Benedict's reagent is a chemical that is used as a test for the presence of a free aldehyde functional group on glucose.The aldehyde is used when glucose and fructose bind together to form sucrose, and the Benedict's test is negative.Starch contains a great deal of glucose but gives a negative Benedict's test because:
A)all of the aldehyde groups on the starch are oxidized and cannot react with the Benedict's reagent.
B)glucose in starch has lost a carbon atom and cannot react with Benedict's reagent.
C)only the glucose at the end of a chain of starch will have an exposed aldehyde functional group to react with Benedict's reagent.
D)starch is not soluble in water and cannot react with Benedict's reagent.

Question

Quizplus · Accepted Answer

Starch is a polysaccharide, and only the terminal glucose units have a free aldehyde group that can react with Benedict's reagent. Most glucose units are involved in glycosidic bonds, which do not have free aldehyde groups.

Benedict's Reagent Is a Chemical That Is Used as a Test