The NMR Spectrometer sample tube magnet RF transmitter detector recorder absorption magnet controller magnetic field Copyright2005 Pearson Prentice Hall,Inc. Chapter 13 11
Chapter 13 11 The NMR Spectrometer =>
circulution The NMR Graph H less shielded more shielded lower field(downfield) higher field(upfield) increasing magnetic field strength(Bo) Copyright 2005 Pearson Prentice Hall,Inc. Chapter 13
Chapter 13 12 The NMR Graph =>
CH3 H3C-Si-CH3 Tetramethylsilane CH3 TMS is added to the sample. ● Since silicon is less electronegative than carbon,TMS protons are highly shielded.Signal defined as zero. Organic protons absorb downfield(to the left)of the TMS signal. => Chapter 13 13
Chapter 13 13 Tetramethylsilane • TMS is added to the sample. • Since silicon is less electronegative than carbon, TMS protons are highly shielded. Signal defined as zero. • Organic protons absorb downfield (to the left) of the TMS signal. => Si CH3 CH3 CH3 H3C
circulution Chemical Shift Measured in parts per million. Ratio of shift downfield from TMS(Hz) to total spectrometer frequency(Hz). Same value for 60,100,or 300 MHz machine. Called the delta scale. => Chapter 13 14
Chapter 13 14 Chemical Shift • Measured in parts per million. • Ratio of shift downfield from TMS (Hz) to total spectrometer frequency (Hz). • Same value for 60, 100, or 300 MHz machine. • Called the delta scale. =>
circulition Delta Scale shift downfield from TMS(in Hz) chemical shift,.ppmδ= spectrometer frequency (in MHz) / 600Hz 480Hz 360Hz 240Hz 120Hz OHz 109 8765 4321 0 Ppm 8 ↑TMS 60 MHz 3000Hz2400Hz1800Hz1200Hz600Hz0Hz 109876 543210 Ppm ↑TMS 三> 300 MHz 15 Copyright 2005 Pearson Prentice Hall,Inc
Chapter 13 15 Delta Scale =>