Question

Using your reaction roadmap as a guide, show how to convert 1-bromopropane and carbon dioxide into 4-propyl-4-heptanol. You must use 1-bromopropane and carbon dioxide as the source of all carbon atoms in the target molecule. Show all reagents and all molecules synthesized along the way.

Short answer

Question: Describe a synthetic route to convert 1-bromopropane and carbon dioxide into 4-propyl-4-heptanol using a reaction roadmap, and identify the key functional groups and carbon frameworks involved. Answer: A synthetic route to convert 1-bromopropane and carbon dioxide into 4-propyl-4-heptanol consists of four steps: 1. Generate the Grignard reagent from 1-bromopropane by reacting it with magnesium (Mg) to form CH2CH2CH3-MgBr. 2. Extend the carbon chain by reacting the Grignard reagent (CH2CH2CH3-MgBr) with carbon dioxide (CO2), resulting in a magnesium carboxylate salt (CH2CH2CH2COOMgBr). 3. Convert the magnesium salt into the target molecule, 4-propyl-4-heptanol, by performing a Barbier reaction with another equivalent of 1-bromopropane (Br-CH2CH2CH3) in the presence of Zinc (Zn). Key functional groups involved in this synthesis include an alcohol group (-OH) and an alkyl chain (propyl group) attaching to the same carbon. The carbon frameworks involved are the Grignard reagent, magnesium carboxylate salt, and the target molecule 4-propyl-4-heptanol.

Step-by-step solution

Identify the key functional groups and carbon frameworks

In the target molecule, 4-propyl-4-heptanol, there are 2 key functional groups: an alcohol group (-OH) and an alkyl chain (propyl group) attaching to the same carbon. From the reactants given, (1-bromopropane and carbon dioxide), we can observe that we have to incorporate carbon dioxide into 1-bromopropane and convert the bromine group to an alcohol group in the final molecule.

Generating the carbon backbone

First, we need to generate the carbon backbone for 4-propyl-4-heptanol. We can do this by performing a Grignard reaction. To do this, react 1-bromopropane (Br-CH2CH2CH3) with magnesium to form the Grignard reagent (CH2CH2CH3-MgBr). 1-Bromopropane + Mg -> CH2CH2CH3-MgBr

Extending the carbon chain

Next, we need to extend the carbon chain by incorporating carbon dioxide. This can be done by reacting the Grignard reagent (CH2CH2CH3-MgBr) with carbon dioxide (CO2). The Grignard reagent will attack the electrophilic carbon center in carbon dioxide, and the magnesium will form a bond with one of the oxygen atoms, resulting in a magnesium carboxylate salt. CH2CH2CH3-MgBr + CO2 -> CH2CH2CH2COOMgBr

Convert the magnesium salt into the target molecule

Finally, we need to convert the magnesium salt into the target molecule, 4-propyl-4-heptanol, by forming the alcohol group, and adding a propyl group at the fourth carbon. To do this, perform a Barbier reaction. React the magnesium carboxylate salt (CH2CH2CH2COOMgBr) with another equivalent of 1-bromopropane (Br-CH2CH2CH3) in the presence of a more easily oxidizable metal like Zinc (Zn). CH2CH2CH2COOMgBr + Br-CH2CH2CH3 + Zn -> 4-propyl-4-heptanol Therefore, by following these four steps, we can convert 1-bromopropane and carbon dioxide into 4-propyl-4-heptanol. The overall sequence of reactions is as follows: 1) 1-Bromopropane + Mg -> CH2CH2CH3-MgBr 2) CH2CH2CH3-MgBr + CO2 -> CH2CH2CH2COOMgBr 3) CH2CH2CH2COOMgBr + Br-CH2CH2CH3 + Zn -> 4-propyl-4-heptanol