Lecture 3 - MO Benzene Butadiene C 4 H 6 Alternating single...

Info icon This preview shows pages 1–28. Sign up to view the full content.

View Full Document Right Arrow Icon
Theories of Chemical Bonding –  Lecture 3
Image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Review Molecular Orbitals MOs transcend the entire molecule sigma and pi MOs Bond order
Image of page 2
MOs can explain observed physical  properties e.g. bond energies, bond lengths, magnetic properties
Image of page 3

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
π 2p σ 2p π 2p σ * 2p σ * 2s σ 2s antibonding bonding
Image of page 4
π 2p σ 2p π 2p σ * 2p σ * 2s σ 2s N 2 , BO = 3
Image of page 5

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
π 2p σ 2p π 2p σ * 2p σ * 2s σ 2s N 2 + , BO = 2.5
Image of page 6
N 2 N 2 + bond order 3 2.5 bond energy (kJ/mol) 945 841 bond length (nm) 0.110 0.112
Image of page 7

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
π 2p π 2p σ * 2p σ * 2s σ 2s σ 2p O 2 , BO = 2
Image of page 8
π 2p σ * 2p σ * 2s σ 2s σ 2p π 2p O 2 + , BO = 2.5
Image of page 9

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
O 2 O 2 + bond order 2 2.5 bond energy (kJ/mol) 498 623 bond length (nm) .121 .112
Image of page 10
Molecule BO Bond Bond Energy Length (kJ/mol) (nm) F 2 1 154 .144 B 2 1 290 .16 O 2 2 495 .121 C 2 2 620 .131 N 2 3 942 .110
Image of page 11

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Remember NO? N = O or N = O : : ?? : : .. .. . .
Image of page 12
2p 2p 2s 2s σ * 2s σ 2s π 2p π 2p σ 2p σ * 2p N O NO
Image of page 13

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Magnetism paramagnetic - unpaired electrons are attracted to the magnetic field diamagnetic - paired electrons are repelled by the magnetic field
Image of page 14
π 2p σ 2p π 2p σ * 2p σ * 2s σ 2s O 2 , BO = 2 Unpaired! (Hund’s Rule)
Image of page 15

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 16
Benzene, C 6 H 6 C C C C C C H H H H H H
Image of page 17

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Benzene - resonant forms = = Kekulé structures
Image of page 18
Image of page 19

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
Image of page 20
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: MO Benzene Butadiene, C 4 H 6 Alternating single and double bonds “conjugation” σ-bonds π-bonds Carbon Dioxide Filled Empty Filled Highest Occupied MO (HOMO) Lowest Unoccupied MO (LUMO) Conjugation may lead to colour π π Unconjugated System Large energy gap HOMO LUMO π π Conjugated System Smaller energy gap HOMO LUMO h υ h υ UV absorption (VIS absorption, coloured!) β-carotene chlorophyll xanthin Band Theory of Solids Band Theory of Solids HOMO LUMO Metals conduct electricity… LUMO HOMO Negative potential raises the energy of the LUMO LUMO HOMO HOMO Lead Diamond Summary ● MO’s are delocalized ● no need for resonance forms ● can predict bond order ● correlations with bond length, bond energy, magnetic and optical properties...
View Full Document

{[ snackBarMessage ]}

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern