All the boron trihalides except `Bl_3`, may be prepared by direct reaction between the elements. Boron trihalides consist of trigonal-planar `BX_3` molecules. Unlike the halides of the other elements in the group they are monomeric in the gas, liquid and solid states, `BF_3 and BCI_3` are gases, `BBr_3` is a volatile liquid and `BI_3` is a solid. Boron trihalides are Lewis acids because they form Lewis complexes with suitable bases. `BF_(3(g)) + : NH_(3(g)) to F_3B - NH_(3(g))` However, boron chlorides, bromides and iodides are susceptible (sensitive) to protolysis by mild proton sources such as water, alcohols and even amines for example `BCl_3` undergoes rapid hydrolysis. `BCl_(3(g)) + 3H_2O((l)) to3(OH)_(3(aq.)) + 3HCl_((aq.))` It is supposed that the first step in the above reaction is the formation of the complex `Cl_3B larr OH_2` which then eliminates HCl and reacts further with water. Which of the following is correct?
A
`B(OCH_3)_3` is much weaker Lewis acid than `BBr_3`
B
`B(OH)_(3(aq.))` behave as triprotic acid
C
`[H_2BO_3]_((aq.))^(-)` is a conjugate base of `H_3BO_(3(aq.))`
D
`BF_3` does not react with ethers.
Text Solution
Verified by Experts
The correct Answer is:
A
`H_3BO_3` is monobasic and `[B(OH_4)]^(-)` is conjugate base of `H_3BO_3`. Also `BF_3` (electron deficient) reacts with ether as, `R_2O + BF_3 to [R_2O to BF_3]`.
