JEE Advanced 2023 Paper 2 · Q16 · Amines & Diazonium

PARAGRAPH II — A trinitro compound, 1,3,5-tris-(4-nitrophenyl)benzene, on complete reaction with an excess of Sn/HCl gives a major product, which on treatment with an excess of $NaNO_2/HCl$ at $0\,°C$ provides $P$ as the product. $P$, upon treatment with excess of $H_2O$ at room temperature, gives the product $Q$. Bromination of $Q$ in aqueous medium furnishes the product $R$. The compound $P$ upon treatment with an excess of phenol under basic conditions gives the product $S$. The molar mass difference between $Q$ and $R$ is $474$ g·mol$^{-1}$ and between $P$ and $S$ is $172.5$ g·mol$^{-1}$. The number of heteroatoms present in one molecule of $R$ is ___. [Atoms other than C and H are heteroatoms]