Which of the following is not aromatic?

Options

A.
B.
C.
D. All of these

Answer

4

Explanation

Compounds (2) and (3) are nonaromatics as they are nonplanar and have `(4n+2)pi` electrons while compound (1) is antiaromatic as it has `4n pi` electrons. In compound (2) called cycloheptatriene, one of the `C's` is `sp^(3)` hydridized, thereby preventing a completely cyclic overlapping `pi` system. In compound (3), called 3-methylenecy-clohexa-1,4-diene, the methylene C is not a part of the ring which has one `sp^(3)` hydridized C (see carbon atom numbered 6). In compound (1), called cyclobutadiene, there are only `4pi` electrons `(n=(1)/(2)`, not an integer).