Objective

To establish a method of measuring the solubility of some compounds in organic solvents. For a justification of this project see here.

Procedure

Solid is added to 1.5 mL Eppendorf tubes containing 500 uL of solvent until saturated after 30 s of vortexing. The tubes are then centrifuged for 60 s then 200 uL of clear solution is transferred to pre-weighed 1.5 mL Eppendorf tubes. The tubes with the clear solution are then evaporated down in a SpeedVac for 2 h and re-weighed to obtain the amount of dissolved solid.

Results

The list of compounds, solvents and measurements is on workbook 207-WB1
The pics are tagged as EXP207 on Flickr.

Discussion

This technique was adequate to measure solubilities of the following compounds:
boc-glycine in methanol (4.40 M) and THF (3.45 M)
glycine methyl ester in methanol (1.32 M)
vanillin in methanol (4.19 M) ethanol (2.50 M) THF (3.89 M)

The solubility of boc-glycine in ethanol was measured at 3.57 M but because it appeared as a gel it should be put back on the speedvac to see if a powder can be obtained.

All other compounds measured to less than 5 mg and should be redone using much more solvent to get an accurate measurement.

Conclusion

This method is suitable for compounds of high solubility (on the order of over 0.5M). To obtain an accurate measurement of lower solubilities much more solvent will need to be evaporated.

Log

2008-09-03

11:00 set up 6x3 array of 1.5 mL Eppendorf tubes (A series)
11:05 numbered A tubes 1-18
11:06 added one scoop of solids to about 0.5 mL mark on A tubes
11:12 completed addition of solids
11:15 took pic of tubes A 1-6 207-P1
11:16 took pic of tubes A 7-12 207-P2
11:17 took pic of tubes A 13-18 207-P3
11:20 started adding solvents (500 uL)
11:26 completed addition and put on screw caps
11:29 started vortexing A tubes 2 at a time for 30 seconds each
11:31 dropped tubes 7 and 8 during vortexing but nothing leaked
11:34 finished vortexing
11:36 took pic of tubes A 1-6 207-P4
11:37 took pic of tubes A 7-12 207-P5 then took pic of tubes A 13-18 207-P6
11:38 added more boc-gly to A tubes 1,7,13
11:40 vortexed A tubes 1,7,13 for 30 sec
11:42 added more boc-gly to A tubes 1,7,13 then vortexed 30 sec
11:45 added more boc-gly to A tubes 1,7,13 then vortexed 30 sec
11:47 added more boc-gly to A tube 1 then vortexed 30 sec
11:50 added more vanillin to A tubes 3,9,15 then vortexed 30 sec
11:52 added more vanillin to A tubes 3,15 then vortexed 30 sec
11:56 added more vanillin to A tubes 3,15 then vortexed 30 sec
11:58 took pic A tubes 1-6 207-P7
11:59 took pic of tubes A 7-12 207-P8 then took pic of tubes A 13-18 207-P9
12:01 took pic of tubes A 1,7,13 lying down 207-P10
12:02 centrifuged A tubes at 13,200 RPM (15.79G) for 60 sec
12:05 transferred A tubes to room 5017 where temp is monitored
12:30 weighed out 18 empty 1.5 mL Eppendorf tubes (B series)
12:39 finished weighing
12:40 measured 200 uL of water and obtained weight of 0.1992 g to ensure calibration of pipette and balance
12:42 weighed 200 uL of methanol and obtained weights of 0.1689g, 0.1642g and 0.1642g
12:50 added 200 uL of clear solutions from A tubes to B tubes
12:59 took pic of all B tubes 207-P11 and 207-P12
13:13 put B tubes on SpeedVac
15:07 stopped SpeedVac
15:15 weighed B tubes
15:30 took pic of tubes B 1-6 207-P13 and 207-P14 then took pic of tubes B 7-12 207-P15 then took pic of tubes B 13-18 207-P16
15:40 took pic of researchers 207-P17

References

Solubility of vanillin in methanol (solubility data viewer)