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Topics part 1

Topics part 1. Imagine the 1 H NMR spectrum of a compound recorded on a 300 MHz NMR spectrometer and on a 600 MHz NMR spectrometer. At 600 MHz, the chemical shifts and coupling constants are larger if measured in Hz, (2) the chemical shifts are larger if measured in ppm,

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Topics part 1

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  1. Topics part 1 • Imagine the 1H NMR spectrum of a compound recorded on a 300 MHz NMR spectrometer and on a 600 MHz NMR spectrometer. At 600 MHz, • the chemical shifts and coupling constants are larger if measured in Hz, • (2) the chemical shifts are larger if measured in ppm, • (3) the chemical shifts remain the same if measured in ppm and the coupling • constants remain the same if measured in Hz.

  2. B0?

  3. J at 0 K? 3-spin system NMR experiment

  4. Michael Palin travelled straight from the North Pole to the South Pole via Europe and Africa. Depict his travel route from the viewpoint of an observer suspended in outer space at the Hubbell telescope by tracing simultaneously his north-south movement and his movement due to the rotation of the earth around its axis. In the rotating frame of the earth, what is the approximate position of the axis he precessed around on his way south? • The axis intersected the equator in America and Singapore. • (2) The axis intersected the equator in Africa and the Pacific Ocean. • (3) The axis was the vector sum of the precession around the axis of earth rotation and • the axis defining his precession from north to south.

  5. The Larmor frequency is given by w0 = -gB0. Some nuclear spins have positive gyromagnetic ratio (e.g. 1H) and some have negative gyromagnetic ratio (e.g. 15N). What does a negative frequency imply? • An electromagnetic wave travelling in the other direction. • (2) Opposite sense of precession. • (3) The concept is artificial as the magnetic field component of an • electromagnetic wave always oscillates in a plane. • (4) The sign indicates the position of the NMR signal relative to TMS.

  6. A bicycle rider has a reflector in the back wheel. Viewed from behind at night, the reflected light appears to travel up and down as the wheel rotates. Plotting the up- and down-movement of the light as a function of time yields a function f(t) that, depending on the sense of rotation and the starting point, can be described by • sin(wt) • (2) cos(wt) • (3) exp(-iwt) • (4) exp(iwt) • (5) sin(wt + f) • (6) exp(-iwt - if) • (7) all of the above • (8) none of the above

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