Submitted by azmanam / Butler University on Fri, 06/15/2012 - 09:19
My Notes

A simple coin-flipping game to help students understand the origin of spin/spin splitting in 1H NMR.

  • A quarter is taken as 'set of equivalent protons' with a 'chemical shift' value of $0.25.
  • One penny is flipped 2000 times.
    • If the penny lands heads, $0.01 is added to the value of the quarter; value = $0.26
    • If the penny lands tails, $0.01 is subtracted from the value of the quarter; value = $0.24
    • Keep a running tally of the occurance of each outcome
  • By flipping one penny 2000 times, students will see a 1000:1000 ratio of the two outcomes ($0.24, $0.26). This mimics the origin of a doublet from one neighboring proton with j-value $0.02
  • Students can 'flip' up to 9 pennies to simulate up to 9 neighboring protons all with j-value $0.02
  • Students can also 'flip' up to 4 nickels to simulate additional neighbors with a second j-value of $0.10
  • After 5 trials, a link appears to an explanation page tying together the concepts of flipping coins and NMR splitting/j-value

It's actually pretty hard to distil into a set of simple, easy-to-understand, easy-to-follow rules. The intervention would be better suited for actually physically bringing pennies into class and run the demonstration physically with students (which I plan to do). The web resource can be used in class to simulate the statistical mixture (especially if the class contains too few students to practically achieve a statistical distribution manually). The web resource can also be provided to students after they leave the class to reinforce the concept.

NMR Coin-Flip Game Preview Image

Learning Goals

A student should be able to explain the origin of NMR splitting, the meaning of a j-value, and predict the splitting pattern of simple systems with up to two different j-values.

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