Objective

To verify the concentrations of 0.25M 4-pyrenebutanoic acid solution and 1.25M crotonic acid solution in DMSO by HNMR.

Procedure

A 0.25M solution of 4-pyrenebutanoic acid and 1.25M solution of crotonic acid made-up in DMSO was subjected to HNMR analysis inorder to validate the method. This was achieved by varying the delay time (d1) between the 900 pulses on the sample in the magnetic field.

Results

4PBA-d1=0.3
4PBA-d1=15
4PBA-d1=30
CA-d1=0.3
CA-d1=15
CA-d1=30

Spreadsheet

[I take these data to mean that although the "SAMS" method is independent of volume measurements there may still be considerable variation introduced by NMR settings. Two questions: 1. how well do you trust your standard solutions -- e.g. should you have made and tested more than one? 2. will the NMR settings that appear optimal in this experiment be useful in all further expts, or will this need to be optimised for each solvent and/or solute? If possible please try to answer (2) in terms that an NMR-doofus can understand because it's a long time since I worked with these concepts! --BH]

Discussion

[Redo with baseline corrected SAMS spreadsheet and report your findings JCB]

Conclusion


Log

2009-03-05

20:00 Made-up a solution of 4-pyrenebutanoic acid by dissolving 72.5mg in DMSO in a 1mL volumetric flask. The solution was made up to the mark. The concentration of this solution is 0.2514M - Khalid
20:30 Made-up a solution of crotonic acid by dissolving 108.3mg in DMSO in a 1mL volumetric flask. The solution was made up to the mark. The concentration of this solution is 1.258M - Cedric
21:00 In to two clean and dry NMR tubes CDCl3 (700uL) was pipetted out. To the first tube 100uL of 0.2514M 4-pyrenebutanoic acid solution was added. To the second NMR tube also 100uL of freshly prepared 1.258M crotonic acid solution was added.
22:20 HNMR spectra of both the samples were obtained setting the following parameters a) d1=0.3s, b) d1=15s, c) d1=30s. [A basic 1D pulse sequence uses d1 delay between pw90]