$\mathrm{B}(\mathrm{OH})_{3}+\mathrm{NaOH} \rightleftharpoons \mathrm{NaBO}_{2}+\mathrm{Na}[\mathrm{B}(\mathrm{OH})_{4}]+\mathrm{H}_{2} \mathrm{O}$ How can this reaction is made to proceed in forward direction?

(C) addition of trans 1, 2 diol

(D) addition of $\mathrm{Na}_{2} \mathrm{HPO}_{4}$

JEE Advanced · 2006 · 09 Apr 2006 · p-Block Elements

B (OH)_{3} + NaOH ⇌ NaBO_{2} + Na [B (OH)_{4}] + H_{2} O

How can this reaction is made to proceed in forward direction?

(A)addition of cis 1, 2 diol✓ Correct
(B)addition of borax
(C)addition of trans 1, 2 diol
(D)addition of $Na_{2} HPO_{4}$

Answer: (A)

Solution

The reaction proceeds in the forward direction by addition of cis-1,2-diol because it forms a chelated complex with boric acid. Chelation stabilizes the product and shifts the equilibrium forward according to Le Chatelier's principle. The cis geometry allows both hydroxyl groups to coordinate with boron simultaneously, forming a stable five- or six-membered ring.

JEE Advanced · 2006 · 09 Apr 2006 · Single correct option

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JEE Advanced · 2006 · 09 Apr 2006 · p-Block Elements

Solution

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