Question

The bonds present in borazine/borazole are:
a.) $12\sigma $,$3\pi $
b.) $9\sigma $,$6\pi $
c.) $6\sigma $,$6\pi $
d.) $9\sigma $,$9\pi $

Answer 1

Hint: Bor in borazine indicates boron and azo indicates nitrogen . As seen in structure, borazole resembles benzene in structure and benzene has 12 sigma and 3 pi bonds. structure of borazole is

Complete step by step answer:
Borazole is also known as borazine, ${{B}_{3}}{{H}_{6}}{{N}_{3}}$ is chemical formula of borazole.
In borazine, three units of BH and three units of NH are arranged alternately.
Borazole has the same number of electrons and the same structure as benzene. As it has the same number of electrons, it is isoelectronic with benzene and has same structure as benzene, so it is isostructural. So, borazine is known as inorganic benzene.
When diborane is mixed with ammonia in ratio 1:2 at 250 to 300 degree Celsius, so borazine is synthesized.
More efficient method is when lithium borohydride is treated with ammonium chloride.
Borazine follows Huckle’s rule of aromaticity and as B-N bonds have equal lengths, it may be aromatic, so as structure suggests, there are 3 pi bonds, In each pi bond , there is one single bond and double bond and there are three B-H sigma bonds, three N-H sigma bonds, six B-N sigma bonds.
The bonds present in borazine are (A) $12\sigma $, $3\pi $.

Note: Boron acts as Lewis acid as it accepts lone pair of electrons and nitrogen acts as Lewis base as it donates lone pair of electrons. Electronegativity of boron is 2.04 and nitrogen has electronegativity as 3.04, so due to electronegativity difference between boron and nitrogen , there is unequal sharing of charge.