Difference Between Carbocation and Carbanion

Main Difference

The main difference between carbocation and carbanion is that carbocation comprises a carbon atom having a positive charge, whereas carbanion comprises a carbon atom having a negative charge.

Carbocation vs. Carbanion

A carbocation is an ion having a carbon atom which is positively charged, while carbanion is an ion having a carbon atom which is negatively charged. The carbon atom of carbocation having a positive charge is sp2 hybridized, whereas carbon atom of carbanion having a negative charge is sp3 hybridized. The geometry of carbon atom in carbocation is trigonal planar; on the other hand, the geometry of carbon atom in carbanion is pyramidal. The magnetic properties of carbocation are paramagnetic; on the contrary, the magnetic properties of 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 carbanion due to the presence of three donor methyl groups which donate electrons and therefore greatly stabilize the positive charge. A carbocation is an electron-deficient specie; on the flip side, carbanion is an electron-rich specie. The central carbon atom of carbocation has 6 electrons in the outermost shell, while the central carbon atom of carbanion has 8 electrons in the outermost shell. Carbocation can greatly accept an electron pair from a nucleophile to produce a covalent bond, whereas carbanion normally donates an electron pair to an electrophile to produce a covalent bond.

Comparison Chart

CarbocationCarbanion
A carbocation is an ion having a central carbon atom which is positively chargedA carbanion is an ion having a central carbon atom which is negatively charged.
Hybridization
The carbon atom is sp2 hybridizedThe carbon atom is sp3 hybridized
Geometry
Trigonal planarPyramidal
Magnetic Properties
ParamagneticDiamagnetic
Reactions
Acts as an electrophileActs as a nucleophile
Stabilization
More stabilized due to the presence of three donor methyl groups which donate electrons and therefore greatly stabilize the positive chargeLess stabilized
No. of Electrons
An electron deficient specieAn electron rich specie
Electrons in Outermost Shell
6 electrons in the outermost shell8 electrons in the outermost shell
Accept/Donate an Electron Pair
Greatly accept an electron pair from a nucleophile to produce a covalent bondNormally donate an electron pair to an electrophile to produce a covalent bond

What is Carbocation?

The term carbocation is generally defined as an ion which central carbon atom is positively charged. Carbocation usually refers to the entire molecule, not just only represents the positively charged carbon atom and can have one or more positive charges in its central atom. A carbocation is normally unstable because due to the loss of electrons, the p orbitals of the central carbon atom are free. That is why carbocation is very less or often reactive with other ions, but this favors the reaction to occur between carbocation and a nucleophile because in various chemical reactions the carbocation acts as an electrophile. But carbocation is more stabilized than carbanion due to the presence of three donor methyl groups which donate electrons and therefore greatly stabilize the positive charge. The magnetic properties of carbocation are paramagnetic because of incomplete electron pairing. Characteristically, carbon atom of carbocation having a positive charge is sp2 hybridized because a carbon atom can have just only three bonds around its structure. The geometry of carbon atom in carbocation is trigonal planar. The central carbon atom of 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 are attached.

Types of Carbocation

  • Methyl Carbocation
  • Primary Carbocation
  • Secondary Carbocation
  • Tertiary Carbocation

What is Carbanion?

The term carbanion is usually defined as an ion which central carbon atom is negatively charged. The central carbon atom having the negative charge is sp3 hybridized. The geometry of carbon atom in carbanion is pyramidal just except for benzyl carbanion. The outermost shell of 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 carbanion are diamagnetic because of the completion of electron combination. The smallest considered carbanion is “methide ion” which is formed by methane from the loss of a proton. Four major 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 which is positively charged, while carbanion having a carbon atom which is negatively charged.
  2. The carbon atom of carbocation is sp2 hybridized, whereas carbon atom of carbanion which is negatively charged is sp3
  3. The structure of carbon atom in a carbocation is trigonal planar; on the other hand, the geometry or structure of carbon atom in carbanion is pyramidal.
  4. The attractive properties of carbocation are paramagnetic; on the contrary, the magnetic properties of carbanion are diamagnetic.
  5. In various chemical reactions, the carbocation performs as an electrophile; conversely, in many chemical reactions, the carbanion acts as a nucleophile.
  6. Carbocation becomes more stable than carbanion due to the presence of three donor methyl groups which donate electrons and therefore greatly stabilize the positive charge.
  7. A carbocation is an electron-deficient specie; on the flip side, carbanion is an electron rich-specie.
  8. The central carbon atom of carbocation has 6 electrons in its outermost shell, while the central carbon atom of carbanion has 8 electrons in its outermost shell.
  9. Carbocation can readily accept an electron pair from a nucleophile to produce a covalent bond, whereas carbanion normally donates an electron pair to an electrophile to produce a covalent bond.

Conclusion

Above discussion concludes that carbocation comprises a carbon atom having a positive charge and it is an electron-deficient specie, whereas carbanion comprises a carbon atom having a negative charge and an electron-rich specie.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss

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