Chapter 20: Problem 96
ln the reaction \(\mathrm{p}\) -chlorotoluene with \(\mathrm{KNH}_{2}\) in liquid \(\mathrm{NH}_{3}\) the major product is (1) 0 -toludine (2) m-toludine (3) p-toludinc (4) p-chloroanilinc
Short Answer
Expert verified
The major product is p-toluidine, which corresponds to option (3).
Step by step solution
Over 22 million students worldwide already upgrade their learning with Vaia!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Reaction Conditions
The reaction conditions for nucleophilic aromatic substitution involving p-chlorotoluene and \(\text{KNH}_2\) typically require a polar aprotic solvent. Liquid ammonia (\(\text{NH}_3\)) is an excellent choice because it can stabilize the amide ion (\(\text{NH}_2^-\)).
Liquid ammonia provides a conducive environment by solvating the nucleophile, making it more reactive. It also has a relatively low boiling point, enabling easy handling.
Employing low temperature conditions can help control the reaction rate and prevent unwanted side reactions.
Liquid ammonia provides a conducive environment by solvating the nucleophile, making it more reactive. It also has a relatively low boiling point, enabling easy handling.
Employing low temperature conditions can help control the reaction rate and prevent unwanted side reactions.
Nucleophiles
In nucleophilic aromatic substitution, the nucleophile plays a crucial role. Here, the nucleophile is the amide ion (\(\text{NH}_2^-\)).
The amide ion is highly nucleophilic due to its strong negative charge, making it effective in attacking the aromatic ring.
It preferentially substitutes the electron-withdrawing chlorine atom because chlorine creates a partial positive charge on the aromatic ring, making it more susceptible to nucleophilic attack.
The amide ion is highly nucleophilic due to its strong negative charge, making it effective in attacking the aromatic ring.
It preferentially substitutes the electron-withdrawing chlorine atom because chlorine creates a partial positive charge on the aromatic ring, making it more susceptible to nucleophilic attack.
Chemical Reagents
The primary chemical reagent in this reaction is potassium amide (\(\text{KNH}_2\)), which provides the necessary amide ion (\(\text{NH}_2^-\)).
Potassium amide is a strong base, effectively deprotonating liquid ammonia to form the essential nucleophile for the substitution.
Another reagent playing a secondary but important role is liquid \(NH_3\), which acts as the solvent. It dissolves the reactants and stabilizes the transition state, promoting the overall reaction.
Potassium amide is a strong base, effectively deprotonating liquid ammonia to form the essential nucleophile for the substitution.
Another reagent playing a secondary but important role is liquid \(NH_3\), which acts as the solvent. It dissolves the reactants and stabilizes the transition state, promoting the overall reaction.
Product Formation
Product formation in nucleophilic aromatic substitution hinges on the successful displacement of the chlorine atom by a nucleophile.
When \(\text{NH}_2^-\) substitutes for chlorine in p-chlorotoluene, the resulting major product is para-toluidine (p-toluidine).
Para-toluidine is formed because the para position (opposite to where the chlorine is attached) is more stable due to steric and electronic factors compared to ortho or meta positions. Therefore, the para-isomer is the predominant product, as observed in the problem's step-by-step solution.
When \(\text{NH}_2^-\) substitutes for chlorine in p-chlorotoluene, the resulting major product is para-toluidine (p-toluidine).
Para-toluidine is formed because the para position (opposite to where the chlorine is attached) is more stable due to steric and electronic factors compared to ortho or meta positions. Therefore, the para-isomer is the predominant product, as observed in the problem's step-by-step solution.
