To determine the solubility of N-Cbz-proline in methanol


A saturated solution of N-Cbz-L-proline was prepared in methanol by dissolving the solute in methanol (200uL) in a half dram vial with a screw-cap. The solution was vortexed and placed in a water-glycol bath at 40C for 3h, the temperature of the bath was then dropped down to 25C. The vial with the saturated solution remained in the bath for the next 4h. The supernatant (100uL) was then placed in clean and dry NMR tube containing CDCl3 (600uL). A HNMR was obtained and the concentration of the saturated solution was measured by SAMS method.


Cbz-L-proline HNMR in CDCl3
Cbz-L-proline saturated solution in methanol



Solubility of Cbz-L-proline in methanol has been determined to be 4.26 +/- 0.03M


11:30 To a clean half dram vial, added 200uL methanol.
11:35 Added 2 scoops of Cbz-L-proline to it, the solid dissolved almost immediately in to the solvent..vortexed for a few seconds.
11:40 Added about 3 scoop more of the solute to the vial, vortexed it further..it almost dissolved the solid completely.
11:50 Added another 3 scoops of the solid and vortexed the vial for few seconds...this time the solid remained at the bottom of the vial.
12:00 Placed the vial in a bath maintained at 40C
12:30 All the solid had disappeared, therefore added another two scoops of the solute, vortexed the vial to mix well and then placed it back in the bath at 40C
15:00 Changed the temperaturte of the bath to 25C
19:00 Removed the vial from the bath.
19:20 Placed 600uL CDCl3 in to a clean and dry NMR tube
19:30 Pipetted out 100uL of the supernatant from the vial in to the NMR tube and mixed the solution well. This solution is labeled ONSCExp134-1A
19:00 Obtained HNMR of the ONSCExp134-1A in CDCl3 on a 500MHz Varian unity inova with 50s delay (d1) and 8 transients.