How could the pH of the solution change reaction rate of the nucleophillic addit

Question

How could the pH of the solution change reaction rate of the nucleophillic addition of amine to a carbonyl compound?

At what pH are acetals more stable,pH>7 or pH<7, and why?

Explanation / Answer

At neutral or basic condition, that is at pH>7, carbonyl group remains unprotonated,so it is the less reactive form. At slightly acidic condition, that is at pH around 5, carbonyl oxygen get protonated and electrophilicity of carbonyl carbon increases, so reaction rate increases. At highly acidic ccondition,that is at pH lower than 3, nucleophile amine gets protonated and so it lost it's nucleophilicity,so reaction shutdown due to low concentration of free amine. Acetal has no free -OH proton which is unstable under basic condition, rather it has two -OR group(where R is - Me,-Et etc.). So it is stable under basic condition. But under acidic condition it get hydrolyzed and forms ketone, so Acetal is unstable under acidic condition. So it is more stable at pH>7.

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