Question #44977

An aldopentose $\textbf{P}$ upon oxidation with dilute $HNO_3$ yields an optically active aldaric acid. $\textbf{P}$ is subjected to Kiliani-Fischer synthesis (using $HCN$, followed by hydrolysis and reduction) to yield two aldohexoses, $\textbf{Q}$ and $\textbf{R}$. Oxidation of $\textbf{Q}$ with $HNO_3$ yields an optically inactive (meso) aldaric acid, whereas $\textbf{R}$ yields an optically active aldaric acid. $\textbf{Q}$ and $\textbf{R}$ are then individually reacted with 3 equivalents of phenylhydrazine ($\ce{PhNHNH2}$) at $100^\circ\text{C}$ to form osazones $\textbf{O}_Q$ and $\textbf{O}_R$ respectively. What is the relationship between $\textbf{O}_Q$ and $\textbf{O}_R$, and how many chiral centers are present in the osazone product?