Protons in a molecule more shielded. absorb at a higher field H C-0: less shielded. H absorbs at a lower field Copyright2010 Pearson Prentice Hall,Inc. Protons in different chemical environments are shielded by different amounts. The hydroxyl proton is not shielded as much as the methyl protons so the hydroxyl proton absorbs at a lower field than the methyl protons. We say that the proton is deshielded somewhat by the presence of the electronegative oxygen atom. Chapter 13 11
Chapter 13 11 Protons in a Molecule • Protons in different chemical environments are shielded by different amounts. • The hydroxyl proton is not shielded as much as the methyl protons so the hydroxyl proton absorbs at a lower field than the methyl protons. • We say that the proton is deshielded somewhat by the presence of the electronegative oxygen atom
NMR Signals The number of signals shows how many different kinds of protons are present. The location of the signals shows how shielded or deshielded the proton is. The intensity of the signal shows the number of protons of that type. Signal splitting shows the number of protons on adjacent atoms. Chapter 13 12
Chapter 13 12 NMR Signals • The number of signals shows how many different kinds of protons are present. • The location of the signals shows how shielded or deshielded the proton is. • The intensity of the signal shows the number of protons of that type. • Signal splitting shows the number of protons on adjacent atoms
The NMR Spectrometer sample tube RF transmitter magnet detector printer absorption magnet Bo controller magnetic field Copyright2010 Pearson Prentice Hall,Inc. Chapter 13 13
Chapter 13 13 The NMR Spectrometer
NMR Instrument Copyright 2010 Pearson Prentice Hall,Inc Chapter 13 14
Chapter 13 14 NMR Instrument
The NMR Graph downfield upfield more deshielded more shielded lower field (downfield) higher field(upfield) increasing magnetic field strength (Bo)- Copyright010 Pearson Prentice Hall,Inc The more shielded methyl protons appear toward the right of the spectrum (higher field);the less shielded hydroxyl proton appears toward the left(lower field). Chapter 13 15
Chapter 13 15 The NMR Graph • The more shielded methyl protons appear toward the right of the spectrum (higher field); the less shielded hydroxyl proton appears toward the left (lower field). downfield upfield