Discuss the concept of hybridisation. What are its different types in a carbon atom?
b) What is the type of hybridisation of carbon atoms marked with star?
(i) `overset(**)(C)H_(2)=CH-overset(O)overset(**||)(C)-O-H` (ii) `CH_(3)-overset(**)(C)H_(2)-OH`
(iii) `CH_(3)-CH_(2)-overset(O)overset(||)(C^(**))-H` (iv) `overset(**)(C)H_(3)-CH=CH-CH_(3)`
(v) `CH_(3)-overset(**)(C)-=CH`

Explanation

Hybridisation: It can be defined as the process of intermixing of the orbitals of slightly different energy or of same energy to produce entirely new orbitals of equivalent energy, identical shape and symmetrical disposed in plane. New orbitals formed are called hybrid orbitals.
Only the orbitals of an isolated single atom can undergo hybridisation. The hybrid orbitals generated are equal in number to that of the pure atomic orbitals which mix up.
Hybrid orbitals do not make `pi`, pi-bonds. If there are `pi`-bonds. If there are `pi`-bonds, equal number of atomic orbitals must be left unhydrated for `pi`-bonding.
Like atomic orbitals, hybrid orbitals cannot have more than two electrons of opposite spins.
Types of hybridisation in carbon atoms.
a) i) Diagonal or sp-hybridisation: All compounds of carbon containing C`-=`C triple bond like ethyne `(C_(2)H_(2))`.
ii) Trigonal or `sp^(2)` hybridisation All compounds of carbon containing C=C (double bond) like ethene `(C_(2)H_(4))`.
Tetrahedral or `sp^(3)` hybridsation. All compounds of carbon containing C-C single bonds only like ethane `(C_(2)H_(6)`
b) (i) `underset((3s))underset(sp^(2))(overset(**)CH_(2))=underset((3s))underset(sp^(2))(CH-overset(O)overset(||)(C^(**))-O-)H`
(ii) `underset((4sigma))underset(sp^(3))(CH_(3)overset(**)(C)H_(2)OH)` (ii) `CH_(3)-CH_(2)-underset((3sigma))underset(sp^(2))overset(O)overset(||)(C^(**))-H`
(iv) `underset((4sigma))underset(sp^(3))overset(**)(CH_(3))-CH=CH-CH_(3)` (v) `underset((2sigma))underset(sp)(CH_(3)-overset(**)(C)-=CH)`