Ch_322a_9.01

Ch_322a_9.01 - Chapter 9 Nuclear Magnetic Resonance and...

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Chapter 9 Nuclear Magnetic Resonance and Mass Spectroscopy: Tools for Structure Determination
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Spectroscopic Methods Matter interacts with radiation energy across a very wide spectral range from the ultraviolet-visible to the radiofrequency, but the modes of interaction differ greatly. M h ! uv-visible M * electronic transition M h ! rf in presence of a magnetic field M * nuclear spin transition The information obtained by nuclear magnetic resonance (nmr) spectroscopy provides the most detailed structural description of organic compounds of any methodology.
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Nuclear Magnetic Spectroscopy The nuclear particles ( neutrons and protons ) have the property of spin and a spin quantum number of 1/2. These particles contribute to the net spin quantum number for the nucleus ( I ). If I = 0, the nucleus has a net nuclear spin angular momentum and an associated nuclear magnetic moment (magnetic dipole moment). spinning charge with non-zero nuclear spin quantum number generates magnetic dipole moment In the presence of an external magnetic field , this nuclear magnetic moment can have more than one orientation relative to the external magnetic field. Each orientation has a different energy , and is a different nuclear spin state . The number of nuclear spin states ( N ) is given by N = 2 I + 1 where I is the nuclear spin quantum number.
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Some Empirical Rules for Values of I (1) Nuclei with even mass numbers and even atomic numbers have a nuclear spin quantum number of zero ( I = 0
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Ch_322a_9.01 - Chapter 9 Nuclear Magnetic Resonance and...

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