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MECHANISM OF ACID CATALYSED TAUTOMERISATION
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Step 1:
First, an acid-base reaction. The Lewis basic O atom of the carbonyl
is protonated by the acid catalyst giving an oxonium ion. |
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Step 2:
Another acid-base reaction. Removal of an a-hydrogen
by a water molecule functioning as a base allows formation of the C=C
and neutralises the positive charge on the O giving the enol and regenerates
the catalyst. |
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MECHANISM OF BASE CATALYSED TAUTOMERISATION
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Step 1:
First, an acid-base reaction. Hydroxide functions as a base and removes
the acidic a-hydrogen giving the reactive enolate. |
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Step 2:
The negative charge is resonance stabilized to the more electronegative
O
atom. |
Step 3:
An acid-base reaction. The alkoxide deprotonates a water molecule reforming
the catalyst hydroxide and the enol |
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