Objective


To study the effect of phenylacetic acid on the solubility of the Ugi product UCExp176C in benzene.

Procedure

A 1.1M solution of phenylacetic acid was made-up in benzene in a 5mL volumetric flask by dissolving 749mg of the acid. Using this as a stock solution (157-1A) serial dilution was performed as shown in the table below to obtain dilute solutions .
To the dilute solution in benzene Ugi product UCExp176C was added until no more of the solute dissolve upon vortexing. These solutions were placed in a temperature controlled bath at 40C for 12h. Then the temperature was reduced to 25C, with the samples left to equlibrate for another 2h.
Supernatants from each sample vial was separated and HNMRs were obtained. Using SAMS methodology solubility of the Ugi product was obtained.

Results

Spreadsheet ONSCExp157
ONSCExp157plot-i.jpg
Figure 1 Plot of the Ugi product 176C solubility in benzene as a function of phenylacetic acid concentration.


Discussion

There appears a linear relation between solubility of the Ugi product beyond 0.02M phenylacetic acid concentration. The equation of this linear line is y = 0.2108x + 0.0362 with an R^2 = 0.9957. Phenylacetic acid concentration at 0.18M concentration of the Ugi product UC176C was calculated at 0.7M.
Note: * Represents the solubility of the Ugi product UC176C in its 4-component reaction mixture.

So far the following information is known about the the Ugi product 176C from previous experiments
a) Rate constant for its formation - K= 6.2x10-3M-1 min-1 and its solubility in the reaction mixture was estimated at 0.18M (UCExp249)
b) Solubility in benzene - 0.03M (Solubility database)
c) Its solubility remained unaffected in the presence of phenanthrene-9-carboxaldehyde and furfurylamine. (Exp144)
d) Concentration of phenylacetic acid in saturated solution of Ugi product UC176C was 0.7M
d) Imminium concentration in saturated solution of Ugi product UC176C was 0.8M


Conclusion

Log

2009-12-29
10:15 Switched on the heater on the water/glycol bath and set it to 40C. Parafilmed the vials.
10:20 Weighed out phenylacetic acid (749mg, 5.5mmol) in a 5mL volumetric flask.
10:50 Added a small volume of benzene to dissolve the solid in the 5mL volumetric flask, then made-up to the mark by adding a few drops of solvent. Vortexed the solution to mix well and obtained a 1.1M per component solution. This is labeled ONSCExp157-1A
11:20 Performed serial dilution of ONSCExp157-1A as shown in Spreadsheet ONSCExp157 in 2mL volumetric flasks
11:45 Samples 11A and 12A are blanks.
13:30 In to 12 clean half dram vial labeled ONSCExp157-2A through ONSCExp157-10A, containing a small amount of UCExp176C, approximately 500uL of the corresponding (#A series) solution was added. The vials were vortexed and made sure some of the solute still remained at the bottom of the vials. Parafilmed the vials.
13:45 Temperature had reached 40C. Placed the vials in the water/glycol bath at 40C.
2009-12-30
10:25 Changed the setting of the water/glycol bath to 25C.
15:45 Removed the vials from the bath. Centrifuged the vials.
15:55 In to twelve clean/dry NMR tubes, pipetted out DMSO-d6 (~200uL) and labeled the tubes ONSCExp156-1A-1 and ONSCExp157-2A, ONSCExp156-7A, ONSCExp156-7A, ONSCExp157-5A, ONSCExp157-6A, ONSCExp157-7A, ONSCExp157-8A, ONSCExp157-9A, ONSCExp157-10A, ONSCExp157-11A, ONSCExp157-12A.
16:10 Transferred approximately 300uL of the supernatant from each vial in to the corresponding NMR tubes.
20:20 Obtained HNMRs of ONSCExp157-1A-1 through ONSCExp157-12A