Question

Using your reaction roadmap 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 sequence of reactions needed to convert (E)-3-hexene to propyl propionate is as follows: 1. Ozonolysis: (E)-3-Hexene + O3 → 3-Hexanone + Zn, CH3COOH 2. Reduction: 3-Hexanone + NaBH4 → 3-Hexanol 3. Elimination and hydrohalogenation: 3-Hexanol + HBr → (E)-3-Hexene+ H2O → (E)-3-Hexene + 2HBr → 1,6-dibromohexane 4. Fragmentation: 1,6-dibromohexane + Zn → 1-Bromopropane 5. Nucleophilic acyl substitution: 1-BromoPropane + Propanoic acid + NaOH → Propyl Propionate + NaBr + H2O

Step-by-step solution

Convert \((E)\)-3-Hexene to 3-Hexanone

To turn the alkene into a ketone, we can use ozonolysis, which involves the use of ozone (\(O_3\)) followed by a reduction step with zinc (Zn) and acetic acid (CH3COOH). The reaction can be depicted as the following: \((E)\)-3-Hexene + \(O_3 \xrightarrow{} 3\)-Hexanone + Zn, CH3COOH

Convert 3-Hexanone to 3-Hexanol

Next, we need to reduce the ketone group to an alcohol group. It can be done using sodium borohydride (NaBH4) as the reducing agent. The reaction can be depicted as follows: 3-Hexanone + NaBH4 \(\xrightarrow{} 3\)-Hexanol

Convert 3-Hexanol to 1-Bromopropane

Now, we need to convert the 3-Hexanol into 1-Bromopropane. To do this, first, we will perform a hydrobromic acid (HBr) elimination reaction to create 3-Hexene. 3-Hexanol + HBr \(\xrightarrow{} (E)\)-3-Hexene + H2O Next, we will carry out a hydrohalogenation reaction using excess HBr to create 1,6-dibromohexane. \((E)\)-3-Hexene + 2HBr \(\xrightarrow{} 1,6\)-dibromohexane Finally, to obtain 1-Bromopropane, we can perform a zinc-mediated fragmentation reaction. 1,6-dibromohexane + Zn \(\xrightarrow{} 1\)-Bromopropane

Convert 1-Bromopropane to Propyl propionate

The last step is the conversion of 1-Bromopropane to Propyl Propionate, which involves the formation of an ester. This can be accomplished through nucleophilic acyl substitution when reacting with propanoic acid in the presence of a base, such as sodium or potassium hydroxide. 1-BromoPropane + Propanoic acid + NaOH \(\xrightarrow{}\) Propyl Propionate + NaBr + H2O In summary, the overall conversion of \((E)\)-3-hexene to propyl propionate would involve the following series of reactions: 1. Ozonolysis: \((E)\)-3-Hexene + \(O_3 \xrightarrow{} 3\)-Hexanone + Zn, CH3COOH 2. Reduction: 3-Hexanone + NaBH4 \(\xrightarrow{}\ 3\)-Hexanol 3. Elimination and hydrohalogenation: 3-Hexanol + HBr \(\xrightarrow{}\ (E)\)-3-Hexene + H2O → \((E)\)-3-Hexene + 2HBr \(\xrightarrow{} 1,6\)-dibromohexane 4. Fragmentation: 1,6-dibromohexane + Zn \(\xrightarrow{} 1\)-Bromopropane 5. Nucleophilic acyl substitution: 1-BromoPropane + Propanoic acid + NaOH \(\xrightarrow{}\) Propyl Propionate + NaBr + H2O