Scalar_coupling_10 - Origin of Scalar Couplings BCMB/CHEM...

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Origin of Scalar Couplings BCMB/CHEM 8190
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Traditional View of Scalar Coupling Dipole Model: Two equal intensity lines from each interaction for each spin R 1 H C 1 H A 1 H B C B A 1 H Reasons to understand couplings: - magnetization transfer (COSY, HSQC) - structural information Problem: dipolar interactions average to zero in solution J BC J AB Measurement: directly as above, 2D J-resolved, intensity based
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Multiple sets of spins Multiplet structure: as many as n2 (n-1) lines in non- equivalent first order sets, 2 2 X 3 = 12 lines for previous example Unequal intensities in equivalent cases; proton next to a methylene, has states αα , αβ , βα , ββ ; a 1:2:1 triplet αα αβ , βα ββ
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The Origin of Scalar Coupling Constants B 0 μ A μ B r θ μ B μ A e - e - μ B μ A e - e - Low E High E Mechanism: not through space, but Fermi contact E (3cos 2 θ - 1) / r 3 E s A x s B J
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Fermi-Contact Expression for Scalar Coupling • Expression comes from second order perturbation treatment of spin contribution to electronic energy • E = (4g
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This note was uploaded on 11/07/2011 for the course CHEM 8853R taught by Professor Gelbaum during the Fall '11 term at Georgia Institute of Technology.

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Scalar_coupling_10 - Origin of Scalar Couplings BCMB/CHEM...

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