Researcher

Evan Curtin

Objective

To determine the solubility of trans-cinnamic acid(1), salicylic acid(2), p-dimethylaminobenzaldehyde(3) and vanillin(4) in trifluoroethanol (TFE) by SAMS HNMR method.

Procedure

Results

SAMS Spreadsheet
The solubility in 2,2,2-trifluoroethanol is:
For trans-cinnamic acid: 0.159 M
For Salicylic acid: 0.081 M
For p-dimethylaminobenzaldehyde: 4.46 M
For vanillin: 2.029 M

Discussion

The solubilities of the solutes in ethanol are
For trans-cinnamic acid: 1.07 M
For Salicylic acid: 2.11 M
For p-dimethylaminobenzaldehyde: 0.630 M
For vanillin: 2.47 M

The solubilities of both carboxylic acids decrease significantly from ethanol to TFE. For p-dimethylaminobenzaldehyde, the solubility increases dramatically, while a slight decrease in solubility occurs for vanillin when comparing ethanol to TFE. The dramatic increase of solubility for dimethylaminobenzaldehyde is likely due to the acidity of the trifluoroethanol, which would increase the solubility of basic solutes.

TFE_solubility_11_8_2011.png

The predicted and measured solubilities are shown above for 10 compounds (predictions for salicylideneaniline cannot be made due to lack of enough data for the compound). The Abraham model does relatively poorly in predicting the solubilities of most compounds, possible exceptions being N-vanillylideneaniline and vanillin. It is not out of the question that those two values are a coincidence, considering the low correlation between most predicted and experimental values. Of particular interest are the predicted solubilities for 4-dimethylaminobenzaldehyde (which the model is predicting as miscible with TFE) and phenanthrene (the model is predicting 2.88 M, but previously determined solubility is very low). Further experiments should be done in order to validate/refute the solubility for phenanthrene, while it appears that more data is needed overall to improve the model for TFE.

All TFE solubilities are reported here .
The live solubility predictions are available from the live Solubility Book (it will take a few minutes to load - TFE is near the end of the entire document). Predicted and measured values in TFE on 2011-10-25.

Conclusion

Solubilities were determined for trans-cinnamic acid, salicylic acid, p-dimethylaminobenzaldehyde and vanillin in trifluoroethanol, but the predicted values at this time are not very accurate.

Log

2011-08-19

15:00 - Mixed 200-400 mg of each sample with trifluoroethanol.
15:13 - Added each sample to a 50C bath. Samples 3 and 4 dissolved in under a minute. Set 3 and 4 on counter at RT (24C).
15:35 - Removed 1 and 2 from bath (solid remained in each) and immediately filtered through a pipette with a kimwipe inside. Samples are now 1B and 2B
15:37 - Samples 3 and 4 formed precipitate. Filtered using pipette with a kimwipe.
15:43 - Samples 1B and 2B formed precipitate. Filtered.
16:10 - Took the supernatants, mixed with CDCl3 and tranferred to NMR tube.
16:45 - Took HNMR using varian 500MHz NMR.