Organic Chemistry Carbohydrates
1. What experimental results do you expect to see from Bial's Test with the following types of sugars. Answer with a specific qualitative observation or "N/A, not applicable". 1 point each
a. Pentoses
b. Hexoses
c. Disaccharides & polysaccharides
2. Name the chemical that pentoses produce when they dehydrate under acidic conditions. This chemical then reacts with the orcinol and ferric chloride in Bial's reagent to produce a colored condensation product, which is the positive test result.
3. What experimental results do you expect to see from Benedict's Test with the following types of sugars? Answer with a specific qualitative observation or "N/A, not applicable".
a. Monosaccharides
b. Polysaccharides
4. What is the structural difference that determines whether or not a disaccharide will give a positive test result with Benedict's reagent?
5. Write a chemical equation for the formation of the red precipitate in the Benedict's test. Must the sugar be in the open-form or cyclic form to reduce the Benedict's reagent?
6. Why does starch produce a blue/black colored solution with iodine? Why does the blue/black color disappear when sodium thiosulfate is added?
7. What is the procedure added as a modification to Part E, Hydrolysis of Sucrose, meant to demonstrate?
8. Write the structures of the products for the acid hydrolysis of sucrose. What is the purpose of testing the resulting hydrolysis solution with Benedict's reagent?