Question: Why enol form of ethylacetoacetate is more stable than keto form? explain with structure.
The enol form of ethylacetoacetate is more stable than the keto form due to the presence of an intramolecular hydrogen bond.
In the keto form, the molecule exists as a carbonyl group with two adjacent carbon atoms, connected by a double bond. This double bond creates a partial positive charge on one carbon atom and a partial negative charge on the other. The adjacent carbon atom with the partial positive charge is electron deficient and can accept electrons to form a bond with a nucleophile. This makes the keto form more reactive than the enol form.
In contrast, in the enol form, the carbonyl group is converted into a hydroxyl group, which can form an intramolecular hydrogen bond with the neighboring alpha-carbon. The hydrogen bond stabilizes the molecule by providing additional electrostatic attraction between the oxygen and hydrogen atoms, resulting in a lower overall energy state.
The following diagram illustrates the difference between the two forms of ethylacetoacetate:
```
H
|
O=C--C--CH2--CH3
|| |
CH COOCH2CH3
|
OH
```
In the keto form, the carbon-carbon double bond is present between the carbonyl carbon and the alpha-carbon, while in the enol form, a hydroxyl group (-OH) is present on the alpha-carbon, and a double bond is present between the carbonyl carbon and the beta-carbon. The intramolecular hydrogen bond is formed between the hydrogen atom on the alpha-carbon and the oxygen atom on the hydroxyl group.
Overall, the presence of the intramolecular hydrogen bond in the enol form of ethylacetoacetate makes it more stable than the keto form.
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