Chemistry

Difference Between Carbocation and Carbanion

Main difference

The main difference between carbocation and carbanion is that carbocation comprises a carbon atom that has a positive charge while carbanion comprises a carbon atom that has a negative charge…

Carbocation versus carbanion

A carbocation is an ion that has a carbon atom that is positively charged, while a carbanion is an ion that has a carbon atom that is negatively charged. The carbon atom of the carbocation that has a positive charge is sp 2 hybridized, while the carbon atom of the carbanion that has a negative charge is sp 3hybridized The geometry of the carbon atom in the carbocation is trigonal planar; on the other hand, the geometry of the carbon atom in the carbanion is pyramidal. The magnetic properties of the carbocation are paramagnetic; on the contrary, the magnetic properties of the carbanion are diamagnetic. In various chemical reactions, the carbocation acts as an electrophile; conversely, in many chemical reactions, the carbanion acts as a nucleophile. A carbocation is more stabilized than the carbanion due to the presence of three donor methyl groups that donate electrons and thus greatly stabilize the positive charge. A carbocation is an electron deficient species; on the other hand, carbanion is an electron-rich species. The central carbon atom of the carbocation has 6 electrons in the outermost shell,

Comparison chart
Carbocation Carbanion
A carbocation is an ion that has a positively charged central carbon atom. A carbanion is an ion that has a negatively charged central carbon atom.
Hybridization
The carbon atom is sp2 hybridized. The carbon atom is sp 3 hybridized.
Geometry
flat trigon Pyramidal
magnetic properties
Paramagnetic diamagnetic
reactions
acts as an electrophile acts as a nucleophile
Stabilization
More stabilized due to the presence of three donor methyl groups that donate electrons and thus greatly stabilize the positive charge. less stabilized
number of electrons
An electron deficient species An electron-rich species
Electrons in the outermost shell
6 electrons in the outermost shell 8 electrons in the outermost shell
accept/donate an electron pair
Largely accepts an electron pair from a nucleophile to produce a covalent bond Normally a pair of electrons is donated to an electrophile to produce a covalent bond.

What is carbocation?

The term carbocation is generally defined as an ion whose central carbon atom is positively charged. Carbocation generally refers to the entire molecule, it does not just represent the positively charged carbon atom and can have one or more positive charges on its central atom. A carbocation is normally unstable because due to loss of electrons, the p orbitals of the central carbon atom are free. That is why the carbocation is very rarely or frequently reactive with other ions, but this favors the reaction between the carbocation and a nucleophile to occur because in various chemical reactions the carbocation acts as an electrophile. But the carbocation is more stabilized than the carbanion due to the presence of three donor methyl groups that donate electrons and thus greatly stabilize the positive charge. The magnetic properties of the carbocation are paramagnetic due to incomplete pairing of electrons. Characteristically, the carbon atom of the carbocation that has a positive charge is sp2 hybridized because a carbon atom can have only three bonds around its structure. The geometry of the carbon atom in the carbocation is trigonal planar. The central carbon atom of the carbocation has 6 electrons in the outermost shell. A carbocation is divided into four categories consistent with the number of carbon atoms from which the positively charged carbon atoms bond.

types of carbonation
  • methyl carbocation
  • primary carbonation
  • secondary carbonation
  • Tertiary carbonation

What is Carbanion?

The term carbanion is generally defined as an ion whose central carbon atom is negatively charged. The central carbon atom that has a negative charge is sp 3hybridized The geometry of the carbon atom in the carbanion is pyramidal only except for the benzylcarbanion. The outermost shell of the carbanion has 8 electrons, which means it obeys the octet rule. This octet rule is formed by removing positively charged atoms or groups from a neutral molecule. In many chemical reactions, the carbanion almost always acts as a nucleophile and readily reacts with an electrophile to form a covalent bond. The magnetic properties of the carbanion are diamagnetic because the combination of electrons is complete. The smallest carbanion considered is the “meturo ion”, which is formed from methane from the loss of a proton. Four main types of carbanion are discussed below.

Types of carbanion

  • methyl carbanion
  • primary carbanion
  • Secondary carbanion
  • tertiary carbanion

Key differences

  1. Carbocation having a central carbon atom that is positively charged while carbanion has a carbon atom that is negatively charged.
  2. The carbon atom of the carbocation is sp 2 hybridized , while the negatively charged carbon atom of the carbanion is sp 3
  3. The structure of the carbon atom in a carbocation is planar trigonal; on the other hand, the geometry or structure of the carbon atom in the carbanion is pyramidal.
  4. The attractive properties of the carbocation are paramagnetic; on the contrary, the magnetic properties of the carbanion are diamagnetic.
  5. In various chemical reactions, the carbocation acts as an electrophile; conversely, in many chemical reactions, the carbanion acts as a nucleophile.
  6. The carbocation becomes more stable than the carbanion due to the presence of three donor methyl groups that donate electrons and thus greatly stabilize the positive charge.
  7. A carbocation is an electron deficient species; on the other hand, carbanion is an electron-rich species.
  8. The central carbon atom of the carbocation has 6 electrons in its outermost shell, while the central carbon atom of the carbanion has 8 electrons in its outermost shell.
  9. Carbocation can readily accept an electron pair from a nucleophile to produce a covalent bond, while carbanion normally donates an electron pair to an electrophile to produce a covalent bond.
Final Thoughts

The above discussion concludes that the carbocation comprises a carbon atom that has a positive charge and is an electron deficient species, while the carbanion comprises a carbon atom that has a negative charge and an electron rich species.

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