AlCl3 forms dimer in vapour phase but BCl3 does not because

Question

AlCl3 forms dimer in vapour phase but BCl3 does not because (A) In Al there are vacant p orbitals in which it accommodates lone pair from chlorine atoms (B) In B C l3 there is back bonding (C) There is hydrogen bonding in between two AlCl3 molecules in vapour phase (D) None of the above

Tardigrade Admin · Accepted Answer

The formation of stronger backbond ( 3p arrow 2p overlap in BCl3 and weaker 3p arrow 3p overlap in AlCl3 ) reduces the electron deficiency of the central atom and thus dimerisation tendency is reduced. So AlCl3 can form a dimer but BF3 and BCl3 cannot.

Q. $A lC l_{3}$ forms dimer in vapour phase but $BC l_{3}$ does not because

In $A l$ there are vacant p orbitals in which it accommodates lone pair from chlorine atoms

In $BC l_{3}$ there is back bonding

There is hydrogen bonding in between two $A lC l_{3}$ molecules in vapour phase

None of the above

The formation of stronger backbond ( $3 p \to 2 p$ overlap in $BC l_{3}$ and weaker $3 p \to 3 p$ overlap in $A lC l_{3}$ ) reduces the electron deficiency of the central atom and thus dimerisation tendency is reduced. So $A lC l_{3}$ can form a dimer but $B F_{3}$ and $BC l_{3}$ cannot.

Q. AlCl3​ forms dimer in vapour phase but BCl3​ does not because

In Al there are vacant p orbitals in which it accommodates lone pair from chlorine atoms

In BCl3​ there is back bonding

There is hydrogen bonding in between two AlCl3​ molecules in vapour phase