## Step-by-Step Solution ### 1. **Identify the Compound** The structure is **ethyl hexanoate**, an ester with the formula: ``` CH3CH2CH2CH2CH2COOCH2CH3 ``` ### 2. **Locate the Carbonyl Group** The carbonyl group (C=O) is in the ester functional group. ### 3. **McLafferty Rearrangement Overview** The McLafferty rearrangement is a mass spectrometry fragmentation process that occurs in carbonyl compounds with a γ-hydrogen (a hydrogen three carbons away from the carbonyl carbon). - **A six-membered cyclic transition state** forms, and the γ-hydrogen is transferred to the carbonyl oxygen, **cleaving the molecule**. ### 4. **Find the γ-Carbon** - **α-carbon:** Adjacent to the carbonyl (ester) carbon. - **β-carbon:** Second carbon away. - **γ-carbon:** Third carbon away. Let's number from the carbonyl carbon (in the main chain): ``` O=C-1-2-3-4-5-6 ``` γ-Hydrogen is on **carbon 3**. ### 5. **McLafferty Rearrangement Mechanism** - The γ-hydrogen is transferred to the carbonyl oxygen. - The bond between the α and β carbons breaks, resulting in: - An enol (or its tautomer) fragment **ion** - A neutral alkene fragment ### 6. **Draw the Daughter Ion** The daughter ion is the charged fragment containing the carbonyl group, now as an enol (due to the hydrogen transfer): #### **Fragment after Cleavage** - The main chain is cleaved between the α and β carbons. - The γ-hydrogen is transferred to the carbonyl oxygen. #### **Resulting Daughter Ion** For ethyl hexanoate: - The fragment containing the ester and three carbons from the main chain will remain as the ion. **Structure:** ``` [CH2=CH-COOCH2CH3]^+ ``` Or, more precisely, the enol form: ``` CH2=CH-COOCH2CH3^+ ``` Alternatively, you can show the enol tautomer as: ``` CH3-CH=COOCH2CH3^+ ``` But the important feature is the double bond between the α and β carbons. --- ## **Final Answer** ### **The daughter ion observed from McLafferty Rearrangement is:** ``` O || CH2=CH-C-OCH2CH3^+ ``` - The positive charge is typically delocalized on the oxygen. - The ion is called the **enol-ester fragment ion** (m/z = 101 for this molecule). --- ### **Summary Table** | Step | Description | |-----------------------------|---------------------------------------------| | Identify γ-carbon | 3 carbons from carbonyl | | Hydrogen transfer | γ-H to carbonyl oxygen | | Bond cleavage | Between α and β carbons | | Daughter ion | CH2=CH-COOCH2CH3^+ | --- **[Drawn structure for clarity:]** ``` H2C=CH–C(=O)–O–CH2CH3 (with a positive charge) ``` This is the daughter ion you would observe in the mass spectrum after a McLafferty rearrangement of ethyl hexanoate.