Question

Show how to prepare each alcohol by treating an ester with a Grignard reagent. (a) OC(C1CCCC1)C1CCCC1 (b) C=CCC(O)(CC=C)c1ccccc1

Short answer

Question: Show how to prepare each alcohol by treating an ester with a Grignard reagent for the following molecules: (a) OC(C1CCCC1)C1CCCC1 and (b) C=CCC(O)(CC=C)c1ccccc1. Answer: (a) Prepare the alcohol OC(C1CCCC1)C1CCCC1 by treating the ester C(=O)OC1CCCC1 with the Grignard reagent [Mg+][Br-]CCCCC1CCCC1. (b) Prepare the alcohol C=CCC(O)(CC=C)c1ccccc1 by treating the ester c1ccccc1C(=O)O with the Grignard reagent [Mg+][Br-]C=CCC(O)CC=C.

Step-by-step solution

Identify the ester to be used in the Grignard reaction

To identify the ester, we must first identify the main alcohol group present in the target molecule. In this case, it is the alcohol group connected to the cyclopentyl group. We will break the alcohol molecule down just before the oxygen, forming two parts, R1 and R2. The ester will be R1-C(=O)OR3, where R1 is derived from the target alcohol molecule and R3 is the alkyl part from the Grignard reagent. For the molecule (a), R1 is C1CCCC1, making the ester structure: C(=O)OC1CCCC1 Step 2

Identify the Grignard reagent to be used in the Grignard reaction

Now that we have the ester, we need to find the Grignard reagent that will provide the remaining R2 group (C1CCCC1) of the target alcohol molecule. The Grignard reagent has the general structure RMgX, where R is the desired alkyl group and X is a halogen atom (such as Cl, Br, or I). In this case, we are looking for a Grignard reagent with R = C1CCCC1, producing the structure: [Mg+][Br-]CCCCC1CCCC1 Step 3

Show the reaction between the ester and the Grignard reagent

Now we can write down the reaction between the ester and the Grignard reagent using the identified structures: C(=O)OC1CCCC1 + [Mg+][Br-]CCCCC1CCCC1 -> OC(C1CCCC1)C1CCCC1 + [Mg+][Br-] We have now shown how to prepare the alcohol (a) by treating an ester with a Grignard reagent. Case (b): C=CCC(O)(CC=C)c1ccccc1 Step 1

Identify the ester to be used in the Grignard reaction

The main alcohol group in the target molecule is the one attached to the ring and adjacent to the CC=C and C=CC group. We break the alcohol structure down just before the oxygen atom, and for molecule (b), R1 is cc1ccccc1. This gives us the ester structure: c1ccccc1C(=O)O Step 2

Identify the Grignard reagent to be used in the Grignard reaction

The Grignard reagent should provide the R2 group (C=CCC(O)CC=C). We are looking for a Grignard reagent with R = C=CCC(O)CC=C, producing the structure: [Mg+][Br-]C=CCC(O)CC=C Step 3

Show the reaction between the ester and the Grignard reagent

Now we can write down the reaction between the ester and the Grignard reagent using the identified structures: c1ccccc1C(=O)O + [Mg+][Br-]C=CCC(O)CC=C -> C=CCC(O)(CC=C)c1ccccc1 + [Mg+][Br-] We have now shown how to prepare the alcohol (b) by treating an ester with a Grignard reagent.