Question

Using your roadmaps as a guide, show how to convert \((E)-3\)-hexene into propyl propionate. You must use (E)-3-hexene as the source of all carbon atoms in the target molecule. Show all reagents and all molecules synthesized along the way.

Short answer

Answer: The series of reactions to convert (E)-3-hexene into propyl propionate are oxymercuration-demercuration, hydrohalogenation, formation of a Grignard reagent, reaction with carbon dioxide, and Williamson ether synthesis.

Step-by-step solution

Break the alkene double bond

To break the alkene double bond in (E)-3-hexene, we can perform an oxymercuration-demercuration reaction. This reaction adds an -OH group to one carbon of the original double bond using the reagents Hg(OAc)_2 and H_2O followed by a reduction with NaBH4. This will convert (E)-3-hexene into a 3-hexanol.

Transform 3-hexanol into 3-bromohexane

Now, we need to convert the alcohol (3-hexanol) into 3-bromohexane by using a hydrohalogenation reaction. This can be achieved by treating the alcohol with concentrated HBr (hydrobromic acid). 3-hexanol + HBr -> 3-bromohexane + H2O

Perform a Grignard reaction to obtain propylmagnesium bromide

To make the compound propyl propionate, we will need to obtain a propyl group. To achieve that, treat 1-bromopropane with magnesium metal in an ether solvent to form propylmagnesium bromide (a Grignard reagent). 1-bromopropane + Mg -> propylmagnesium bromide

React propylmagnesium bromide with carbon dioxide

To create the necessary propionate group in the target molecule, react the propylmagnesium bromide Grignard reagent formed in Step 3 with carbon dioxide (CO2). This will result in the formation of propyl propanoate. propylmagnesium bromide + CO2 -> propyl propanoate + MgBr

Convert propyl propanoate into propyl propionate

Finally, react propyl propanoate (resulting from Step 4) with 3-bromohexane (formed in Step 2) using the Williamson ether synthesis. To do this, first treat propyl propanoate with sodium hydride (NaH) to generate a nucleophilic carbanion, then add 3-bromohexane. This reaction will form the desired ester product, propyl propionate. propyl propanoate + NaH -> propyl propanoate carbanion propyl propanoate carbanion + 3-bromohexane -> propyl propionate + NaBr In summary, we have successfully converted (E)-3-hexene into propyl propionate through a series of reactions, including oxymercuration-demercuration, hydrohalogenation, a Grignard reaction, and Williamson ether synthesis.