The stability of carbocations is influenced by several factors, primarily the degree of substitution and the availability of hyper-conjugative hydrogens.
Stability Factors: Tertiary carbocations (three alkyl groups attached) are more stable than secondary (two alkyl groups), which in turn are more stable than primary (one alkyl group) and methyl (no alkyl groups). The order of stability due to hyperconjugation and inductive effects is:
Tertiary > Secondary > Primary > Methyl.
Correct Order: The correct stability order of the carbocations is:
(CH3)3C+ > (CH3)2CH+ > CH3–CH2+ > CH3+.
Thus, the correct order of stability for the given carbocations is:
The metal-carbon bond possesses both the σ and π character in a metal carbonyl. The synergic effect produced by the metal-ligand bond strengthens the bond between the carbonyl molecule and the metal. The types of bonding that exist in metal carbonyls are as follows:
Structure of Metal Carbonyls:
Due to the donation of electrons by the carbonyl molecules to the vacant orbitals of the metal, a metal-carbon σ bond is formed.
Due to the donation of a pair of electrons from a filled d orbital metal into the vacant anti bonding π orbital of carbonyl ligand, a metal-carbon π bond is formed.
Stability of Coordination Compounds:
They are found to dissociate in various solutions. The stability of a coordination compound in a solution mainly depends on the degree of association between the two species involved in the state of equilibrium. For the formation of the compound quantitatively the stability of any complex is given by the magnitude of the equilibrium constant. For instance,
