Question

Which of the following molecules has five σ bonds and one π bond?

(a) `"C"_2"H"_6`
(b) `"C"_2"H"_3"Cl"`
(c) `"C"_2"H"_2"Cl"`
(d) `"C"_2"H"_4`

Answer 1

The correct answer is d) `"C"_2"H"_4`.

Explanation:

a) `"C"_2"H"_6`

Ethane has six σ bonds formed by the overlap of `bb"sp"^3` and `"s"` orbitals.

b) `"C"_2"H"_3"Cl"`

This compound has only three σ bonds (the `"C-H"` bonds) formed by the overlap of `"sp"^2` and `"s"` orbitals.

c) `"C"_2"H"_2"Cl"`

This compound does not exist.

d) `"C"_2"H"_4`

Ethylene has (i) four σ bonds formed by the overlapping of `"sp"^2` and `"s"` orbitals;
(ii) one σ bond formed by overlapping of two `"sp"^2` orbital; and (iii) one π bond formed by overlap of two `"p"` orbitals.