Exp117-v.JPG


Objective

To monitor the synthesis of a Ugi adduct from propionaldehyde, methylamine, acetic acid and tert-butyl isocyanide by NMR spectroscopy.

Procedure

To a 2.0M solution of methylamine in methanol (500uL, 1 mmol) was added methanol-d4 (500uL) and propionaldehyde (72.15uL, 1 mmol) in an NMR tube. The imine formation was monitored by proton magnetic resonance spectroscopy. After 30min acetic acid (57.24uL, 1 mmol) and tert-butyl isocyanide (113.10uL, 1 mmol) was added to it. The reaction was further monitored.

Results


Methylamine (1.0M Solution in 1:1 CH3OH : CD3OD)
HNMR
Propionaldehyde (118A-F2)
HNMR (in CDCl3)
HNMR (in CD3OD)
tert-butyl isocyanide
H NMR
C NMR

Exp117A
t = 6min
t = 10min
t = 23min
t = 30min
Exp117B
t = 7min
t = 10min
t = 19h 45min

Discussion

Methanol reacts with propionaldehyde [1]. This is seen from the HNMR of distilled propanal in CDCl3 (a clean NMR) and an HNMR of the same distilled fraction in CD3OD. The results of this experiment were confirmed by obtaining HNMR of pure CD3OD to check the purity of the solvent and then the sample plus solvent. Samples for analysis in CDCl3 and CD3OD were added at the same time.
As the reference mentions, there may be acetalization and possibly other side reactions, aldol which may result in undesired products Therefore not only a conclusive peak assignment is difficult, but also following the reaction any further may not be fruitful. Therefore this experiment is aborted.

Conclusion

Experiment aborted

Log

2007-07-31

19:30 Added methylamine (500uL) to a solution of propionaldehyde in methanol, this is 117A
19:36 Obtained HNMR of 117A (t = 6min)
19:40 Obtained HNMR of 117A (t = 10min)
19:53 Obtained HNMR of 117A (t = 23min)
21:00 Obtained HNMR of 117A (t = 30min)
21:10 Added glacial acetic acid and tert-butyl isocyanide (117B)
21:17 Obtained HNMR of 117B (t = 7min)
21:20 Obtained HNMR of 117A (t = 10min)

2007-08-01

16:55 Obtained HNMR of 117B (t = 19h 45min)

References
1.Dakka and Goris; Catalysis Today Volume 117, Issues 1-3 265-270