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Molecular Structure Experimental Methods Mechanisms

Experimental MethodsDiffraction. X-ray diffraction locates atoms by locatingthe electron density around an atom.The intensity of the effect is proportional to Z2.. Neutron diffraction locates atoms by locatingnuclei with a neutron beam. The effectis approximately proportional to Z.. Electron d

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Molecular Structure Experimental Methods Mechanisms

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    1. Molecular Structure Experimental Methods & Mechanisms Edward A. Mottel Department of Chemistry Rose-Hulman Institute of Technology

    3. Why are there three bands? Quadrapole splitting occurs if the sample is not in cubic symmetry. Is the structure pseudo tetrahedral or planar? VSEPR would put two unshared pairs of electrons on each iodine if each chlorine has an octet. The source generates gamma ray (high energy x-rays) with energies in the 100,000 eV range.Why are there three bands? Quadrapole splitting occurs if the sample is not in cubic symmetry. Is the structure pseudo tetrahedral or planar? VSEPR would put two unshared pairs of electrons on each iodine if each chlorine has an octet. The source generates gamma ray (high energy x-rays) with energies in the 100,000 eV range.

    4. Splitting indicates that the iodine atoms are not in equivalent environments. Also possible is a chloro-bromo bridged structure.Splitting indicates that the iodine atoms are not in equivalent environments. Also possible is a chloro-bromo bridged structure.

    6. Trigonal Bipyramidal Structural Dynamics

    9. red into the screen; yellow out of the screenred into the screen; yellow out of the screen

    10. Trigonal Bipyramidal Structural Dynamics

    11. Structural Dynamics Trigonal Bipyramidal

    12. red into the screen; yellow out of the screenred into the screen; yellow out of the screen

    13. 8/25/2012 Five Coordinate Structures

    14. Reactions Nucleophilic Displacement versus Elimination

    15. Reactions Nucleophilic Displacement versus Elimination

    16. Mechanisms

    17. Mechanisms

    19. Reactant Molecular Orbitals HOMO and LUMO Determination

    20. Mechanisms Symmetry, Energy & Chemical Considerations

    23. Case 1: HOMO of H2 overlapping the LUMO of C2H4: energetically favorable (carbon is more EN than hydrogen), chemically favorable (H2 bond breaks, C-C double bond breaks), symmetry forbidden (no net overlap). Case 2: HOMO of C2H4 overlapping the LUMO of H2: energetically unfavorable (carbon is more EN than hydrogen), chemically favorable (H2 bond breaks, C-C double bond breaks), symmetry forbidden (no net overlap). Hydrogenation of ethene does not occur without a catalyst to allow a symmetry allowed process. Case 1: HOMO of H2 overlapping the LUMO of C2H4: energetically favorable (carbon is more EN than hydrogen), chemically favorable (H2 bond breaks, C-C double bond breaks), symmetry forbidden (no net overlap). Case 2: HOMO of C2H4 overlapping the LUMO of H2: energetically unfavorable (carbon is more EN than hydrogen), chemically favorable (H2 bond breaks, C-C double bond breaks), symmetry forbidden (no net overlap). Hydrogenation of ethene does not occur without a catalyst to allow a symmetry allowed process.

    24. 8/25/2012 Catalysts The catalyst must take part in the reaction (and usually be in the rate determining step) be regenerated so that it doesn’t appear in the overall balanced reaction.

    25. Hydrogenation

    26. Hydrogenation

    27. Hydrogenation

    28. Hydrogenation

    29. Case 1: HOMO of B2Cl4 overlapping the LUMO of H2 : energetically favorable (hydrogen is more EN than boron), chemically favorable (H2 bond breaks, B-B bond breaks), symmetry forbidden (no net overlap). Case 2: HOMO of H2 overlapping the LUMO of B2Cl4 : energetically slightly unfavorable (boron is less EN than hydrogen), chemically favorable (H2 bond breaks, no change in B-B bond), symmetry allowed). However, each B-H bond formed would only contain 1 electron (1/2 bond order); the H2B2Cl4 formed would be very weak; homolytic cleavage of b-B bond would free up one electron for each boron to form more stable HBCl2.Case 1: HOMO of B2Cl4 overlapping the LUMO of H2 : energetically favorable (hydrogen is more EN than boron), chemically favorable (H2 bond breaks, B-B bond breaks), symmetry forbidden (no net overlap). Case 2: HOMO of H2 overlapping the LUMO of B2Cl4 : energetically slightly unfavorable (boron is less EN than hydrogen), chemically favorable (H2 bond breaks, no change in B-B bond), symmetry allowed). However, each B-H bond formed would only contain 1 electron (1/2 bond order); the H2B2Cl4 formed would be very weak; homolytic cleavage of b-B bond would free up one electron for each boron to form more stable HBCl2.

    30. Mechanisms Hydrogen and Oxygen

    31. 8/25/2012 Mechanisms Hydrogen and Oxygen

    32. Mechanisms Hydrogen and Oxygen

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