Researcher

Khalid Mirza

Objective

To measure the solubility of some compounds in methanol. For a justification of this project see here.

Procedure

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.

Results

The list of compounds, solvents and measurements is on workbook EXP205-WS1
Picture of a) Saturated solutions b) solutions in 1/2 dram vials c) after evaporation of methanol.
HNMR of 3,4-dimethoxybenzaldehyde
HNMR of 1b-2
Sample number
Solid
Solid dissolved
300uL methanol(mg)
Average
Conc (M)
Std. deviation
1a-2,1b-2
3,4-dimethoxybenzaldehyde
268.32
5.35
0.04
2a-2, 2b-2
o-vanillin
96.95
2.27
0.2
3a-2, 3b-2
4-nitrobenzaldehyde
19.49
0.45
0.03
4a-2, 4b-2
2-methoxy-1-naphthaldehyde
69.43
1.26
0.02
5a-2, 5b-2
4-hydroxybenzaldehyde
121.73
3.28
0.06
6a-2, 6b-2
3,5-dimethoxybenzaldehyde
96.00
1.71
0.31
7a-2, 7b-2
2-chloro-5-nitrobenzaldehyde
48.68
0.78
0.13
8a-2, 8b-2
4-chlorobenzaldehyde
12.69
0.29
0.01
9a-2, 9b-2
2,6-dichlorobenzaldehyde
6.40
0.12
0.00
10a-2, 10b-2
4-dimethylaminobenzaldehyde
61.41
1.33
0.05


Discussion

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 Exp207 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 hemiacetal formation JCB]

Conclusion

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

Log

2008-09-25

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.

2008-09-26

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 1b-2 (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.

Tags


Compound
Inchikey
Inchi
Methanol
OKKJLVBELUTLKV-UHFFFAOYAX
InChI=1/CH4O/c1-2/h2H,1H3
3,4-dimethoxybenzaldehyde
WJUFSDZVCOTFON-UHFFFAOYAT
InChI=1/C9H10O3/c1-11-8-4-3-7(6-10)5-9(8)12-2/h3-6H,1-2H3
o-vanillin
JJVNINGBHGBWJH-UHFFFAOYAB
InChI=1/C8H8O3/c1-11-7-4-2-3-6(5-9)8(7)10/h2-5,10H,1H3
4-nitrobenzaldehyde
BXRFQSNOROATLV-UHFFFAOYAO
InChI=1/C7H5NO3/c9-5-6-1-3-7(4-2-6)8(10)11/h1-5H
2-methoxy-1-naphthaldehyde
YIQGLTKAOHRZOL-UHFFFAOYAN
InChI=1/C12H10O2/c1-14-12-7-6-9-4-2-3-5-10(9)11(12)8-13/h2-8H,1H3
4-hydroxybenzaldehyde
RGHHSNMVTDWUBI-UHFFFAOYAN
InChI=1/C7H6O2/c8-5-6-1-3-7(9)4-2-6/h1-5,9H
3,5-dimethoxybenzaldehyde
VFZRZRDOXPRTSC-UHFFFAOYAG
InChI=1/C9H10O3/c1-11-8-3-7(6-10)4-9(5-8)12-2/h3-6H,1-2H3
2-chloro-5-nitrobenzaldehyde
VFVHWCKUHAEDMY-UHFFFAOYAZ
InChI=1/C7H4ClNO3/c8-7-2-1-6(9(11)12)3-5(7)4-10/h1-4H
4-chlorobenzaldehyde
AVPYQKSLYISFPO-UHFFFAOYAQ
InChI=1/C7H5ClO/c8-7-3-1-6(5-9)2-4-7/h1-5H
2,6-dichlorobenzaldehyde
DMIYKWPEFRFTPY-UHFFFAOYAO
InChI=1/C7H4Cl2O/c8-6-2-1-3-7(9)5(6)4-10/h1-4H
4-dimethylaminobenzaldehyde
BGNGWHSBYQYVRX-UHFFFAOYAG
InChI=1/C9H11NO/c1-10(2)9-5-3-8(7-11)4-6-9/h3-7H,1-2H3

References

Solubility of 4-nitrobenzaldehyde in methanol