Problems
16.1 Calculate the resonance frequency of a proton in a magnetic field of (a) 7 T and (b) 20 T.
16.2 Calculate the resonance frequency of a^14 N nucleus in a magnetic field of (a) 20 T and
(b) 9 T.
16.3 If the mass of a proton was only 4× 10 −^29 kg, what would nuclear magneton become?
16.4 Explain what usually causes a large chemical shift.
16.5 Explain what a shielding constant is.
16.6 Why are high magnetic fields normally useful in NMR experiments?
16.7 For two coupled protons, what is the value of the lowest-energy state in the presence of
a magnetic field?
16.8 How many lines are present when a proton interacts with four protons?
16.9 What type of magnetic field is used in an MRI experiment?
16.10 When a spin pulse is applied to the sample with the direction of its magnetic field per-
pendicular to the external magnetic field, what happens to the spins?
16.11 How many lines are present when a proton interacts with a^14 N nucleus?
16.12 How many lines are present when a proton interacts with another proton?
16.13 Describe the expected two-dimensional NMR spectrum of methionine.
16.14 Predict what the two-dimensional NMR would be for the newly found amino acid
“carbonine 2”, which has the following structure:
16.15 What is a spin echo in an NMR experiment?
HCH 2CH 3 CH 2CH 3Cα COOCH 3CH CHND 2CHAPTER 16 MAGNETIC RESONANCE 371
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