Sodium methoxide is a strong base and nucleophile. What would be the product of an S2 reaction of sodium methoxide and ethyl iodide? Write a chemical reaction with organic structures.
The Correct Answer and Explanation is :
The reaction between sodium methoxide (NaOCH₃) and ethyl iodide (C₂H₅I) undergoes an S₂ (bimolecular nucleophilic substitution) mechanism. Here’s the chemical reaction and a detailed explanation of the process:
Chemical Reaction:
CH₃O⁻ + C₂H₅I → CH₃CH₂O⁻ + I⁻
This reaction can be described step by step:
- Nucleophilic Attack: Sodium methoxide (CH₃O⁻) is a strong nucleophile, meaning it has a high affinity for electrophilic carbon atoms. In this reaction, CH₃O⁻ attacks the carbon of ethyl iodide (C₂H₅I) from the opposite side of the leaving group, which is iodine (I⁻). This attack happens in a single, concerted step without the formation of intermediates. The transition state involves the partial bond formation between CH₃O⁻ and the carbon of ethyl iodide while the C-I bond starts to break.
- Backside Attack: Since this is an S₂ mechanism (bimolecular), the nucleophile must approach the electrophilic carbon from the opposite side of the leaving group (iodine). This leads to an inversion of configuration at the carbon center, meaning the orientation of the substituents around the carbon changes from one side to the other.
- Leaving Group Departure: As the nucleophile attacks the carbon, the iodine atom (I⁻) leaves, taking its electrons with it and forming the iodide ion (I⁻).
- Product Formation: The resulting product is ethyl methoxide (CH₃CH₂O⁻), a strong base and nucleophile, and the iodide ion (I⁻).
Explanation:
The S₂ reaction is characterized by a one-step process in which the nucleophile and the leaving group interact simultaneously. The strong nucleophile (CH₃O⁻) and the good leaving group (I⁻) make this reaction proceed efficiently. The rate of the reaction depends on both the concentration of the nucleophile (sodium methoxide) and the ethyl iodide substrate, following the second-order kinetics typical of an S₂ mechanism. This is in contrast to the S₁ mechanism, which involves the formation of a carbocation intermediate.
Sodium methoxide’s role as a strong nucleophile and its basicity ensures that it will effectively displace the iodide ion, leading to the formation of ethyl methoxide.