Question

When treated with base, the following compound undergoes an intramolecular aldol reaction to give a product containing a ring (yield \(78 \%\) ). CCC=CCCC(=O)CCC=O Propose a structural formula for this product.

Short answer

Answer: The structure of the aldol product formed after the intramolecular aldol reaction is CH3-C(=O)-CH2-C(-OH)-C(=O)-CH2-CH3, with a ring formed between the oxygen atom and the methyl-attached carbon.

Step-by-step solution

Identifying key functional groups

To start, we need to identify the key functional groups involved in an aldol reaction. In this case, those functional groups are an aldehyde and an enolate, which is formed from a ketone in the presence of a base. The given compound is: CCC=CCCC(=O)CCC=O We can see that there are two carbonyl groups in this molecule: a ketone (C(=O)) and an aldehyde (C=O). The enolate is formed from the ketone, and the reaction will occur between this enolate and the aldehyde group.

Forming the enolate

First, we need to form the enolate by deprotonating the α-carbon of the ketone (the carbon adjacent to the carbonyl) using a base. The α-carbon is the most acidic, as the negative charge formed after deprotonation can resonate with the carbonyl oxygen. Here's a simplified version of the deprotonation step: Ketone: CH3-C(=O)-CH2-CH2-C(=O)-CH3 Enolate: CH3-C(=O)-CH(-)-CH2-C(=O)-CH3 - + Base

Intramolecular aldol reaction

Next, the enolate will react with the aldehyde. In the intramolecular aldol reaction, the nucleophilic enolate attacks the electrophilic carbonyl carbon of the aldehyde. This forms a new carbon-carbon bond and results in the formation of a ring. The reaction can be represented as follows: Enolate: CH3-C(=O)-CH(-)-CH2-C(=O)-CH3 | + Aldehyde: C=O Ring formed

Formation of aldol product

After the new carbon-carbon bond is formed, we get the aldol product, which still contains a carbonyl group and a new hydroxyl group on the α-carbon. Finally, the ring will close to form the final product. The structure of the aldol product and the final product containing the ring can be represented as follows: Aldol product: CH3-C(=O)-CH2-CH(-OH)-C(=O)-CH2-CH3 | O-C-CH2-CH3 Final product (ring): CH3-C(=O)-CH2-C(-OH)-C(=O)-CH2-CH3 O | C-CH2-CH3 The final product is a cyclic structure containing the ring, which has been formed via an intramolecular aldol reaction.