Question

Using your roadmaps as a guide, show how to convert 1-bromopropane and carbon dioxide into 4 -heptanone. 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: Convert 1-bromopropane and carbon dioxide into 4-heptanone using a step-by-step procedure. Answer: To convert 1-bromopropane and carbon dioxide into 4-heptanone, follow the steps below: 1. Convert 1-bromopropane into Grignard reagent (propyl magnesium bromide) by reacting with magnesium metal in diethyl ether solvent. 2. React the Grignard reagent with carbon dioxide, forming a magnesium carboxylate salt via carboxylation. 3. Hydrolyze the magnesium carboxylate salt with dilute hydrochloric acid, forming a carboxylic acid. 4. Convert the carboxylic acid into an acid chloride (e.g., butanoyl chloride) using thionyl chloride. 5. React the acid chloride with the Grignard reagent formed in step 1, followed by hydrolysis to form 4-heptanone.

Step-by-step solution

Formation of Grignard reagent from 1-Bromopropane

Start by converting 1-bromopropane into a Grignard reagent. React 1-bromopropane with magnesium metal in diethyl ether solvent. The resulting Grignard reagent is propyl magnesium bromide. This step is essential for allowing the carbon in 1-bromopropane to form new carbon-carbon bonds in later steps. \[ C_3H_7Br + Mg \xrightarrow{Et_2O} C_3H_7MgBr \]

Carboxylation of Grignard Reagent with Carbon Dioxide

Next, react the Grignard reagent (propyl magnesium bromide) with carbon dioxide. This reaction, called carboxylation, forms a new carbon-carbon bond and results in a magnesium carboxylate salt. \[ C_3H_7MgBr + CO_2 \rightarrow C_3H_7COOMgBr \]

Hydrolysis of Magnesium Carboxylate Salt

Now, hydrolyze the magnesium carboxylate salt with dilute hydrochloric acid to form the corresponding carboxylic acid. This step is necessary for creating a stable product that can be reacted further in later steps. \[ C_3H_7COOMgBr + HCl \rightarrow C_3H_7COOH + MgBrCl \]

Formation of Acid Chloride from Carboxylic Acid

Turn the carboxylic acid (butanoic acid) from the previous step into an acid chloride by reacting it with thionyl chloride. This forms butanoyl chloride. \[ C_3H_7COOH + SOCl_2 \rightarrow C_3H_7COCl + SO_2 + HCl \]

Reacting Acid Chloride with Grignard Reagent

Finally, react the acid chloride (butanoyl chloride) with the Grignard reagent formed in step 1 (propylmagnesium bromide) followed by hydrolysis to form 4-heptanone. This step results in the formation of the target molecule. \[ C_3H_7COCl + C_3H_7MgBr \rightarrow C_6H_{13}C(=O)MgBr + HCl \] \[ C_6H_{13}C(=O)MgBr + H_2O \rightarrow C_6H_{13}C(=O)H + MgBrOH \] The final product, 4-heptanone, is obtained through this multistep process with the starting materials of 1-bromopropane and carbon dioxide, as required.