cyclic structure of glucose

CYCLIC STRUCTURE OF GLUCOSE : 

CYCLIC STRUCTURE OF GLUCOSE How we come to know of its cyclic nature?? Poonam Panchal

REACTIONS THAT CAN NOT BE EXPLAINED BY OPEN CHAIN STRUCTURE : 

REACTIONS THAT CAN NOT BE EXPLAINED BY OPEN CHAIN STRUCTURE 2,4- DNP TEST (FOR ALDEHYDE GROUP)– NEGATIVE SCHIFF’S TEST(FOR ALDEHYDE GROUP)– NEGATIVE REACTION WITH HYDROXYLAMINE (NH2OH)— CONFIRMS PRESENCE OF CARBONYL GROUP FURTHER REACTION OF PENTAACETATE OF GLUCOSE WITH HYDROXYLAMINE– NEGATIVE INDICATING ABSENCE OF FREE –CHO GROUP

REACTIONS THAT CAN NOT BE EXPLAINED BY OPEN CHAIN STRUCTURE : 

REACTIONS THAT CAN NOT BE EXPLAINED BY OPEN CHAIN STRUCTURE -Form of glucose-------crystallization from conc. Solution of glucose at 303K ß-form of glucose--------crystallization from hot and saturated aqueous solution at 371K.

Problem solved : 

Problem solved BY CYCLIC HEMIACETAL STRUCTURE

Compare Alpha and Beta Glucose : 

Compare Alpha and Beta Glucose The position of the -OH group on the anomeric carbon (#1) is an important distinction for carbohydrate chemistry. The Beta position is defined as the -OH being on the same side of the ring as the C # 6. In the chair structure this results in a horizontal projection. The Alpha position is defined as the -OH being on the opposite side of the ring as the C # 6. In the chair structure this results in a downward projection. The alpha and beta label is not applied to any other carbon - only the anomeric carbon, in this case # 1.

fructose : 

fructose Structure

Open chain structure of fructose : 

Open chain structure of fructose

Ring structure of fructose : 

Ring structure of fructose

Furan and pyran rings : 

Furan and pyran rings FURAN PYRAN

CLASSIFICATION OF CARBOHYDRATES : 

CLASSIFICATION OF CARBOHYDRATES

ON THE BASIS OF HYDROLYSIS : 

ON THE BASIS OF HYDROLYSIS MONOSACCHARIDES Can not be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone e.g. glucose,fructose,ribose OLIGOSACCHARIDES Yield 2 to 10 monosaccharide units, on hydrolysis. Disaccharides, trisaccharides, tetrasaccharides POLYSACCHARIES Called Non-Sugars Yield a large number of monosaccharide units e.g. Starch, cellulose,glycogen

On the basis of reactions : 

On the basis of reactions REDUCING SUGARS All those carbohydrates which reduce Fehling’s solution and Tollen’s reagent are referred to as reducing sugars. e.g. all monosaccharides NONREDUCING SUGARS Do not have free carboxyl group. e.g. sucrose