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list of experiments
Solubility book (3rd Edn)
To ascertain the solubility of
NMR spectroscopy using an acetonitrile as an internal standard.
Saturated solutions of
, 4-chlorobenzaldehyde, 2,6-dichlorobenzaldehyde, 2-chloro-5-nitro-benzaldehyde and 4-nitrobenzaldehyde in methanol were prepared at 25⁰C. The solutions were prepared by mixing together the solute and a starting amount of 200
μl of methanol into a vial. With subsequent additions of solute, were bouts of vortexing; which consisted of 2-3 minutes stints or 6-8 minute concluding stints.
Solutions are then left to equilibriate over a 24h period of time.
The supernatants from each saturated solutions is cautiously collected (100
, either by decanting or by the use of a Pasteur pipette into separate vials. The supernatants are then placed into NMR tubes containing 700
deuterated chloroform (CDCl3) and 10
μl of acetonitrile; which is used as an internal standard from the NMR process. Proton NMR readings of the solutions are obtained with the use of a 500MHz instrument.
[Lousy photos, lads. That's not a big deal in and of itself, but given the poor quality of visual evidence and the obvious splatterings of solute on the sides of some vials, it would be nice to know whether clarification of the supernatants by centrifugation made a difference to the measurements.-BH]
Relaxation Delay (seconds)
The values of molar concentration obtained in this experiment are essentially a reproduction of other experiments previously carried-out. Here, we attempted to ascertain the accuracy and precision as a comparison to those values and to the known values, respectively.
Previous results of veratraldehyde in methanol yielded concentrations of 4.92M and 5.01M, which we were able to reproduce.
A previous solubility study for 2-chloro-5-nitrobenzaldehyde in methanol yielded a concentration of 0.78M, our reproduced value came out to be 0.27M
This study reproduced a previous study's result for 4-chlorobenzaldehyde, which found the solute's concentration in methanol to be 3.55M.
Literature on the solubilty of 4-nitrobenzaldehyde in methanol found it to be 1.228M at 26⁰C (Maccarone, E; Perrini, G. Gazzetta Chimica Italiana vol 112 p 447 (1982). We show a concentration of 0.5M.
[It seems that in our lab we have repeatedly obtained concentration close to 0.5M for nitrobenzaldehyde - JCB]
Previous solubility studies for 4-dimethylaminobenzaldehyde in methanol yielded concentrations of 1.33M and 1.36M, and we were able to reproduce those findings.
A previous solubility study for 2,6-dichlorobenzaldehyde in methanol yielded concentration of 0.12M (Exp205), however our experiment yielded a result of 0.64M result. The difference in our result is significant enough to require another assessment of the solubility for 2,6-dichlorobenzaldehyde in methanol.
Various NMR readings were obtained for each solute. The readings differ in the relaxation times set for the instrument, being 0.3s and 1s. An NMR reading is obtained by detecting the energy released from each individual proton in a sample. By altering the relaxation time, we were trying to make sure that the best readings for the samples were obtained by allowing enough time to transpass to permit all protons to reach a ground state prior to excitement. However, the readings show that the manipulation of the relaxation times had little/no effect on the resulting reading. We interpret this as the little need for time for the protons in the samples to go from an excited state to a ground state.
[What about the relative integrations within protons of the same molecule? JCB]
This experiment served to reproduce some solubility data for these solutes in methanol from previous experiments. In doing so, we can be confident in our obtained values and their accuracy. Furthermore, we obtained data that veratraldehyde and 4-chlorobenzaldehyde are capable of making 2M solutions for the Ugi product.
14:25 A saturated solution of veratraldehyde was prepared in 200
l of methanol in vial "1". The vial was then vortexed for 8-10 minutes. Observed an increase in volume as more solute was able to dissolve into solution, which leads to the conclusion that veratraldehyde has a strong affinity to methanol and is highly dissolvable in the solvent. Solution was vortexed for another 5-8 minute stint.
μl of methanol was added to vial "2". Afterwards, 2-chloro-5-nitrobenzaldehyde solute was added to the vial.
14:40 Solution was vortexed for 1 minute. The solution turned slightly yellowish in color.
μl of methanol was added to the solution.
14:46 Vortexed solution for 2 minutes.
14:49 Added 400
μl of methanol to the solution.
14:50 Vortexed the solution for 2 minutes. Checked the solution, and it was thought that the solute at the bottom may still have been going into solution; therefore vortexing was resumed.
14:53 Vortexed for 3 minutes.
14:57 Solution appeared clear, so more solute was added.
14:58 Vortexed solution for 2.5 minutes.
15:01 Solution appeared clear once more, so more solute was added.
15:02 Vortexed for 2 minutes.
15:04 Some solute was visible at the bottom of the vial, but more was added to leave no doubt that saturation had been reached.
15:06 Solution was vortexed for 2 minutes.
15:09 Too much solute was added, therefore 200
μl of methanol was added.
15:11 Vortexed for 1.5 minutes.
15:13 Another 400
μl of methanol was added.
15:14 Vortexed for 2 minutes.
15:16 Added 600
μl of methanol.
[why so much extra methanol? You only take 100
μl for analysis. -BH]
15:17 Vortexed solution for 2 minutes.
15:20 A saturated solution of 4-chlorobenzaldehyde was prepared in vial "3". The process included a vortex stint of 3 minutes and a final bout of 8 minutes.
15:35 Added 4-nitrobenzaldehyde to vial "4".
15:36 Added 200
μl of methanol. As the 4-nitrobenzaldehyde mixed into solution, some was observed to fall out and settle at the bottom of the vial (it had a sandy-coarse appearance to it)
15:37 Vortexed solution for 2 minutes.
15:40 Added 200
μl of methanol.
15:41 The solution was vortexed for 3 minutes.
16:04 4-dimethylaminobenzaldehyde solute was added to vial "5" and 2,6-dichlorobenzaldehyde solute was added to vial "6".
μl of methanol was added to both vial "5" and vial "6".
16:05 Both vials were vortexed for 2 minutes.
16:08 Added 200
μl of methanol to both vials.
16:11 Vortexed vials for 2 minutes.
16:13 More solute were added to their respective vials.
16:16 Vortexed vials for 4 minutes.
16:21 More solute was added to their respective vials.
16:23 The solutions were vortexed for 7 minutes.
16:30 Added 100
μl of methanol to each vial.
16:32 Vortexed vials for 6 minutes.
16:39 All vials were set a side to reach an equilibrium. Photos of each vial was also taken.
17:20 Photos of all the vials having reached equilibrium were taken.
17:45 Retracted supernatant from each vial, either by decanting or with the use of a Pasteur pipette, and place supernatant into half-dram vials that were labeled corresponding to the vial in which the supernatant came from.
18:00 NMR caps were sterilized with acetone and the acetone was evaporated off using the oven (68⁰C) for less than a minute.
μl of deuterated chloroform (
CDCl3) was added to 6 NMR tubes.
μl of acetonitrile was added to each NMR tube (this was done with great accuracy and care!).
18:17 Added 100
μl of half-dram "1" (veratraldehyde) to NMR tube "1", which was then vortexed for 5 seconds.
18:18 Added 100
μl of half dram "2" (2-chloro-5-nitrobenzaldehyde) to NMR tube "2", which was then vortexed for 5 seconds.
μl of half-dram "3" (4-chlorobenzaldehyde) to NMR tube "3", which was then vortexed for 5 seconds.
μl of half-dram "4" (4-nitrobenzaldehyde) to NMR tube "4", which was then vortexed for 5 seconds.
μl of half-dram "5" (4-dimethylaminobenzaldehyde) to NMR tube "5", which was then vortexed for 5 seconds.
μl of half-dram "6" (2,6-dichlorobenzaldehyde) to NMR tube "6", which was then vortexed for 5 seconds.
Proton NMR readings of the solutions were obtained with the use
of the Varian Unity Inova-500MHz instrument
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