In 1891, Emil Fischer determined the structures of glucose and the seven other d-aldohexoses using only simple chemical reactions and clever reasoning about stereochemistry andsymmetry. He received the Nobel Prize for this work in 1902. Fischer had determined thatd-glucose is an aldohexose, and he used Ruff degradations to degrade it to (+)-glyceraldehyde. Therefore, the eight d-aldohexose structures shown in Figure 23-3 are the possiblestructures for glucose.Pretend that no names are shown in Figure 23-3 except for glyceraldehyde, and usethe following results to prove which of these structures represent glucose, mannose,arabinose, and erythrose.(a) Upon Ruff degradation, glucose and mannose give the same aldopentose: arabinose.Nitric acid oxidation of arabinose gives an optically active aldaric acid. What are thetwo possible structures of arabinose?(b) Upon Ruff degradation, arabinose gives the aldotetrose erythrose. Nitric acid oxidation of erythrose gives an optically inactive aldaric acid, meso-tartaric acid. What isthe structure of erythrose?(c) Which of the two possible structures of arabinose is correct? What are the possiblestructures of glucose and mannose?(d) Fischer’s genius was needed to distinguish between glucose and mannose. Hedeveloped a series of reactions to convert the aldehyde group of an aldose to analcohol while converting the terminal alcohol to an aldehyde. In effect, he swappedthe functional groups on the ends. When he interchanged the functional groups ond-mannose, he was astonished to find that the product was still d-mannose. Showhow this information completes the proof of the mannose structure, and show how itimplies the correct glucose structure.(e) When Fischer interchanged the functional groups on d-glucose, the product was anunnatural l sugar. Show which unnatural sugar he must have formed, and show how itcompletes the proof of the glucose structure
Carbohydrates
Carbohydrates are the organic compounds that are obtained in foods and living matters in the shape of sugars, cellulose, and starch. The general formula of carbohydrates is Cn(H2O)2. The ratio of H and O present in carbohydrates is identical to water.
Starch
Starch is a polysaccharide carbohydrate that belongs to the category of polysaccharide carbohydrates.
Mutarotation
The rotation of a particular structure of the chiral compound because of the epimerization is called mutarotation. It is the repercussion of the ring chain tautomerism. In terms of glucose, this can be defined as the modification in the equilibrium of the α- and β- glucose anomers upon its dissolution in the solvent water. This process is usually seen in the chemistry of carbohydrates.
L Sugar
A chemical compound that is represented with a molecular formula C6H12O6 is called L-(-) sugar. At the carbon’s 5th position, the hydroxyl group is placed to the compound’s left and therefore the sugar is represented as L(-)-sugar. It is capable of rotating the polarized light’s plane in the direction anticlockwise. L isomers are one of the 2 isomers formed by the configurational stereochemistry of the carbohydrates.
In 1891, Emil Fischer determined the structures of glucose and the seven other d-aldohexoses using only simple
symmetry. He received the Nobel Prize for this work in 1902. Fischer had determined that
d-glucose is an aldohexose, and he used Ruff degradations to degrade it to (+)-glyceraldehyde. Therefore, the eight d-aldohexose structures shown in Figure 23-3 are the possible
structures for glucose.
Pretend that no names are shown in Figure 23-3 except for glyceraldehyde, and use
the following results to prove which of these structures represent glucose, mannose,
arabinose, and erythrose.
(a) Upon Ruff degradation, glucose and mannose give the same aldopentose: arabinose.
Nitric acid oxidation of arabinose gives an optically active aldaric acid. What are the
two possible structures of arabinose?
(b) Upon Ruff degradation, arabinose gives the aldotetrose erythrose. Nitric acid oxidation of erythrose gives an optically inactive aldaric acid, meso-tartaric acid. What is
the structure of erythrose?
(c) Which of the two possible structures of arabinose is correct? What are the possible
structures of glucose and mannose?
(d) Fischer’s genius was needed to distinguish between glucose and mannose. He
developed a series of reactions to convert the
alcohol while converting the terminal alcohol to an aldehyde. In effect, he swapped
the functional groups on the ends. When he interchanged the functional groups on
d-mannose, he was astonished to find that the product was still d-mannose. Show
how this information completes the proof of the mannose structure, and show how it
implies the correct glucose structure.
(e) When Fischer interchanged the functional groups on d-glucose, the product was an
unnatural l sugar. Show which unnatural sugar he must have formed, and show how it
completes the proof of the glucose structure
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