See image — GOC and Organic Chemistry Basics Chemistry Question

💡 Solution & Explanation

# Analysis of Boiling Points **Boiling point depends on intermolecular forces:** - Hydrogen bonding (strongest) → highest BP - Dipole-dipole interactions → intermediate BP - Van der Waals forces (weakest) → lowest BP **Examine each compound:** **(a) 2,4-Dinitrophenol:** Two $OH$ groups + two $NO_2$ groups - Forms extensive hydrogen bonding network - High boiling point **(b) 2,4,6-Trinitrophenol (picric acid):** Three $OH$ groups + three $NO_2$ groups - Forms very extensive hydrogen bonding - Highest boiling point among the set **(c) 2,4-Dinitrophenol isomer:** Two $OH$ groups + two $NO_2$ groups - Similar to (a), extensive hydrogen bonding - High boiling point **(d) 2,6-Dinitrophenol:** Two $OH$ groups (ortho to $NO_2$) - The ortho-positioned hydroxyl groups are **sterically hindered** by the nitro groups - **Intramolecular hydrogen bonding** (OH···O=N) occurs instead of intermolecular H-bonding - Reduced intermolecular forces between molecules - **Lowest boiling point** **Answer: (d)** has the lowest boiling point because the ortho-substitution pattern promotes intramolecular hydrogen bonding, reducing intermolecular attractive forces.