Reaction Intermediate: Types, Carbanions & Radicals

Reaction intermediate is a short-lived species found within a multi-step reaction procedure that is produced in the previous step and later consumed in the next steps which finally produces the final reaction product. An important example of reaction intermediate is the metabolism of metabolites and nutrients. Reaction intermediate can also be explained with the help of a chemical equation.

Key Terms: Intermediate, reactive, compound, species, charge, covalent, valency, chemical reaction

What is Reaction Intermediate? 

[Click Here for Sample Questions]

During the conversion of a reactant to a product, the chemical compound formed is known as a chemical intermediate. Reactive Intermediate which is also known as chemical intermediate, is highly reactive, possesses high energy and is a temporary molecule that will change into its stable form when it is processed in a chemical reaction. In some cases, they are segregated and reserved. For example, Matrix Isolation.

In physics and chemistry, Matrix Isolation is a technique that is used for experimental purpose which includes a material that has been confined within an underactive material.

For example, consider this imaginary stepwise reaction:

A + B → C + D

The reaction includes these elementary steps:

A + B → X*

X* → C + D

The chemical species X* is an intermediate.

Types Of Reaction Intermediate

[Click Here for Sample Questions]

There are many types of reactive intermediates:

Carbanion

Carbanion is a type of reaction intermediate in organic chemistry that contains one negative charge on a carbon atom. When organic compounds are treated with a very strong base, carbanions are formed. For example, let’s consider the reaction of butane with a base. When the base removes a hydrogen atom from butane we get a carbanion as result.

Carbanion

Free Radicals

Free radicals exists in a single unpaired electron form. When a covalent bond which is made of two electrons breaks down, each of the bond's electrons is taken by every atom. For example when a carbon-hydrogen bond in methane breaks down, one of the bond's electrons goes to carbon and the other to hydrogen. 

Free Radicals

Carbocations

A chemical compound having a positive charge on carbon atoms and carrying six electrons in its valence shell are called carbocations or carbenium ions. It has a planar structure.

Carbocation

Carbenes

Carbenes are a neutral divalent carbon compound in which the carbon atoms are bonded to two other monovalent atoms or groups which also contain two non-binding electrons in it. They are highly reactive in nature and are also transient because there are only six electrons in the central carbon atom present in its valence shell and thus have a higher tendency to complete its octet form and attain stability which can only occur by gaining two more electrons.

Carbenes

Nitrenes

Nitrenes are highly reactive in nature as it is an electron-deficient species. It is a neutral monovalent nitrogen compound that has two independent pairs of electrons and is also linked to a single monovalent atom or group. They exist in both triplet and singlet states. The triplet state is comparatively more stable than the two. 

Nitrenes

Benzynes

Benzynes are another type of reactive intermediate which is aromatic in character. It is derived from benzene ring by substituting two substituents of ortho postions, one is available in the form of electrophile and the other is in the form of nucleophile, leaving behind two electrons to be disbursed between two orbital. It is neutral reactive in nature.

Features Of Reaction Intermediate

[Click Here for Sample Questions]

Chemical trapping can be used in proving its existence. The chemical trap is defined as a chemical compound that detects a molecule in some particular cases. We can understand its purpose better from the given situation below.

• When the molecules are highly reactive in nature or they cannot be regulated by any Spectroscopic means. 
• When the molecule’s concentration is below its detection limit.
• When the molecule exist within the mixture, the elements of all the component intervene with its detection.

Things to Remember

• Reactive Intermediate is a temporary molecule and highly reactive in nature, that possess high energy and will change into its stable form when it is processed in a chemical reaction. 
• Matrix Isolation is an example of a chemical intermediate. It is used for experimental purposes which includes a material that has been confined within a non-reactive material.
• There are two types of reaction intermediate i.e. carbanion and free radical.
• A carbanion is a type of reaction intermediate in organic chemistry that contains one negative charge on a carbon atom. 
• Another type of reaction intermediate is free radicals. It exists in a single unpaired electron form.

Read More: