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2. The reaction of diethyl hexanedioate (1,6-diester) gives the product ethyl 2-oxocyclopentanecarboxylate. Write reaction conditions and mechanism for the reaction. (2 mark)

User Kasmetski
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The reaction of diethyl hexanedioate (1,6-diester) to form ethyl 2-oxocyclopentanecarboxylate can be catalyzed by an acid or base.

Reaction conditions:
Catalyst: Acid or base
Temperature: Typically room temperature or slightly elevated temperature
Solvent: Organic solvent like ethanol or acetone

Mechanism:

1. Acid-catalyzed mechanism:
Step 1: Protonation of the carbonyl oxygen
The acid catalyst donates a proton to the carbonyl oxygen of diethyl hexanedioate, forming a more reactive species.

Step 2: Nucleophilic attack
An alcohol molecule, such as ethanol, acts as the nucleophile and attacks the electrophilic carbonyl carbon of the protonated diethyl hexanedioate. This leads to the formation of a tetrahedral intermediate.

Step 3: Proton transfer and elimination
In this step, a proton transfer occurs from the oxygen of the tetrahedral intermediate to the adjacent carbonyl oxygen, resulting in the loss of a water molecule. This leads to the formation of the product, ethyl 2-oxocyclopentanecarboxylate.

2. Base-catalyzed mechanism:
Step 1: Deprotonation of the diester
A base, such as sodium ethoxide (NaOEt), deprotonates one of the carbonyl oxygens of diethyl hexanedioate, resulting in the formation of an alkoxide ion.

Step 2: Nucleophilic attack
The alkoxide ion acts as the nucleophile and attacks the electrophilic carbonyl carbon of the other carbonyl group in diethyl hexanedioate. This leads to the formation of a tetrahedral intermediate.

Step 3: Proton transfer and elimination
A proton transfer occurs from the oxygen of the tetrahedral intermediate to the adjacent carbonyl oxygen, resulting in the loss of a water molecule. This leads to the formation of the product, ethyl 2-oxocyclopentanecarboxylate.

Please note that the specific reaction conditions and mechanisms might vary depending on the specific acid or base used and the reaction conditions chosen. The mechanism presented here provides a general overview of the reaction.
User Muli Yulzary
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