Objective

Monitor the formation of an aromatic imine by HMR and CMR in CDCl3

Steps

  1. Make up separate 1 mL of 1M solutions of piperonal and 5-methylfurfurylamine in CDCl3.
  2. Take HMRs and CMRs of the aldehyde and amine. Use 5 sec relaxation time and acquire for about 15 mins for the CMR. This should be good enough based on James' results at 1M in methanol.
  3. Combine the two solutions into a 1 dram vial and shake vigorously then transfer to an NMR tube.
  4. Take HMR at 5, 10 and 20 minutes after mixing.
  5. Take CMR at 25 min after mixing.
  6. Take HMR at 40 min after mixing.
  7. Take CMR at 45 min after mixing.
  8. Take HMR at 80 mins after mixing.
  9. Take CMR at 85 mins after mixing.
  10. Continue to take NMRs after interval doubling until no more change is observed.

Variations

  1. Use methanol-d4 instead of CDCl3.
  2. Use phenylacetaldehyde instead of piperonal to see the difference with an aliphatic aldehyde. We expect the aromatic aldehyde to be slower.
  3. Use 30 and 60 sec relaxation times to approach quantitative peak heights in CMR.