ORGANIC CHEMISTRY Chapter 9 9.3 Chemical shift(化学位移)Peak PoSition in an Nmr Spectrum o The frequency of a signal is known as its chemical shift o The chemical shift in absolute terms is defined by the frequency of the resonance expressed with reference to a standard compound which is defined to be at 0 ppm. The scale is made more manageable by expressing it in parts per million (ppm) and is indepedent of the spectrometer frequency Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 9.3C Chemical Shift(化学位移). Peak Position in an NMR Spectrum The frequency of a signal is known as its chemical shift. The chemical shift in absolute terms is defined by the frequency of the resonance expressed with reference to a standard compound which is defined to be at 0 ppm. The scale is made more manageable by expressing it in parts per million (ppm) and is indepedent of the spectrometer frequency
ORGANIC CHEMISTRY Chapter 9 frequency of signal -frequency of reference 10 spectrometer frequency Unshield Shield Downfield Upfield 1098 ppm Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 frequency of signal − frequency of reference spectrometer frequency × 10-6 δ = Unshield Shield Downfield Upfield 10 9 8 7 6 5 4 3 2 1 0 ppm
ORGANIC CHEMISTRY Chapter 9 6H CH Htb Si(Ch3) (O)H H(b) 1.5 Tetramethylsilane CH 1.0 CTMS) (ay TMS 8 5 4 0 o The spectrum is measured on a delta(8)scale in units of ppm 9 Lower frequency is to the left in the spectrum; these absorptions are said to be downfield 9 Higher frequency is to the right in the spectrum: these absorptions are said to be upfield o The number of signals in the spectrum corresponds to the number of unique sets of protons Department of Chemistry, Xiamen University
ORGANIC CHEMISTRY Department of Chemistry, Xiamen University Chapter 9 The spectrum is measured on a delta (δ) scale in units of ppm Lower frequency is to the left in the spectrum; these absorptions are said to be downfield Higher frequency is to the right in the spectrum: these absorptions are said to be upfield The number of signals in the spectrum corresponds to the number of unique sets of protons