Concept explainers
Interpretation:
The Kiliani–Fischer reaction for the synthesis of epimeric aldoses is to be outlined and Fischer projection of
Concept introduction:
舧 A carbohydrate is a
舧
舧 Carbohydrates are oxidized by
舧 Aldaric acids are carbohydrates having two
舧 The molecules that are nonsuperimposable or not identical with their mirror images are known as chiral molecules.
舧 A pair of two mirror images that are nonidentical is known as enantiomers, which are optically active.
舧 The stereoisomers that are nonsuperimposable on each other and not mirror images of each other are known as diastereomers.
舧 The achiral compounds in which plane of symmetry is present internally and consists of chiral centres are known as meso compounds, but they are optically inactive.
舧 Compounds that have a plane of symmetry tend to exist in meso forms. A meso form arises when the two stereoisomers produce superimposable images, and hence, compounds having meso forms are optically inactive.
舧 The Kiliani-Fischer reaction is used for increasing the number of carbon atoms of the respective aldoses, thereby, lengthening the carbon chain of the compound. It is an effective and economic process for synthesizing monosaccharides through the hydrolysis of a cyanohydrin. Thus, it lengthens the carbon chain of the aldose by one carbon atom. It is used to produce epimers of higher aldoses from a lower aldose, that is, a single aldose produces a mixture of two diastereomeric sugars called epimers.
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Organic Chemistry
- An optically active D-aldopentose (A) produced an optically inactive alditol (B) upon treatment with H2/Pt. When the aldopentose (A) was subjected to a Ruff degradation, D-aldotetrose (C) was generated. The aldotetrose (C) gave an optically active aldaric acid (D) upon oxidation with HNO3. D-aldopentose (A) can be prepared from D-threose by a Killani Fischer synthesis. Propose structure of A through D.arrow_forwardThe following observations are obtained after a D-hexose was made to react with several reagents: (1) The reactions of a D-hexose with (a) to (d) below yields an aldaric acid (a) NH₂OH, (b) (CH3CO)₂O, NaOCOCH 3, and, (c) NaOCH3, and then, (d) HNO3, H₂O (2) HNO3 oxidation of the same D-hexose gives an aldaric acid. Predict the structures of the three (3) possible hexoses that can undergo the above reactions?arrow_forwardPredict the products formed when the following sugars react with excess acetic anhydrideand pyridine.(a) a-d-glucopyranosearrow_forward
- Given the following structure of aldose, (a) how many chiral carbons are there? (b) is it a reducing sugar? and (c) is it an L or D sugar?arrow_forwardAldohexoses A and B both undergo Ruff degradation to give aldopentose C. On treatment with warm nitric acid, aldopentose C gives an optically active aldaric acid. B alsoreacts with warm nitric acid to give an optically active aldaric acid, but A reacts to givean optically inactive aldaric acid. Aldopentose C is degraded to aldotetrose D, whichgives optically active tartaric acid when it is treated with nitric acid. Aldotetrose D isdegraded to (+)@glyceraldehyde. Deduce the structures of sugars A, B, C, and D, and useFigure 23-3 to determine the correct names of these sugars.arrow_forwardA tripeptide contains lysine (R= -(CH₂)4NH₂), phenylalanine (R= -CH₂C6H5) and glycine (R= -H). It was found that the tripeptide reacts with 2 moles of DNFB to give compound A. When compound A was treated with SOCI2, glycine was activated. When hydrolyzed, both NH₂ groups of lysine were found to be DNP-labelled. What is the structure of the tripeptide? Select one: H (CH₂)2NH2 CH NH CH H₂N O O H₂N H₂N H₂N C (CH2)4NH2 CH 010 (CH2)4NH2 CH C=O CH,Ph CH NH NH NH CH CH,Ph CH H 010 CH CH,Ph CH (CH2)4NH2 ΝΗ NH NH NH CH,Ph CH H CH COOH H CH COOH COOH COOHarrow_forward
- Give the products of periodic acid oxidation of each of the following. How many moles of reagent will be consumed per mole of substrate in each case? (a) d-Arabinose (b) d-Ribose (c) Methyl β-d-glucopyranosidearrow_forwardThere are three (3) vials labeled A, B, and C known to contain the following monosaccharides. All three samples reduce Tollens and Fehling. By oxidation with dilute HNO3 an optically active aldaric acid is obtained for sample A and the remaining two give products without optical activity. When the three samples were subjected to an alkaline medium, it was observed that, after a certain time, samples A and C reached the same value of the specific rotation [α]. Select the RIGHT alternative: (a) Sample A is Galactose. (b) Sample B is Alosa. (c) Samples A and C are not related to each other by an epimerization process. (d) Sample C is Talose. (e) Samples B and C are epimers.arrow_forwardWhat is the product of the starting material D-glyceraldehyde which will (1) produce aldaric acid upon reacting with HNO3 + H2O, NaOCH2, NH2OH, and (CH3CO)2O + NaOCOCH3 (2) produce tartaric acid upon reacting with HNO3 + H2O, NaOCH3, NH2OH, and (CH3CO)2O + NaOCOCH3arrow_forward
- What is the product (from the image below) of the starting material D-glyceraldehyde which will (1) produce aldaric acid upon reacting with HNO3 + H2O, NaOCH2, NH2OH, and (CH3CO)2O + NaOCOCH3 (2) produce tartaric acid upon reacting with HNO3 + H2O, NaOCH3, NH2OH, and (CH3CO)2O + NaOCOCH3arrow_forwardEmil Fischer synthesized l-gulose, an unusual aldohexose that reduces to give d-glucitol.Suggest a structure for this l sugar, and show how l-gulose gives the same alditol asd-glucose. (Hint: d-Glucitol has ¬CH2OH groups at both ends. Either of these primaryalcohol groups might have come from reduction of an aldehyde.)arrow_forward3a. 3b. 3c 3d. 3e. CO₂ clavulanic acid CH₂-OH H Answer the following questions about clavulanic acid. Does clavulanic acid inhibit D-alanyl-D-alanine transpeptidase? Does clavulanic acid contain a ß-lactam? Does clavulanic acid contain a thiazolium ring? What is the result of the treatment of penicillinase with clavulanic acid? Does clavulanic acid form a covalent acyl-enzyme intermediate with penicillinase?arrow_forward