Problem Set 5 Key

5 points in carbohydrate chemistry mutarotation refers

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Unformatted text preview: e solution. (5 points) In carbohydrate chemistry, mutarotation refers to the occurrence of epimerization at the hemiacetal carbon atom, which is accompanied by a change in the optical rotation of the molecule. D- Glucose has two different forms, an α- and a β- anomer, which are diastereomers of each other and have their own specific rotations. Specific rotation refers to the observed angle at which plane- polarized light is rotated after being passed through a given sample. Pure α- D- Glucose will rotate plane- polarized light to a greater degree than pure β- D- Glucose. In a solution of D- Glucose, epimerization will occur and the α- and β- anomeric forms will interconvert until the glucose reaches equilibrium, which is roughly 36% α- D- Glucose and 64% β- D- Glucose. This epimerization of D- Glucose can be visualized experimentally by measuring the optical rotation of the solution as the ratio of each anomer in the solution changes. For example, if the solution started as pure α- D- Glucose, then the observed optical rotation would decrease as more β - D- Glucose forms. d. Explain how the overall architecture of carbohydrates can lead to a much larger and more diverse pool of structures when compared to that of nucleic acids or amino acids (5 points) Amino acids and nucleic acids can each only form 1 type of bond. Amino acids form peptide bonds by joining the amino- terminus and carboxyl- terminus of adjacent residues. Nucleic acids form a phosphodiester bond by joining the 2 5’- phosphate to the 3’- hydroxyl of adjacent nucleotides. Thus, there are only 2...
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This note was uploaded on 01/09/2014 for the course CH 170A taught by Professor Clemens during the Fall '13 term at Caltech.

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