How can we construct

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How can we construct the Molecular Orbitals for
Acetylene?
Let us break the problem in to parts.
2
px
px
py
py
s
p
2p
s
pz
pz
p
s
2s
N2
B.O. 3
diamagnetic
s
3
px
px
py
py
s
p
2p
p
pz
pz
s
s
2s
C2-2
B.O. 3
diamagnetic
s
Isoelectronic with N2
4
s
p
p
s
s
s
s
Make two combinations of H 1s orbitals. One
and one -
C2-2
s
5
s
p
p
s
p
p
s
s
s
s
Make two combinations of H 1s orbitals. One
and one -
C2-2
s
s
6
Mainly p
average to give sp hybrids
Make two combinations of H 1s orbitals. One
and one -
Mainly s
C2-2
7


sp hybrid
-

sp hybrid
8
H s - C sp sigma bond
C sp - C sp sigma bond
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From your textbook
sp hybrids
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sp2 hybrids
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H2
H1
H4
H3
Y1 H1 H2 H3 H4
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H2
H1
H4
H3
Y2 H1 H2 - H3 - H4
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Y1 H1 H2 H3 H4 C 2s
Y2 H1 H2 - H3 - H4 C 2pz
Y3 H1 - H2 H3 - H4 C 2px
Y4 H1 - H2 - H3 H4 C 2py
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px
py
C
Y1, Y2, Y3, Y4,
pz
H s LCAOs
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C
Individual H s orbitals
4 equal C sp3 - H s bonds
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Delocalized Model Hybrid Orbital Model
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