How do you explain the formation of furanose structure for fructose while glucose forms pyranose structure with same molecular formula `C_6H_12O_6` ?

Explanation

D-glucose , an aldohexose gives the characteristics reactions of aldehydic group (e.g., with HCN tollen's reagent, fehling reagent etc.,) but penta acetate of D-glucose does not give these reactions. It means that either - CHO group is absent or it is not available for the chemical reactions in penta acetyl glucose . Infact , the aldehydic group is a part of hemiacetal structure which penta acetyl glucose has. So , it not available for reaction.