24 Important Concepts 24 Important Concepts 6.wMutarotationoneamenct2.ngeshegpee Reactions of Saccharides-characteristic of onic acid Double . eductonta cetal formatior o2 24 Important Concepts 11.Dl-and Higher Sac des ynmvoheslleastoneoitneh89eBr of S Modifications-sugars can have modifie upsmay replace hydroxy group 11 11 24 Important Concepts 6. Mutarotation – attainment of equilibrium between anomers in solution; measured by changes in optical rotation 7. Reactions of Saccharides – characteristic of carbonyl, alcohol and hemiacetal groups: • Oxidation of aldehyde to an aldonic acid • Double oxidation to aldaric acids • Oxidative cleavage of vicinal diol units • Reduction to alditols • Condensations • Esterifications • Acetal formation 24 Important Concepts 8. Reducing Sugars – contain hemiacetal functions. • Reduce Tollens’s and Fehlings’s solutions • If the anomeric carbon is acetalized, the sugar becomes non-reducing. 9. Chain Lengthening – higher sugar synthesis involves chain lengthening using a cyanide ion as the source of new carbon. • Chain shortening – lower sugars are synthesized using Ruff chain shortening. 10. Fischer Proof – Utilizes chain lengthening and shortening and the symmetry properties of aldaric acids to elucidate the structures of the aldoses. 24 Important Concepts 11. Di- and Higher Saccharides – formed via ether formation between monomers. The oxygen bridge usually involves at least one of the hemiacetal hydroxyl groups. 12. Inversion of Sucrose – change in optical rotation of aqueous sucrose as equilibrium is established between its various cyclic and anomeric forms. 13. Modifications – sugars can have modified backbones. • Amino groups may replace hydroxy groups. • Other complex substituents • Missing oxygen (deoxyribose) • L enantiomers are rarely found