(i) Carbanion Formation : It is formed by means of heterolytic fission. The organic compounds containing active hydrogen atom reacts with base to form carbanion.
e.g.,
Stability:
There are three types of carbanion:
Primary, Secondary and Tertiary carbanion. Greater the +I effect, lesser will be the stability of carbanion. The relative order of stability among carbanions is
Geometry : In carbanion, carbon atom is sp3 hybridised. Its geometry is pyramidal.
(ii) Carbene :
Formation : Carbene is formed by the photolysis of the aliphatic diazo compounds or ketenes.
of carbenes are highly reactive but the singlet state is generally considered as less stable.
Geometry: In singlet state of carbene, carbon is sp2 hybridised. The bond angle is 120° and geometry is trigonal planar. In triplet state of carbene, carbon is sp hybridised. The bond angle is 180° and geometry is linear.
(iii) Free Radicals Formation: Free radicals are formed by means of homolytic fission
Stability: Free radicals are classified as primary, secondary and tertiary. Tertiary alkyl free radical is most stable due to greater +I effect.
Greater the +I effect, greater will be the stability of free radical.
Geometry: The carbon in alkyl free radicals is sp2 hybridised. The geometry is trigonal planar and bond angle is 120°.
