Elementary plant Biochemistry and Biotechnology (2+1)

d) Oxidation products

Oxidation products

• When aldoses are oxidized under proper conditions with different types of oxidizing agents, three types of acids are produced, namely aldonic acids, uronic acids and aldaric acids or saccharic acids

a) Aldonic acid

• Oxidation of an aldose with bromine water at neutral pH converts the aldehyde group (C1) to a carboxyl group yields Aldonic acidHydrobromous acid formed by the reaction of water with bromine acts as an oxidizing agent
• Ketoses are not readily oxidized by bromine waterAldoses are not only oxidized by bromine water but also by the alkaline iodine solution

b) Uronic acid

• When aldoses are oxidised with hydrogen peroxide (H2O2) uronic acids are formed.In this reaction only primary alcohol group(C6) is oxidized to carboxyl group, whereas the aldehyde group remains unchanged.Uronic acids are constituents of pectic polysaccharides

c) Aldaric or saccharic acid

• When aldoses are oxidised with nitric acid, saccharic acids are formedBoth aldehyde (C1)and primary alcohol groups (C6) are oxidised to carboxyl groups.Glucose on oxidation with nitric acid produces glucaric or glucosaccharic acid. the aldaric acid produced from galactose is called as mucic acid