- Carbon bearing positive charge ( C+).
- They have 6 e– s in its vanalce shell. i.e, incomplete octet state.
- They have tendency to accept a pair of electrons, thus they act as electrophile.
- They are from by the heterolytic cleavage.
- C – atom is in SP2 hybridized state.
- The geometry of carbocation is planar.
- They may be primary, secondary and tertiary.
- stability Order : 30 > 20 > 10 > CH3+
- Reactivity order : 30 < 20 < 10 < CH3+
Note: The lesser the stability the greater is its reactivity.
Carbocations are generated from :
- From Halides using a strongly ionizing solvent or by adding Lewis acid.
- Alcohol on treated with acid.
- Amines are treated with nitrous acid.
- Protonation of alkene.
- Reaction of aldehyde and ketone with acid catalyst.
Measurement of a carbocation :
- The formation of carbocations in hyper acid media allows us to study the different properties of carbocations.
- The solvent can be eliminated completely by making the use of mass spectrometry.
Three main factors that help to stabilize carbocations :
- Neighbouring carbon atoms
- Neighbouring atom with lone pair of electrons
- neighbouring carbon – carbon multiple bonds.
The energy difference between primary, secondary, and tertiary carbocations is approximately 11-15 Kcal mol-1 .
If electrons were money then carbocation would be the beggers in organic chemistry.
Carbocations are reactive intermediates in many organic chemical reactions. the idea was first proposed by Julius Stieglitz in 1899.
Professor George Olah created a method to prepare long-lived carbocations in high concentration which made it possible to study their structure, stability, and reactions by using spectroscopic methods.