Question

Write chemical equations for the following reactions.
(i) Reaction of ethanolic $N{H_3}$ with ${C_2}{H_5}Cl$

Answer 1

We know that the alkyl halides are derivatives of alkanes in which hydrogen is replaced by halogens. Carbon-halogen bond is a very weak polar bond. This reaction can be done with excess of ammonia or excess of ammonia of ethyl chloride and the product formed will be different.

Complete step by step answer:
We must remember that alkyl halides are classified as primary, secondary and tertiary based on the number of carbons bonded to the carbon with the halogen atom. When ammonia is treated with ethyl chloride, it undergoes nucleophilic substitution reaction. In this reaction, ammonia acts as a nucleophile and it is a weak base and chloride will be the leaving group. Negative charge is a stronger nucleophile than an analogous neutral species $N{H_2} > N{H_3}$. Nucleophilicity increases down the periodic table.
Now we can write the chemical equation for the given reaction as,
${C_2}{H_5}Cl\xrightarrow{{N{H_3}}}{C_2}{H_5}N{H_2}\xrightarrow{{{C_2}{H_5}Cl}}{\left( {{C_2}{H_5}} \right)_2}NH\xrightarrow{{{C_2}{H_5}Cl}}{\left( {{C_2}{H_5}} \right)_2}N$
In this reaction ammonia attacks the electrophilic carbon of an alkyl halide and it removes a chloride ion and forms a new bond between carbon and nitrogen. Adding an excess amount of ethyl chloride removes the hydrogen bonded to the nitrogen atom forming secondary and tertiary amines. This mixture of products can be avoided by adding excess ammonia to the ethyl chloride.

Additional Information:
First, we see the $S{N^1}$ reaction mechanism.
The $S{N^1}$ reaction:
It is two step reactions, at first step the bond between the carbon and hydrogen breaks hydrolytically and in the second step nucleophile reacts with the carbocation formed in the first step.
The general mechanism of $S{N^1}$ reaction is,
Step 1: $R - X\xrightarrow{{Polar\,solvent}}{R^ + } + {X^ - }$
Step 2: ${R^ + } + {X^ - }\xrightarrow{{{{\left[ {OH} \right]}^ - }}}R - OH$
The $S{N^2}$ reaction:
It is a single step reaction in which the formation of carbocation and leaving of halogen take place simultaneously.
The mechanism of $S{N^2}$ reaction is,

Let us discuss the difference between $S{N^{_1}}\& S{N^{_2}}$ reactions.

$S{N^1}$ reactions	$S{N^2}$ reactions
The rate of $S{N^1}$ reaction is unimolecular.	The rate of $S{N^2}$ reaction is bimolecular.
The rate of the reaction depends on the concentration of the substance, thus it follows first order kinetics.	The rate of reaction depends on the concentration of both nucleophile and substrate. Thus, it follows second order kinetics
It is a two step process.	It is a one step process.
The intermediate formed is carbocation.	No intermediate is formed during the reaction.
No partial bond is formed	Carbon forms a partial bond with the nucleophile and the leaving group.
Optically inactive substance becomes optically active.	In $S{N^2}$ inversion of reaction takes place.

Note:
We must remember that an electron-rich species is called nucleophile; it may be anion, or compound, or atom with at least one lone pair of electrons and the opposite of nucleophile is an electrophile. Electrophile may be a positively charged species.