9 l=1 l=0 ml = -1 0 1 Valence shell 2s2 2p2 2s 2p E p x p y p z s n=2 First look at the normal electronic configuration of carbon: This is the reason why carbon is tetrahedral in many compounds
By hybridization of its valence atomic orbitals, carbon can bond in a variety of ways
sp3 hybridization
9 E Promote one 2s electron into the vacant p-orbital.
Combine (mix) all four orbitals to give four hybrid orbitals of equivalent energy:
sp3 hybridization
9 Each sp3 hybrid orbital has 25% “s” and 75% “p” character
Each sp3 hybrid orbital looks like a distorted dumbell:
sp3 Hybridization Animation
9 The best arrangement of orbitals is a tetrahedral geometry making angles of 109° Movie from Saunders General Chemistry CD-ROM
Tetrahedral bonding
10 Each sp3 hybrid orbital has one electron and can form a strong covalent bond with another atom, eg methane formation with four hydrogens:
Sigma () bonds
10 The H 1s and carbon sp3 hybrid orbitals are no longer separate entities and combine to form a sigma () bonding molecular orbital.
These bonds are 109.5° apart.
Sigma () bond formation
10 Movie from Saunders General Chemistry CD-ROM
Other representations
10 Ball and stick Space Filling
Other representations
10 Space Filling Potential Energy
Surface
C–C bond formation in Ethane
11 C H H H C H H H + C H H H C H H H sp 3 - sp 3 bond between carbons Sigma () bonds can be formed between two carbons by overlapping two sp3 hybrid orbitals.
Ethane
11 Ball and stick Space filling
Ethane
11 Ethane can spin about the C—C bond
There is nearly free rotation:
Propane
11 Propane is formed by covalent bonding to two
other carbons and eight hydrogens.
Ball and stick Space filling
Propane
11 Propane can rotate about both C—C bonds
Butane
7 Ball and stick Space filling 11 Butane is formed by covalent bonding between
four carbons and ten hydrogens.
Butane
7 11 Butane can rotate about all three C—C bonds
Bonding to other atoms
C H H H O H O H C H H H + sp 3 - sp 3 valence bond between carbon and oxygen giving an alcohol 12 Alcohols are formed between sp3 hybridised carbon and oxygen:
Bonding to other atoms
C H H H N H + H sp 3 - sp 3 valence bond between carbon and nitrogen giving an amine N H C H H H H 12 Amines are formed between sp3 hybridised carbon and nitrogen:
sp2 Hybridization Double bond formation
13 C C H H H H C O H H Ethene
(carbon sp2) Formaldehyde
(carbon, oxygen sp2) Carbon can form double bonds with itself and other heteroatoms.
This requires sp2 hybridization of its valence atomic orbitals.
Carbon is sp2 hybridized in:
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