# Alkynes: Properties

## Alkynes: Molecular Orbital Model

Fig.1
MO Diagram of the C-C bond of acetylene

(MO theory) combines atomic or hybrid orbitals (AOs) to molecular orbitals (MOs). The $sp$ hybrid orbitals combine and form a bonding σ orbital and an antibonding σ* orbital. The four p atomic orbitals form two π and two π* molecular orbitals. The energy sequence from the lowest to the highest MO is σ < π(y) = π(z) < π(y)* = π(z)* < σ*. Overall, six electrons are available to occupy the molecular orbitals, e.g. only bonding orbitals are filled.

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