Question

how many molecules of formic acid does d-fructose form when reacted wirh periodic acid​

Answer 1

Answer:

Yes, there are specific rules regarding the products of periodic acid cleavage of 1,2-diols (Malaprade reaction). As to the mechanism, it is illustrated here. It is similar to the mechanism for KMnO4 oxidation of 1,2-diols. The structures of the products of 1,2-cleavage of carbohydrates is a diagnostic tool used as an aid in determining their structures. The oxidative cleavage of ethylene glycol (1, Fig. 1) affords two equivalents of formaldehyde. Primary alcohols give formaldehyde. Cleavage of the first single bond in glycerol 2 necessarily affords formaldehyde and α-hydroxyacetaldehyde. Aldehydes are readily hydrated in water. As far as periodic acid is concerned, the hydrate is a 1,2-diol. Cleavage of the second C-C bond produces not only another equivalent of formaldehyde but also an equivalent of formic acid. Secondary alcohols produce formic acid via aldehydes. (continued)