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InterviewSolution
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Draw the structure of white phosphorus and red phosphorus. Which one of these two types of phosphorus, is more reactive and why ? Or Which allotrope of phosphorus is more reactive and why? Or Why is red phosphorus less reactive than white phosphorus. Or Draw the structural difference between white and red phosphorus. |
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Answer» Both white and red phosphorus consist of `P_(4)` tetrahedra. In white phosphorus, the various `P_(4)` molecules are held together by weak van der Waals forces of attraction. In each `P_(4)` molecule, the PPP angle is only `60^(@)` (Fig. 11.31, page 11/127) which is much smaller than the normal tetrahedral angle of `109^(@)-28`. As a result, there is considerable angle strain. Due to weaker forces of attraction and considerable angle strain, white phsphorus is very reactive. In contrast, in red phosphorus, these `P_(4)` tetrahedra are joined together throughi covalent bonds to give polymeric structure (Fig. 11.32, page 11/129). Since it is difficult to break strong covalent bond as compared to weak van der Waals forces of attraction, therefore, white phosphorus is more reactive than red phosphorus. |
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