boc-alanine
boc-glycine
boc-phenylalanine

Researcher

Khalid Mirza

Objective

To measure the solubility of boc-alanine and boc-phenyl alanine in hexane, acetonitrile, methanol, t-butanol and benzene by the NMR based SAMS method
Solubility of boc-alanine, boc-phenylalanine and boc glycine is also measured in water.

Procedure

A solution of boc-alanine and boc-phenylalanine ws made-up in alanine in hexane, acetonitrile, methanol, t-butanol and benzene by dissolving the acids in ~0.4mL of the solvents in half dram vials. It was ensured that some of the solute remained undissolved in the solution after vortexing the vials for 30s each. The vials were then tightly capped and placed in a temperature control bath set at 45C for 1h. The supernatant from each solution was then quickly poured out in to a new vial before the solutions cooled down. The temperature of the bath was then set to 25C. The supernatants were left in the bath at 25C until they precipitated the solute.
Once they had some solid, the supernatant (mother liquor) from solution was carefully separated and mixed with CDCl3 (or DMSO-d6 for water solutions) . Proton NMR of each sample was obtained to assess the solubility of the acid in the solvent. For water containing samples DMSO-d6 was used to obtained HNMR.

Results

HNMR
boc-L-alanine (methyl appears to have an overlap with the t-butyl at 1.43 and 1.44ppm, chiral proton at 4.16 (m) & 4.15 (m), NH at 5.2 (d), 6.84 (s) H on O, coupling between methyl and the chiral proton is not very prominent, likely due to the rotation along the double bond (ene-amide) (Integration spreadsheet)[You are right - I was confused because you can clearly see the coupling in this spectrum JCB]
boc-L-phenylalanine
boc-L-leucine
boc-L-serine
[Link to SAMS sheet and add to solsum sheet JCB]

Discussion

Conclusion

Log

2010-12-22
14:30 Turned on the heater of the water/glycol bath and set it to 45C
15:00 Made-up a solution of boc-alanine and boc-phenyl alanine in hexane, acetonitrile, methanol, t-butanol and benzene by dissolving a small quantity of the acid in approximately 400uL of the solvent in labeled half dram vials (1-10). The solutions were vortexed and extra solute was added in the vials until no more of the solute dissolved.. Vials 1-5 contained boc-alanine and 6-10 contained boc-phenyl alanine. Solvents: hexane 1,6; acetonitrile 2,7; methanol 3,8; t-butanol 4,9 and benzene 5,10
15:30 Made-up solution of boc-glycine, boc-alanine and boc-phenylalanine in water in three half dram vials. Labeled the vials W1, W2, and W3.
15:35 Placed the vials in the water/glycol bath at 45C.
16:35 Removed vial W1 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled W1A
16:40 Removed vial W2 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled W2A
16:43 Removed vial W3 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled W3A
16:46 Removed vial 1 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 1A
16:50 Removed vial 2 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 2A
16:53 Removed vial 3 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 3A
17:00 Removed vial 4 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 4A
17:03 Removed vial 5 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 5A
17:05 Removed vial 6 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 6A
17:08 Removed vial 7 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 7A
17:10 Removed vial 8 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 8A
17:13 Removed vial 9 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 9A
17:15 Removed vial 10 from the water bath, quickly transferred the supernatant in a previously new half dram vial labeled 10A
17:18 Changed the temperature setting on the water/glycol bath to 25C.
17:35 The supernatants in the 'A' series vials were placed in the water/glycol bath now at 25C.
19:10 Vials W1A, W2A, W3A, 1A and 2A had developed crystals in them therefore removed them from the water/glycol bath at 25C. The remaining vials did not have any solids, they were left at 25C in the bath.
19:20 Small volumes of supernatants from W1A, W2A and W3 were mixed with DMSO-d6 (700uL) in three clean NMR tubes, mixed well.
19:30 Small volumes of the supernatants from sample vials 1A and 2A were mixed with CDCl3 in clean glass vials. The solutions were then transferred in to NMR tubes.
20:00 Obtained HNMR of the solutons W1A, W2A, W3A, 1A and 2A.
2010-12-23
14:10 No precipitation was observed in any of the vials (3A-10A) in the bath at 25C.
14:40 Placed the samples in the sonicator and started to sonicate them.
15:00 Removed from the sonicator and placed them back in to the bath at 25C. No precipitation yet.