文档介绍：Proton Nuclear ic Resonance Proton Nuclear ic Resonance Spectrometry ( Spectrometry ( 1 1 H NMR) H NMR) Typical Typical 1 1 H NMR Spectra H NMR Spectra CH 2 CH 2CH 2 CH 3 O C CO C CH 3H H sixtet sixtet quintet quintet Parameters: chemical shift area of peaks coupling constant Introduction Introduction ic Properties of Nuclei nuclear ic moment ? spin quantum number I ELEMENT # Protons # Neutrons I (Spin Quantum Number) 1H 1 0 1/2 2H 1 1 1 3H 1 2 1/2 4He 2 2 0 3He 2 1 1/2 6Li 3 3 1 7Li 3 4 3/2 10B 5 5 3 11B 5 6 3/2 12C 6 6 0 13C 6 7 1/2 14N 7 7 1 15N 7 8 1/2 Even mass: # protons & # Neutrons Both Even : I=0 ( 4 He, 12 C …) No spin # Protons & # Neutrons Both Odd : I=1, 2, …. (Integer) Odd mass: # protons odd & # Neutrons Even : I=1/2, 3/2, ... (Half-integer) # protons even & # Neutrons odd : I=1/2, 3/2, ... (Half-integer) 1 H and 13C both have spin = ± 1/2 1 H is 99% at natural abundance 13 C is % at natural abundance The nuclei that are most useful anic chemists are: ++ + + + The distribution of The distribution of nuclear spins is nuclear spins is random random in the in the absence absence of an of an external ic field. external ic field. ++ + + + An external ic field An external ic field causes nuclear ic causes nuclear ic moments to align moments to align parallel parallel and and antiparallel antiparallel to applied to applied field. field. H H 0 0 Directional Quantization Directional Quantization If a nucleus with ic Moment ???? is placed in a ic field B B 0. 0. The direction of spinning nuclei is quantized and described with m m ( ( ic quantum number ic quantum number ) )B B 0 0???? m m is the ic or directional quantum number it can take values: m m = I I , I I -1 -1 , …. , - -I I There are then 2 2I I + 1 + 1 orientations in the field 1 H, 13 C 2 directions m m = + + ? ?m m