## Step-by-Step Solution ### **Step 1: Understanding the Reactants** - **Nitromethane**: CH₃NO₂ (pKₐ = 10.2) - **Sodium ethoxide**: NaOEt (a strong base) ### **Step 2: Acid-Base Properties** - **pKₐ of nitromethane (10.2)** is **much lower** than that of ethanol (conjugate acid of ethoxide, pKₐ ≈ 16). - This means nitromethane is a **stronger acid** than ethanol. - Ethoxide ion (EtO⁻) is a **strong base** and can deprotonate nitromethane. ### **Step 3: Mechanism** #### **1. Deprotonation of Nitromethane** - The ethoxide ion abstracts a proton (H⁺) from the methyl group of nitromethane. \[ \ce{CH3NO2 + EtO^- -> CH2NO2^- + EtOH} \] - **Mechanism:** 1. The lone pair on the ethoxide oxygen attacks the hydrogen on the methyl group of nitromethane. 2. The electrons from the C–H bond move onto the carbon, generating a **carbanion** (CH₂NO₂⁻). #### **2. Resonance Stabilization of the Anion** - The negative charge on the \(\ce{CH2NO2^-}\) is stabilized by resonance with the nitro group: \[ \ce{CH2NO2^- <-> ^-CH2NO2} \] - The carbanion is delocalized onto the nitro group, making the anion stable. #### **3. Salt Formation** - The resulting anion (\(\ce{CH2NO2^-}\)) associates with the sodium cation (\(\ce{Na^+}\)) from sodium ethoxide to form the salt: **sodium nitromethanide (\(\ce{Na^+ CH2NO2^-}\))**. ### **Step 4: Explanation** - **Why does a salt form?** Because nitromethane is more acidic than ethanol, ethoxide can deprotonate it. The resulting anion is resonance-stabilized, making the deprotonation favorable. The sodium cation pairs with the anion to give a salt. --- ## **Final Answer (Summary)** ### **Mechanism:** 1. **Ethoxide deprotonates nitromethane**: \[ \ce{CH3NO2 + EtO^- -> CH2NO2^- + EtOH} \] 2. **The anion is resonance stabilized** by the nitro group. 3. **Sodium cation** from sodium ethoxide associates with the anion, forming a salt (\(\ce{Na^+ CH2NO2^-}\)). **Reason:** Nitromethane's relatively low pKₐ (10.2) means it is more acidic than ethanol (pKₐ ≈ 16), so sodium ethoxide can deprotonate it, resulting in a resonance-stabilized anion that forms a salt with sodium.

# Step-by-Step Solution ## Step 1: Understanding the Reactants - **Nitromethane**: \(\ce{CH3NO2}\) (pKₐ = 10.2) - **Sodium ethoxide**: \(\ce{NaOEt}\) (a strong base) ## Step 2: Acid-Base Properties - The pKₐ of nitromethane (10.2) is significantly lower than that of ethanol (conjugate acid of ethoxide, pKₐ ≈ 16). - This indicates that nitromethane is a **stronger acid** than ethanol. - Ethoxide ion (\(\ce{EtO^-}\)) is a **strong base** capable of deprotonating nitromethane. ## Step 3: Mechanism ### 1. Deprotonation of Nitromethane - The ethoxide ion abstracts a proton (H⁺) from nitromethane: \[ \ce{CH3NO2 + EtO^- -> CH2NO2^- + EtOH} \] - **Mechanism:** 1. The lone pair on the ethoxide oxygen attacks the hydrogen on the methyl group of nitromethane. 2. The electrons from the C–H bond shift to form a **carbanion** (\(\ce{CH2NO2^-}\)). ### 2. Resonance Stabilization of the Anion - The negative charge on \(\ce{CH2NO2^-}\) is stabilized by resonance with the nitro group: \[ \ce{CH2NO2^- <-> ^-CH2NO2} \] - The carbanion is stabilized through delocalization of the negative charge onto the nitro group. ### 3. Salt Formation - The resulting anion (\(\ce{CH2NO2^-}\)) pairs with the sodium cation (\(\ce{Na^+}\)) from sodium ethoxide to form a salt: **sodium nitromethanide (\(\ce{Na^+ CH2NO2^-}\))**. ## Step 4: Explanation - **Why does a salt form?** Nitromethane's acidity allows it to be deprotonated by ethoxide. The anion formed is resonance-stabilized, making this reaction favorable. The sodium cation combines with the anion to form the salt. --- ## Final Answer (Summary) ### Mechanism: 1. **Ethoxide deprotonates nitromethane**: \[ \ce{CH3NO2 + EtO^- -> CH2NO2^- + EtOH} \] 2. **Anion Stabilization**: The anion is resonance-stabilized by the nitro group. 3. **Formation of Salt**: Sodium cation pairs with the anion to create sodium nitromethanide (\(\ce{Na^+ CH2NO2^-}\)). ### Reason: Nitromethane's relatively low pKₐ (10.2) indicates it is more acidic than ethanol (pKₐ ≈ 16), allowing sodium ethoxide to deprotonate it, producing a resonance-stabilized anion that forms a salt with sodium.