Question

In pyrophosphoric acid, $H_4{P}_2{O}_7$, number of $\sigma -$ and $d\pi -p\pi$ bonds respectively are

• A. $8$ and $2$
• B. $6$ and $2$
• C. $12$ and zero
• D. $12$ and $2$

Answer 1

The correct option is D $12$ and $2$

$O=\stackrel{O-H}{\stackrel{|}{\underset{O-H}{\underset{|}{P}}}}-O-\stackrel{O-H}{\stackrel{|}{\underset{O-H}{\underset{|}{P}}}}=O$

The two double bonds contributes 2 $\sigma$ and 2 $d\pi -p\pi$.
There are 4 O-H groups = 4 $\sigma$ bonds
There are 6 P-O type of bonds.
Total no. of $\sigma$ bonds = 2+ 4+ 6 =12
Total no. of $d\pi -p\pi$ bonds= 2
Hence, the correct option is D.