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Wednesday, July 3, 2019

Structure of phosphorous trioxide (P4O6) and phosphorous pentaoxide (P4O10) :

Phosphorous is a pentavalent element hence show +3 and +5 oxidation state (d orbital presence).it form two oxide P₂O₃ (+3) and P₂O₅ (+5). These oxide of phosphorus exist as dimer in form of P₄O₆ (+3) and P₄O₅

Comparative Study of P₄O₆ and P₄O₁₀ :

SN	Properties	P₄O₆	P₄O₁₀
1	Hybridisation (P) atom	Sp3	Sp3
2	Hybridisation (O) atom	Sp3	Sp3 /Sp2 of Vertex (O)
3	No of Bridge bond (P-O-P)	6	6
4	No of Six member ring	4	4
5	No of Total (l.p.)	16	20
6	No of Back Bond	0	4
7	No of P(pi)-P(pi) Bond	0	0
8	No of 2P(pi)-3d(pi) Bond	0	4
9	Longer (P-O) Bond	All are equal	12
10	Shorter (P-O) Bond	All are equal	4
11	Bond Length (P-O)	166 pm (Longer)	145 pm (shorter)
12	Bond Angle (O-P-O)	99.5 =100 (smaller)	102 (bigger)
13	Bond Angle (P-O-P)	127 (bigger)	123 (smaller)
14	No of Sigma Bond	12	16
15	No of (Pi) Bond	0	4
16	No of oxygen atom attached with( P)	3	4

Common feature of P₄O₆ and P₄O₁₀ :

(1) Both oxides have closed cage like structure.

(2) Both oxides contain six (P-O-P) Bond.

(3) Both oxide have 4 six member ring.

(4) Both are the anhydride of their respective acids.

(5) Both are Non planer

Explanation of Different Bond length and Bond Angle In P₄O₆and P₄O₁₀ :

(1) According to "Bent's rule" lone pair electron prefer to Stay to in those atomic hybrid orbitals have more % s-character.

(2) In case of P₄O₆ molecules, atomic hybrid orbitals containing lone pair electrons have more (s) character and less (p) character hence shorter bond length while remaining orbitals have less (S) character and more (p) character hence longer bond length (X₁) than (X₂) in P₄O_{10 .}

(3) We know that On increasing % s character in hybrid orbital, the bond length decreases while bond angle increases.

(3) In Case of P₄O₆ (O-P-O) bond angle is smaller due to higher p-character in atomic hybrid orbitals than orbital containing (O-P-O) in P₄O₁₀. (have more s-character )

For reading more Details about click on Bent Rule and Drago’s rule

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