Question

Which of the following statements would be INCORRECT about this compounds?

• A. All three C – N bond are of same length
• B. $C_1$ – N and $C_3$ – N bonds are of same length but shorter than $C_5$ – N bond
• C. $C_1$ – N and $C_5$ – N bonds are of different length but longer than $C_3$ – N bond
• D. $C_1$ – N and $C_5$ – N bonds are of same length but both are longer than $C_3$ – N bond.

Answer 1

Answer: (A), (B), (C)

The correct options are
A

All three C – N bond are of same length

B

$C_1$ – N and $C_3$ – N bonds are of same length but shorter than $C_5$ – N bond

C

$C_1$ – N and $C_5$ – N bonds are of different length but longer than $C_3$ – N bond

Due to steric hindrance, two of three groups – $N{O}_2$ groups i.e. at $C_1$ and $C_5$, go out of the plane with the benzene ring. So conjugation of these – $N{O}_2$ groups with benzene is slightly diminished. So the bond lengths of $C_1–N$ and $C_5–N$ are greater than the $C_3–N$.