Question

How many banana bonds are there in diborane?

Answer 1

Hint: Diborane is the dimer of a borane molecule and has the chemical formula as ${B_2}{H_6}$ . In this compound, there are two types of bonds, one is normal covalent bond and the other one is banana bond. So, in order to know about how many banana bonds are present in diborane, we need to see its structure.

Complete answer:
Diborane is a dimer of borane molecules and it has the chemical formula as ${B_2}{H_6}$ . Diborane is an electrophile because according to octet rule, it requires fourteen electrons but it has only twelve electrons.
Now, if we look at the structure of diborane:

So, as we can see in this structure that there are four normal covalent bonds between boron and hydrogen (B-H) and the bond of B-H-B, it is the $3 - centre,2 - electron$ bond which means that there are three centres that is two borons and one hydrogen and only two electrons are present in this bond which are delocalised on these three centres.
So, we can say that the $3 - centre,2 - electron$ bond in B-H-B is known as the banana bond and there are a total two banana bonds which are present in the diborane.

Note:
As we have seen that there are two banana bonds in diborane, we know that these types of bonds are electron deficient and hence, this makes the diborane molecule electron deficient in nature. Therefore, it can be said that diborane is a strong electrophile and can accept lone pairs of electrons from a nucleophile to make covalent bonds.