Outline the mechanism for the nucleophilic substitution reaction

Question

1. Between chloroethane and excess ammonia and name the main product of the reaction

Answer 1

Hello Derick

 

Chloroethane is an alkyl halide that reacts with ammonia to form ethyl amine (an amine) as the main product.  The reaction proceeds as follows:

 

CH₃CH₂-Cl  +  NH₃  →  CH₃CH₂-NH₃⁺ Cl^-    +  NH₃    ↔  CH₃CH₂-NH₂   +  NH₄⁺ Cl^-

 

Unfortunately, I am unable to draw the mechanism with electron movements here on Wyzant since the chem drawing capability is unavailable.

 

Chloroethane is the substrate in the reaction;  ammonia is a nucleophile (an electron rich molecule).  The nitrogen atom of ammonia has a lone pair of electrons that it uses to bond to the carbon atom bonded to the Cl atom.  Chlorine is the leaving group in this reaction where it takes the electron pair from the carbon atom it is bonded to to form chloride ion (Cl^-) as a by-product.

 

Initially, the reaction between ammonia and chloroethane forms an ethyl ammonium chloride salt.  Since excess ammonia is used, a molecule of NH₃ acts as a base where the nitrogen atom uses its lone pair of electrons to remove an H⁺ (deprotonate) from the ammonium (NH₃⁺) part of the salt.  This then yields the main product, ethyl amine, and ammonium chloride as the by-product.  After deprotonation, the NH₃⁺ ion is converted to "neutral" -NH₂, which is the functional group of amines.