Carbocation and Carbanion

In simpler words, carbocation and carbanion are particular types of carbon atom molecules that carry different electrical charges. Carbocation atoms are carbon plus cation, and hence, they have a positive charge. Similarly, carbanion is the combination of carbon and anion and carries negative charges. Both the molecules possess various characteristics alongside a few classifications.

Moreover, carbocation and carbanion are the foundation of chemistry. A thorough understanding of concepts is necessary to understand any chemical reactions in organic chemistry. Here we have brought a carbocation and carbanion study material curated to help you easily learn concepts.

About Carbocation and Carbanion 

The terms carbocation and carbanion are widely used in organic chemistry. Generally, these carbon atoms are reacted with various elements to obtain a reactant for other reactions, i.e., Intermediates. Carbocation and carbanions were known as carbonium ions until the 1970s. As time passed, they were classified based on their charges and the terms ‘carbocations’, and ‘carbanions’ were introduced. 

First, the idea of carbocation was given by Julius Stieglitz in 1899. However, further study & insights were provided by Wagner-Meerwein’s rearrangement study, which was proposed by German chemist Hans Meerwein in 1922. Meanwhile, the term carbanion was first coined by Everett Wallis and Frederic Adams in 1933 owing to the nature of the atom’s electric charge.

Carbocation

In brief, a carbocation is any positively charged molecule of carbon. Carbocations usually have three positive bonds and even several electrons in their atoms, and they’re in a trigonal planar shape. As carbocation bears the positive charge, they lack the electrons in their octet. As a result, they are also considered electrophiles. They usually make rapid bonds with any nucleophiles. 

The hybridisation of carbon in carbocations remains sp2. Carbocations and carbanions react with heteroatoms. Due to this, carbocations are used as intermediates for various organic reactions. Methenium (CH3+) and Ethanium (C2H7+) are the most common carbocations.

Carbanion

A carbanion can be said to be the opposite of carbocation. A carbanion is a trivalent carbon atom generally formed in the presence of base or heterolytic cleavage. Carbanions comprise an anion where carbon has overall eight valence electrons, among which it carries one unshared pair of electrons and due to which it possesses a negative charge. A carbanion is the conjugate base of a carbon acid in specific terms. However, carbanions are nucleophiles and highly reactive elements. Carbanions exist in a trigonal pyramidal arrangement. Benzylic anion (C6H5CH2-) and methide ions (CH3) are types of carbanion.

Classes of Carbocation and Carbanions

There are numerous carbocations and carbanions used for various purposes in chemistry and possess many unique characteristics. Owing to which carbocations are categorised into different groups. They are classified by the number of bonds a carbon makes with alkyl groups. 

Mainly they are distinguished on the basis of the number of bonds a carbon shares with other carbon groups. However, the carbocations and carbanions without any bonds are classified as Methyl carbocation and carbanions. Methide (CH3+) is the typical example of Methyl carbocation and Methyl carbanion. Apart from it, the carbocations are categorised into three groups; they are listed below:

1. Primary: Single bond to carbon.

2. Secondary: Two bonds to carbon. 

3. Tertiary: Three bonds to carbon. 

Stability of Carbocation and Carbanions

Carbocation and carbanions aren’t capable of further bonding. To bond with more than three carbons, it would need an extra empty p orbital, which is impossible as per the conventional octet rule. However, throughout all three classes, the stability increases as carbocations’ bonds decrease for carbanions. Hence, tertiary carbocations are the most stable carbocations, whereas primary carbanions are the most stable carbanions.

Difference between Carbocation and Carbanions

 Conclusion

As discussed above, carbocations and carbanions are the foundation of organic chemistry and are crucial elements of chemistry. From above, we learned types, uses, hybridisation, and all other necessary aspects of carbocations and carbanions. Carbocations and carbanions are mainly distinguished by the difference in their charge. Carbocations are all positive charges, and carbanions are all negative charges.