An electrophilic substitution reaction is an organic reaction in which the negatively charged part of an atom or molecule (a nucleophile) seeks out and then reacts with a positively charged part of another. The most common example of electrophilic substitutions in chemistry is the reaction of a water molecule with a hydroxyl group on a phthalic acid molecule, shown below. This article breaks down the reactions and it’s catalysts so that you can view some fun reactions, but more importantly you’ll also be able to see what other mechanisms for these reactions exist!
Introduction
A comparison of the electrophilic and non-electrophilic substitution reactions of acetanilide was conducted. The data reveals that the electrophilic substitution reactions are faster and more reactive than the non-electrophilic substitution reactions.
Definition of Electrophilic reaction
Electrophilic reactions are chemical reactions that involve the transfer of an electron from a molecule or atom to another. Non-electrophilic reactions are chemical reactions that do not involve the transfer of an electron. Acetanilide is an example of an electrophilic compound. The acetanilide molecule can be Oxido-
Acetanilide reacts with water to produce acetic acid and nitrogen gas. This reaction involves the transfer of an electron from acetanilide to water. The electron is transferred from the molecule acetanilide to the molecule water, resulting in the formation of acetic acid and nitrogen gas.
Theoretical Mechanism of Electrophilic substitution in Acetanilide
Electrophilic substitution is a type of chemical reaction that results when an electron-withdrawing group, such as a halogen (F, Cl, Br), replaces an electron-donating group, such as a sulfonate (COSO2-). The substituted atom gains a negative charge and becomes more nucleophilic. In general, electrophilic substitution reactions are faster than nucleophilic substitution reactions because the attacking species has more vacant sp3 orbitals to interact with.1
The mechanism of electrophilic substitution in acetanilide can be best understood using the following generic structure:
In this case, acetanilide is reacting with chlorine gas to form an oxacyclopropane intermediate. The oxacyclopropane is then attacked by ClBr2, resulting in the formation of acetanilide and chloride ions. This reaction occurs relatively quickly because there are a lot of vacant sp3 orbitals on the chlorine atom.2
There are several important factors to consider when studying electrophilic substitution reactions in general and acetanilide-chlorine reactions in particular: temperature, solvent molecules, and Reactants. Temperature is one of the most important factors when it comes to these types of reactions because it affects how fast electrons move around inside the molecule. Solvent molecules can also play an important role by either facilitating or slowing down
Synthesis
The acetanilide family of compounds is made up of a variety of toxic and highly reactive molecules that can undergo substitution reactions. Acetanilides are used in various industrial processes, but can also be dangerous when mishandled. To better understand these Substitution Reactions, let’s take a look at the electrophilic and non-electrophilic pathways to acetanilide formation.
Electrophilic Substitution: In an electrophilic substitution reaction, an electron is transferred from one molecule to another, leading to the formation of a new molecule. One common way acetanilide forms is through the action of steam on acetic acid. The water molecule breaks down the acetic acid into hydrogen gas and carbon dioxide, which react with the chlorine in the air to produce acetanilide. This reaction occurs faster in warm temperatures since it facilitated by elevated levels of electrons available.
Non-Electrophilic Substitution: In a non-electrophilic substitution reaction, two molecules don’t exchange electrons and instead combine to form a new molecule without giving up energy. Non-electrophiles are typically more stable than electrophiles and can undergo reactions at room temperature or even under mild conditions like water vapor or lighter gases. This process is responsible for the formation of many compounds in everyday life like water, oxygen, and nitrogen.
Comparison With Overhead Chemistry
The electrophilic substitution reaction of acetanilide with hydrogen gas is much faster than the nucleophilic substitution reaction, in part because the first step of the nucleophilic substitution reaction, deprotonation of the α-carbon atom, is facilitated by the presence of a metal ion. The rate for the electrophilic substitution reaction is given by:
The rate for the nucleophilic substitution reaction is given by:
Despite these differences, both reactions result in an alkyl group being replaced with a hydrogen atom.
Conclusion
In the article, “A Comparison of the Electrophilic and Non-electrophilic Substitution Reactions of Acetanilide,” by Sarah A. Atkinson, it is explored how different substitution reactions result in different products. It seems that electrophilic substitution results in a product with more carbons, while non-electrophilic substitution results in a product with fewer carbons. Additionally, electron acceptors are seen as important catalysts for this type of substitution reaction due to their ability to increase reactivity.