Nuclear Magnetic Resonance Spectroscopy

Nuclear Magnetic Resonance Spectroscopy

1. Definition: use of radiofrequency pulses (type of electromagnetic radiation) to generate quantized energy in molecules (from spinning nuclei)

   • I = spinning nuclei ; I > 0 to generate magnetic field
   • Measured in ppm
     • ppm = frequency of signal (Hz) / applied spectrometer frequency (MHz)

2. Interpreting 1^H NMR Spectra

   • Number of Different Types of Protons
     • Count # of signal groups
   • Relative number of protons contributing to signal per group (integration)
     • Height of each signal group affects total relative signal intensity (taller = higher amount of protons)
   • Signal positions on x-axis (chemical shift)
     • Study chemical shifts table to determine what a signal group's location means
       • Functional groups
       • Specific types of bonds
     • NOTE: Heavily affected by surrounding electron density (inducing own magnetic field) => less impact from applied magnetic field
       • Local diamagnetic shielding
       • Smaller electron density = deshielding
         • From electronegative atom shifting electron density towards them and away from protons
   • Patterns within signal groups (spin-spin coupling)