chapter13_Part1

chapter13_Part1 - 13-13-1Nuclear Magnetic Nuclear Magnetic...

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Unformatted text preview: 13-13-1Nuclear Magnetic Nuclear Magnetic ResonanceResonanceChapter 13Chapter 1313-13-2Molecular SpectroscopyMolecular Spectroscopy◆Nuclear magnetic resonance (NMR) Nuclear magnetic resonance (NMR) spectroscopyspectroscopy::a spectroscopic technique that gives us information about the number and types of atoms in a molecule, for example, about the number and types of •hydrogen atoms using 1H-NMR spectroscopy•carbon atoms using 13C-NMR spectroscopy•phosphorus atoms using 31P-NMR spectroscopy13-13-3Nuclear Spin StatesNuclear Spin States◆An electron has a spin quantum number of 1/2 with allowed values of +1/2 and -1/2 •this spinning charge creates an associated magnetic field•in effect, an electron behaves as if it is a tiny bar magnet and has what is called a magnetic moment◆The same effect holds for certain atomic nuclei•any atomic nucleus that has an odd mass number, an odd atomic number, or both also has a spin and a resulting nuclear magnetic moment•the allowed nuclear spin states are determined by the spin quantum number, I, of the nucleus13-13-4Nuclear Spin StatesNuclear Spin States•a nucleus with spin quantum number Ihas 2I+ 1+ 1spin states; if I= 1/2, there are two allowed spin states•Table 13.1 gives the spin quantum numbers and allowed nuclear spin states for selected isotopes of elements common to organic compounds1H2H12C13C14N16O31P32SElementNuclear spinquantum number (I )Number ofspin states1/211/212312311/22113-13-5Nuclear Spins in BNuclear Spins in B•within a collection of 1H and 13C atoms, nuclear spins are completely random in orientation•when placed in a strong external magnetic field of strength B, however, interaction between nuclear spins and the applied magnetic field is quantized, with the result that only certain orientations of nuclear magnetic moments are allowed 13-13-6Nuclear Spins in BNuclear Spins in B•for 1H and 13C, only two orientations are allowed13-...
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This note was uploaded on 09/19/2011 for the course CHM 262 taught by Professor Staff during the Spring '08 term at Purdue.

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chapter13_Part1 - 13-13-1Nuclear Magnetic Nuclear Magnetic...

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