in the presence of Ag2O and then hydrolyzed with water under acidic conditions, only2,3,4,6-tetra-O-methyl-d-glucose is formed. Draw the structure of trehalose.arrow_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. 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_forward
- 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.arrow_forwardKojibiose is a reducing sugar that forms D-glucose on hydrolysis with aqueous acid. Reaction of kojibiose with iodomethane and Ag20 yields an octamethyl derivative, which can be hydrolyzed with aqueous acid to give one equivalent of 2,3,4,6-tetra-O- methyl-D-glucopyranose and one equivalent of 3,4,6-tri-O-methyl-D-glucopyranose. If kojibiose is hydrolyzed by alpha-glucosidases but not beta-glucosidases, what is its structure?arrow_forwardNonearrow_forward
- 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. When D-ribose is treated with methanol in the presence of an acid catalyst, two cyclic acetals, A and B, are formed, both with molecular formula C,H,0, These are separated, and each is treated with sodium periodate (Section 10.8C) followed by dilute aqueous acid. Both A and B yield the same three products in the same ratios. он о CHO СНО H+ CH,OH A +B ÕH 1. NalO, 2. H,0* НО CHO + CHOH + CH,OH ÕH CH,OH Isomeric cyclic acetals with molecular formula CH12O, D-Ribose (C;H1605) From this information, deduce whether the cyclic hemiacetal formed by D-ribose is four- membered, five-membered, or six-membered.arrow_forwardPropose a mechanism for this conversion and account for the fact that only the -OH on carbon 1 is transformed into an -OCH3 group.arrow_forwardWhen an optically active D-aldopentose was subjected to Kiliani-Fischer synthesis, followed by NaBH4/H2O, it produced a mixture of an optically active and an optically inactive alditol. When the same D-aldopentose was subjected to Wohl degradation followed by HNO3 it produced an optically inactive aldaric acid. Provide the structure of this D-aldopentose. Н- НО- н- H -ОН НО -H Н- -Н CH₂OH 1 A) 1 B) II C) III осн H D) IV НО осн -H Н- -OH H- H HỌ CH₂OH П -OH H -OH H Н -H CH₂OH Ш _H -OH HO -OH H- -OH H- осн -H -OH CH₂OH IV -OH CH₂OH Varrow_forward
- Myo-inositol, the most prominent naturally occurring form of inositols, is a carbocyclic polyol that plays an important role as the structural basis for a number of secondary messengers in eukaryotic cells. It is generated in vivo from the aldol cyclization of glucose-6-phosphate to myo-inositol-1-phosphatearrow_forwardMutarotation occurs when the two anomers interconvert in solution. Outline a stepwise mechanism for the acid-catalysed interconversion of glucose anomers by mutarotation. он он H,0* но OH Но Но НО ÓHarrow_forwardRibose, 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 H30*. OH Меон 1. NalO4 2. H30* A & B MEOH + products HO H. H* isomeric cyclic acetals with formula CgH1205 ÕH ÕH Ribose, C5H1005 Assuming that ribose formed a six-membered ring cyclic hemiacetal, draw the structure of compounds A and B.arrow_forward
- Organic ChemistryChemistryISBN:9781305580350Author:William H. Brown, Brent L. Iverson, Eric Anslyn, Christopher S. FootePublisher:Cengage LearningIntroduction to General, Organic and BiochemistryChemistryISBN:9781285869759Author:Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar TorresPublisher:Cengage Learning