In which of the following carbohydrate, molecular mass increases by 84 u after complete acetylation?

Step-by-step solution

In acetylation reaction H atom of an (- OH ) group is replaced by an acetyl group (- COCH ₃ ) . This results increase in molecular mass by [(12+16+12+3 1)-1] , that as, 42 u . Increase in molecular mass =84 u Number of - OH groups = 84 u 42 u =2 The carbohydrate must be aldotriose as it contains two alcoholic groups.