Methyl α-D-glucopyranoside (C7H14O6) is treated with excess periodic acid, HIO4. In this reaction only cleavage of vicinal diols occurs and the ring…

In the pyranoside ring the carbon atoms $\mathrm{C2}$, $\mathrm{C3}$ and $\mathrm{C4}$ each carry a free $\mathrm{OH}$, forming two adjacent vicinal-diol cleavage sites ($\mathrm{C2{-}C3}$ and $\mathrm{C3{-}C4}$). $\mathrm{C1}$ bears the $\mathrm{OMe}$ and the ring oxygen, $\mathrm{C5}$ has the ring oxygen and $\mathrm{C6}$, and $\mathrm{C6}$ is a $\mathrm{CH_2OH}$ attached to $\mathrm{C5}$ which has no $\mathrm{OH}$, so no further diol or hydroxy-carbonyl unit is present. Two cleavages consume $2$ mol of $\mathrm{HIO_4}$ per mole of glycoside, and the middle carbon $\mathrm{C3}$ is released as formic acid. Moles of glycoside $=1.94/194=0.0100$. Moles of $\mathrm{HIO_4}=2\times0.0100=0.0200$. Mass $=0.0200\times192=3.84\ \mathrm{g}$.