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.
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.