Question

Give reason for the following statement:

SF₆ is not easily hydrolysed though thermodynamically it should be.

Answer 1

1. SF₆ has a very stable octahedral structure with sulphur in the +6 oxidation state and fully surrounded by fluorine atoms.
2. The sulphur-fluorine bonds are very strong, and the molecule is sterically shielded, preventing water molecules from attacking sulphur.
3. The kinetic barrier is very high for the hydrolysis reaction, making it extremely slow despite being thermodynamically favourable.
4. In contrast, SF₄ is less symmetrical, and sulphur is more accessible, so it hydrolyses easily.

Thus, SF₆ is kinetically inert to hydrolysis due to strong bonds and steric hindrance.