Question

BCl₃ Does Not Exist As Dimer But BH₃ Exists As Dimer (B₂H₆). Explain Why?

Answer 1

Dimer — A dimer is a type of oligomer that is formed by chemically bonding two monomers that are simpler compounds.

Diborane$\{$ ${\mathrm{B}}_2{\mathrm{H}}_6$ $\}$ ---- It is dimer form of BH_{3 .}

It is a chemical compound consisting of boron and hydrogen.

• It is a colorless, pyrophoric gas with a repulsively sweet odor.
• it has attracted wide attention for its electronic dot structure.
• Large-sized chlorine atoms do not fit in between the small boron atoms whereas small-sized hydrogen atoms get fitted in between boron atoms.
• Hydrogen is of small size, so it easily forms a bridge without caustic steric hindrance.
• The size of chlorine is larger than boron so, it is not able to form a bridge.
• So, that BCl₃ does not exist as a dimer due to the large size of chlorine.

Thus, in this way BCl₃ does not exists as a dimer due to the large size of chlorine while BH₃ exists as a dimer B₂H₆ due to the smaller size of the H-atom.