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Alicia's Masters Thesis
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Ugi NMR Analysis
To measure the solubility of some compounds in methanol. For a justification of this project see
Methanol is added to 20 one dram vials labeled 1a, 1b, 2a, 2b, etc. same compound is added to a and b vials with the same number, until no more of the solid dissolves in it. This is achieved by vortexing the vial repeatedly. Once the solution gets saturated, the one vials are centrifuged and 300uL of the solution is transferred to a half dram preweighed vial. This vial is set in a speed-vac for overnight evaporation. The dry solid in the vials is weighed the next day to obtained the solubility of the compound in methanol.
The list of compounds, solvents and measurements is on workbook
Picture of a)
solutions in 1/2 dram vials
after evaporation of methanol
HNMR of 3,4-dimethoxybenzaldehyde
HNMR of 1b-2
Sample vials are labeled 1a, 1b, 2a, 2b, etc..such that each solubility test is repeated.
Except for dimethoxybenzaldehydes (3,4 and 3,5), the solubility measurements appear to have worked reasonably well. The observed solubility for O-vanillin compared to vanillin from
is very different, the compounds do have a different substitution pattern, it would be appropriate if the solubility tests for both these samples are redone, in order to verify the results.
Dimethoxybenzaldehydes after evaporation in the speed-vac remained liquids..a HNMR of sample 1b-2 (3,4-dimethoxybenzaldedhye) indicated a small amount of methanol contamination, apart from some impurities (
what is your estimate of these impurities?
) which may be a result of a) hemi-acetalization of the aldehyde b) oxidation to an acid..Based on the integrations of methanol peak (3.33 ppm) with respect to the methoxys (3.77-4.12 PPM)
in the HNMR of 1b-2, methanol contamination is calculated to be no more than 1.85% (
how exactly did you get this number?
). This indicates that the solid is 98.15% of the sample, therefore the conc of the aldehyde is 5.32 in 1b-2 (assuming negligible impurities). Since an HNMR of 6b-2 was not obtained soon after the evaporation (speed-vac) the exact conc of 3,5-dimethoxybenzaldehyde in methanol may not be accurate.
[Marked all the chlorobenzaldehyde derivatives as "Reacts with Solvent" in methanol because of
The solubilities of 9 aldehydes in methanol were recorded.
Not all of these values can be used under these conditions - which ones are not valid? JCB
12:00 Added approximately 1ml of methanol to each one dram vial.
12:30 Saturated each vial with reagents.
13:00 Vortexed each vial for 30 seconds.
14:00 Weighed out small vials, labeled
1a-1,1b-1, 2a-1, 2b-1, 3a-1, 3b-1, 4a-1, 4b-1, 5a-1, 5b-1, 6a-1, 6b-1, 7a-1, 7b-1, 8a-1, 8b-1, 9a-1, 9b-1, 10a-1 and 10b-1
. Sample vials with same number has same solution.
14:15 Pipetted 300ul of solution into smaller vials. Did this twice for each solution.
14:30 Vials 7a and 6b fell over.
14:35 Reweighed new vials.a,
14:40 Pipetted 300ul into each new vial
14:40 Obtained a pic of the saturated solutions
14:58 Obtained a pic of the supernatant in half dram vials
15:15 Put the vials into the Speedvac.
09:15 Stopped the speed-vac, samples all vials except 1a, 1b, 6a and 6b contained solids...these vials still contained liquids...the inside temperature was 30C. Sample vials 1a, 1b contained solutions of 3,4-dimethoxybenzaldehyde and 3,5-dimethoxybenzaldehye. Therefore these sample were left again in the speed-vac to try to further drying them (just in case if there was any remaining methanol)..These vials are not renamed
1a-2,1b-2, 2a-2, 2b-22, 3a-2, 3b-2, 4a-2, 4b-2, 5a-2, 5b-2, 6a-2, 6b-2, 7a-2, 7b-2, 8a-2, 8b-2, 9a-2, 9b-2, 10a-2 and 10b-2
09:30 Weighed out the sample vials which contained dry samples.
10:30 Removed the sample vials
1a-2, 1b-2, 6a-2 and 6b-2
from the speed-vac, these vials still contained liquids in them....obtained weights of the vials. (
how did you get weights in the worksheet if they were not dried completely?
11:20 Obtained HNMR of the solution in sample vial
(3,4-dimethoxybenzaldehyde) and also the pure sample used (crystals from the source)
12:10 Obtained a pic of the sample vials after methanol vials.
Solubility of 4-nitrobenzaldehyde in methanol
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