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Chemspider links: octanoic acid water

Researcher

Cuepil Choi

Objective

To examine how octanoic acid saturated with water looks on the HNMR spectrum and water saturated with octanoic acid. Follow up of CRSEXP004

Procedure

Approximately 1:1 volume of octanoic acid and water were pipetted into a test tube and vortexed. The solution was left to settle for about 3 hrs and the individual layers were filtered through a kimtech wipe inside a small pasteur pipette and the filtrate was put into NMR tubes. HNMR spectra were taken at 26.5 C with deuterated chloroform in an outer tube.

Results

HNMR spectrum 1 - octanoic acid saturated with water
HNMR spectrum 2 - water saturated with octanoic acid

Discussion

The shifts may mean that we might be able to observe the amount of water in the octanoic acid with the position of the shift. It is also puzzling why the peak did not shift down to 10 ppm as we observed when we mixed the octanoic acid with water in CRSEXP004.

Conclusion

There was no peak at 4.8 ppm in HNMR spectrum 1 as we observed when we mixed the octanoic acid and water in the NMR tube. The most downfield proton that was observed at 12.33ppm in pure octanoic acid moved down to 11ppm. HNMR spectrum 2 showed a peak at 4.77. This peak representing water saturated with octanoic acid is significantly shifted from its normal 4.8ppm peak when it is pure. An impurity was labeled at 1.57ppm which was labeled as acetone.

Log

2013-07-11

12:54 octanoic acid pipetted into test tube
12:59 water pipetted into test tube, water sank to bottom and two layers formed. approximately 1:1 ratio by volume
13:00 vortexed for approximately 20 seconds
14:50 acid layer taken from top and filtered through a kimtech wipe filter in a small pasteur pipette.
15:01 air blown through pipette to accelerate filtering. Filtered acid pipetted into NMR tube
15:30 water layer taken from top and filtered through kimtech wipe filter in a small pasteur pipette
15:41 filtered water put into NMR tube
17:05 HNMR spectrum 1 taken of NMR tube with octanoic acid saturated with water at 26.5 C with outer tube of deuterated chloroform. TMS peak set to 0 ppm
17:10 HNMR spectrum 2 taken of NMR tube with water saturated with octanoic acid at 26.5 C with outer tube of deuterated chloroform. TMS peak set to 0 ppm