13 - NOE - The Nuclear Overhauser Effect Read section 5.4...

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1 The Nuclear Overhauser Effect Read section 5.4 The nuclear Overhauser effect (NOE) The NOE is the fractional change in intensity of one NMR line when another resonance is irradiated. The NOE is due to dipolar interactions between different nuclei and is correlated with the inverse sixth power of the internuclear distance. No bond is required between the nuclei (through-space effect). r
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2 NOE is thus: where I is the observed intensity with irradiation of spin S and I 0 is the intensity without irradiation. Multiply by 100 to get percent. S is the perturbed (source) spin and I is the enhanced or interesting spin. 0 0 I I I = η Steady state NOEs (usually collected as a pair of experiments and shown as a difference spectrum).
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3 NOEs in a two spin system (possible transitions) All of the W 1 transitions are single quantum and equal for each spin (I and S differ by their difference in chemical shift). The spectrum without irradiation would look like a) The dipolar interactions do not produce an observable splitting the total spin population is 4 Saturate S and you have equal populations The W 0 pathway is dominant The W 2 pathway is dominant
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4 A closer look at the population differences: The population
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This note was uploaded on 10/08/2009 for the course CHEM 439 taught by Professor Falzone,c during the Spring '08 term at Penn State.

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13 - NOE - The Nuclear Overhauser Effect Read section 5.4...

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