Question

Which of the following compound is not aromatic?

• A. 1, 3-cyclobutene
• B. Pyridine
• C. Furan
• D. Thiophene

Answer 1

The correct option is A 1, 3-cyclobutene

(a) Number of $\pi$ electrons $=4$
$\because$ It is not equal to $4n+2$
$\therefore$ It is not an aromatic compound

(b) Number of $\pi$ electrons $=6(=4n+2)$
(Here lone pair of electrons of N does not involve in delocalisation)

(c) Number of $\pi$ electrons
$=4+2=6(=4n+2)$

(d) Number of $\pi$ electrons $=6(=4n+2)$
Thus, except $1,3-cyclobutene$, all species are aromatic in nature.

Hence option A is correct.