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Chemspider links: octanoic acid water

Researcher

Cuepil Choi

Objective

To determine if it is possible to distinguish water that has been absorbed into octanoic acid and water that remains in bulk. Exploring the possibility of using the NMR to examine this study

Procedure

To have an idea of where the peaks of bulk water and octanoic acid presented itself, an HNMR spectrum of both individual components were measured in NMR tubes with a larger NMR tube containing deuterated chloroform

Results

HNMR spectrum 1 - pure water
HNMR spectrum 2 - pure octanoic acid
HNMR spectrum 3 - water and octanoic acid at 25 C
HNMR spectrum 4 - water and octanoic acid at 35 C
HNMR spectrum 5 - water and octanoic acid at 45 C
HNMR spectrum 6 - water and octanoic acid cooled down to 26 C

Discussion

The inability to identify the water going into the octanoic acid may mean that doing the actual mixing in the NMR tube may be impossible. (verification needed)

Conclusion

The heating of the mixture showed that the most downfield proton from octanoic acid went from 12.33ppm in pure octanoic acid (HNMR spectrum 2) to 9.8ppm at 45 C (HNMR spectrum 5). The most downfield peak also showed signs of splitting, suggesting that two different populations may reside in the solution. However, the splitting is unlikely and the spectrum is unclear. The peaks return back to their original positions on the spectrum when the mixture is cooled down.

Log

2013-07-10

14:50 NMR tube filled with deionized water and capped with blue cap
14:52 NMR tube filled with octanoic acid and capped with yellow cap
14:53 NMR tube with water placed into larger tube containing deuterated chloroform
15:10-15:40 HNMR spectra were taken.