JEE MainChemistryp Block Elements (Group 15, 16, 17 & 18)
Compound X, a non-planar molecule, is obtained as the hydrogen-containing product of the complete hydrolysis of peroxodisulphate. The molecular geometry of X is studied in both its gas phase and its solid phase (at 110 K ). Which of the following statements correctly describes the change in its structural parameters when X transitions from the gas phase to the solid phase?
Options
- AThe dihedral angle increases by approximately 21^ and the O-O bond length increases.
- BThe dihedral angle decreases by approximately 21^ but the O-O bond length increases.
- CThe dihedral angle decreases by approximately 21^ and the O-O bond length decreases.
- DThe molecule becomes completely planar (dihedral angle 0^ or 180^ ) in the solid phase due to lattice packing.
Correct answer
C. The dihedral angle decreases by approximately 21^ and the O-O bond length decreases.
Step-by-step solution
Compound X is hydrogen peroxide ( H ₂ O ₂ ), which is produced by the hydrolysis of peroxodisulphate. H ₂ O ₂ has a non-planar "open book" structure. Its structural parameters change depending on the phase due to intermolecular hydrogen bonding. In the gas phase, the dihedral angle is 111.5^ and the O-O bond length is 147.5 pm . In the solid phase at 110 K , the dihedral angle decreases to 90.2^ (a decrease of approximately 21^ ) and the O-O bond length decreases slightly to 145.8 pm . Thus, both the dihedral angle