Chemical properties of monosaccharides

Chemical properties of monosaccharides

• 1.
  Chemical Properties of Monosaccharides Sugaralcohols such as D- sorbitol, D-xylitol from D-xylose, and D-mannitol from D-mannose are used as sweeteners in many sugar-free products such as diet drinks and sugarless gum as well as products for people with diabetes. Learning Goal Identify the products of oxidation or reduction of monosaccharides; determine whether a carbohydrate is a reducing sugar.
• 2.
  Oxidation of Monosaccharides Monosaccharidesin solution • have small amounts of the open-chain form present • have an aldehyde group with an adjacent hydroxyl group that can be oxidized to carboxylic acid by an oxidizing agent such as Benedict’s
• 3.
  Oxidation of Monosaccharides Sugaracids • are produced from the oxidation of the aldehyde form as Cu2+ is reduced to Cu+ • are named by replacing the ose ending of the monosaccharide with onic acid A carbohydrate that reduces another substance (such as the open chain form of D-glucose) is called a reducing sugar.
• 4.
  Oxidation: Fructose toGlucose Fructose, a ketohexose, • contains a ketone group, which usually can’t be oxidized • can be oxidized in a basic Benedict’s solution when a rearrangement occurs between the ketone group on carbon 2 and the hydroxyl group on carbon 1 • is then converted to glucose, which produces an aldehyde group with an adjacent hydroxyl that can be oxidized
• 5.
  Oxidation: Fructose toGlucose Fructose, a ketohexose, rearranges to form glucose and is then oxidized in Benedict’s.
• 6.
  Reduction of Monosaccharides Thereduction of the carbonyl group in monosaccharides • produces sugar alcohols, which are also called alditols • converts D-glucose to the sugar alcohol D-sorbitol
• 7.
  Reducing Sugars The sugaralcohols • are named by replacing the ose ending of the monosaccharide with itol • include D-sorbitol, D-xylitol from D-xylose, and D- mannitol from D-mannose • are used as sweeteners in many sugar-free products such as diet drinks and sugarless gum
• 8.
  Study Check Write theproduct of the reduction of D-mannose. D-Mannose
• 9.
  Solution Write the productof the reduction of D-mannose. D-Mannose D-Mannitol Reduction
• 10.
  Chemistry Link toHealth: Glucose Testing • Normally, blood glucose flows through the kidneys and is reabsorbed into the bloodstream. • When the blood level exceeds about 160 mg of glucose/dL of blood, the kidneys cannot reabsorb all of the glucose, and it spills over into the urine, a condition known as glucosuria.
• 11.
  Chemistry Link toHealth: Glucose Testing • A symptom of diabetes mellitus is a high level of glucose in the urine, which can be identified using Benedict’s test.