NEET2013Chemistryp Block Elements (Group 13 & 14)Actual
In BF _ 3^ the B - F bond length is 1.30 Å , when BF ₃ is allowed to be treated with Me ₃ ~N , it forms an adduct, Me ₃ ~N BF _ 3^ the bond length of B - F in the adduct is
Options
- Agreater than 1.30 Å
- Bsmaller than 1.30 Å
- Cequal to 1.30 Å
- Dnone of these.
Correct answer
A. greater than 1.30 Å
Step-by-step solution
In BF ₃ , there is back bonding in between fluorine and boron due to presence of p -orbital in boron. back bonding imparts double bond characteristics. As BF ₃ forms adduct the back bonding is no longer present and thus double bond characteristic disappears. Hence, bond becomes a bit longer than earlier (1.30 Å) .