p-Block Elements-I - Result Question 8
####8. $B(OH) _3+NaOH \rightleftharpoons NaBO _2+Na\left[B(OH) _4\right]+H _2 O$
How can this reaction is made to proceed in forward direction?
(2006, 3M)
(a) Addition of cis 1, 2-diol
(b) Addition of borax
(c) Addition of trans 1, 2-diol
(d) Addition of $Na _2 HPO _4$
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Answer:
Correct Answer: 8. (a)
Solution:
- Orthoboric acid is a very weak acid, direct neutralisation does not complete. However, addition of cis-diol allow the reaction to go to completion by forming a stable complex with $\left[B(OH) _4\right]^{-}$as:
$$ \underset{HO>BO \backslash OH+2 \underset{CH _2-OH}{H _{\backslash} CH _2-OH} \longrightarrow}{\underset{H _2 C-O}{H _2 C-O}>B \backslash O-CH _2+2 H _2 O} $$
