2.3 Carbohydrates

-Describe the structure of a variety of monosaccharides. -Explain how monosaccharides form to make Disaccharides.

• Simplest_ “sigle sugars” • All have 6 carbon atoms_“hexose” sugar • All are ‘Isomers’ of glucose. • Same number o C atoms as O atoms.(eg. C6H12O6) • Have a general formula and (CH2O)n • White crystalline solids • Dissolves in water to form sweet tasting solution.(Soluble)

-Monosaccharide -> polysaccharide _This done using a condensation reaction.

Study the different disaccharides kn the slide show.

Step 1: Place 2 ml of the substance in a boiling tube (substance must be in liquid form). Step 2: Add 10 drops of Benedict’s solution. Step 3: Place in a boiling water bath for 3-5 minutes.

Blue solution → no reducing sugar. Green/yellow precipitate → traces of reducing sugar. Orange/red precipitate → moderate amounts of reducing sugar. Brick red precipitate → large amount of reducing sugar.

Step 1: Boil in dilute HCl (to hydrolyse the non-reducing sugar). Step 2: Neutralise the solution by adding sodium hydrogen carbonate. Step 3: Repeat the Benedict’s test.