once vanillin has reacted with NaOH and NaBH4, why can you only add enough HCl to...

once vanillin has reacted with NaOH and NaBH4, why can you only add enough HCl to make the pH go down to 6? what would occur mechanistically if enough HCl (too much) was added to make the pH go down to 1?

Expert Solution

Sodium borohydride or sodium hydroxide solutions are basic in nature. So for these reactions generally basic or nutral pH is recomended. But it can work upto pH=6. Because pH=6 is very mild acedic condition. This slightly acedic medium can help to controll selectivity as well as vigorisity of the reaction by reducing the reactivity of the reagents. But at pH=1, i.e., very strong acedic condition, sodium borohydride fully converted to boric acid and hydrogen and sodium hydroxide converted to sodium chloride and water. So there are no more sodium borohydride or sodium hydroxide present in the solution. So no reaction.

Hence pH > 6 is recomended for this type of reaction.

queen_honey_blossom answered 2 years ago

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