GUJARAT SET 2022
Polyphosphonitrilic chloride, when stored in the air, makes the material brittle. This is due to the formation of:
- A. Chlorine bridges
- B. Hydrogen bridges
- C. Nitrogen bridges
- D. Oxygen bridges
Polyphosphonitrilic chloride, when stored in the air, makes the material brittle. This is due to the formation of Oxygen bridges
Explanation
Polyphosphonitrilic chloride, often referred to as "Inorganic Rubber" ([NPCl2]n), is highly sensitive to moisture in the atmosphere. The degradation process occurs in two main steps:
-
1. Hydrolysis: When exposed to air, the chlorine atoms attached to the phosphorus atoms are replaced by hydroxyl (-OH) groups from water vapor.
(NPCl2)n + 2nH2O → [NP(OH)2]n + 2nHCl
- 2. Cross-linking: These hydroxyl groups are unstable and undergo a condensation reaction with neighboring chains. This results in the formation of P—O—P linkages, also known as oxygen bridges.
Why does it become brittle?
In its pure state, the linear chains can slide past each other, giving the material its rubber-like elasticity. However, the formation of oxygen bridges creates a rigid, three-dimensional cross-linked network. This restricts chain movement, causing the material to lose its flexibility and become hard and brittle.
Note: To prevent this, these materials must be stored in vacuum-sealed containers or under inert gases like Nitrogen.