BS132 Lecture 4

What is Hybridisation Theory?

• What might we expect from C?

• What might it hybridise to form?

• What happens to these hybrids?

• Might expect C (2p2) to form CH2 instead of CH4

• May hybridise 2s and 3 × 2p orbitals of C to give 4 degenerate sp3 orbitals

• 4 sp3 electrons of C become paired upon forming sigma bonds w/ 4 H atoms

What is the basis of Methane’s Shape?

2s non-directional, 3 × 2p orientated at 90 degrees

What is the Mathematical Mixing of Methane?

4 x sp3 orbitals at 109.5 degrees

What is Methane’s Shape?

Tetrahedral

What makes Methane energetically favourable?

Minimum repulsion between bonding electron pairs

What type of bonds are in the C=C Double Bond?

1 sigma and 1 pi

What happens to each C atom in the C=C Double Bond?

Sp2 hybridised so has 1 unhybridised p orbital

How are the sp orbitals in Ethane different to Ethene?

Tetrahedral around each sp3 hybridised atom

What happens to the unhybridised p orbitals in ethene?

Unhybridised p orbtials in ethene are orientated so they overlap to form a pi bond

How does the rigidity of Ethane compare to Ethene?

Isn’t as rigid, rotation around C=C isn’t possible due to pi bond

How does the strength of Alkenes compare to Alkanes?

C=C is stronger and shorter than C-C

What type of bonds are in C-C?

Sigma

What type of bonds are in C=C?

Pi and Sigma