Question

Double bond equivalent of cubane is:

A.$4$
B. $5$
C. $6$
D. $7$

Answer 1

Hint:
Double bond equivalent is used to calculate the number of unsaturation present in an organic molecule. The term unsaturated means a double bond or a ring in a molecule structure. It is the total number of pi bonds present in the structure.
Formula used:
$DBE=C+1-\dfrac{H}{2}+\dfrac{N}{2}$
where, $DBE$ is the double bond equivalent, $C$ is the number of carbon atoms, $H$ is the number of hydrogen atoms, $N$ is the number of nitrogen atoms in the molecule.

Complete step by step answer:
An unsaturated molecule is a molecule that contains double bond and triple bond and can undergo additional reactions. For example, alkenes contain one double bond and have a general formula ${{C}_{n}}{{H}_{2n}}$. Double bond equivalent is used to calculate the level of unsaturation in a molecule. The formula used for double bond equivalent is:
 $DBE=C+1-\dfrac{H}{2}+\dfrac{N}{2}$
where, $DBE$ is the double bond equivalent, $C$ is the number of carbon atoms, $H$ is the number of hydrogen atoms, $N$ is the number of nitrogen atoms in the molecule.
The molecular formula of cubane is ${{C}_{8}}{{H}_{8}}$. Here, the number of carbon atoms is $8$, the number of hydrogen atoms is $8$ and the number of nitrogen atoms is $0$.
On substituting the values in the above formula, we get,
 $DBE=8+1-\dfrac{8}{2}+\dfrac{0}{2}$
 $\Rightarrow DBE=5$
Therefore, the double bond equivalent of cubane is $5$.

Hence, the correct option is (B).

Additional information:
Cubane is a solid crystalline substance that has a molecular formula ${{C}_{8}}{{H}_{8}}$ and consists of eight carbon atoms that are arranged at the corners of a cube and one hydrogen atom is attached to each carbon atom. It is a synthetic hydrocarbon molecule.

Note: The structure of cubane contains six rings that correspond to the six faces of a cube.
-The molecular formula of cubane is ${{C}_{8}}{{H}_{8}}$.It is a solid crystalline substance and a member of prismanes.
-Double bond equivalent is used to determine the degree of unsaturation in a molecule.