Objective

To determine the solubility of the fourteen liquid aldehydes listed below in methanol
2,4-dimethylbenzaldehyde
benzaldehyde
5-bromothiophene-2-carbaldehyde
p-tolualdehyde
p-anisaldehyde
salicylaldehyde
m-anisaldehyde
4-(trifluoromethyl)benzaldehyde
crotonaldehyde (E)
hexanaldehyde
2-phenylpropionaldeyde
cyclohexancarboxaldehyde
diphenylacetaldehyde
p-tolualdehyde


Procedure

A solution of liquid aldehydes in methanol was prepared by adding the aldehyde drop-wise in 600uL methanol in one dram vial. Misciblity of the aldehyde was visually confirmed and pictures were obtained.
[It's not clear to me from this how you tell when the solution is saturated. It might be clearer from the spreadsheet or the pictures but it's important that the procedure itself be clear enough to follow or put in a reference to a general procedure perhaps - CN]
There was an assumption when this and other similar experiments were performed- Analogous to a solution of a solid solute in a liquid solvent; a liquid-liquid solution could be considered saturated, if it forms two immiscible layers (of variable densities) one of the solution which could no longer accommodate the solute and other of the undissolved solute itself. Since separation of layers was not visible even after an addition of significant amount of the aldehyde (solute), it was inferred as completely miscible in the methanol.
I am not sure if defining a completely miscible solution as a "saturated solution" is
well-founded. However for the purpose this experiment was performed it seems reasonable to regard the concentration of the pure solute which is completely miscible in methanol as its maximum attainable concentration in methanol .
[I guess there is an issue here of definitions - at what point do you go from having a solution of solute in solvent to having a solution of solvent in solute if you see what I mean - my personal opinion is that it would better to classify these separately - simply describe them as "fully miscible" - although I am happy to be over-ruled by someone with more experience on this - in any case I think there is a need for a detailed discussion of the rationale here, particularly in the conclusion. Just as a matter of interest, do you get the same result when you add methanol to the solutes? CN] Same result was obtained when methanol was added to excess of aldehyde; this was done in Exp020 when methanol was added drop wise to 2-furaldehyde (~4mL) in a one dram vial.


Results

Fully miscible solutions of aldehydes in methanol.

ExpONS-1-7
ExpONS8-14
Spreadsheet

Discussion

Since all the liquid aldehydes used in this experiment, were found to to be fully miscible in methanol (Separation of layers was not seen during the addition of the aldheydes to methanol). Concentration of their saturated saturated solutions therefore can be calculated using there densities.

Conclusion


The concentrations of liquid aldehydes, and there saturated solutions in methanol are tabulated below.

Aldehyde
Concentration of a
saturated solution
in methanol (M)
2,4-dimethylbenzaldehyde
7.2
benzaldehyde
9.8
5-bromothiophene-2-carbaldehyde
9.2
p-tolualdehyde
8.5
p-anisaldehyde
8.2
salicylaldehyde
10.0
m-anisaldehyde
8.2
4-(trifluoromethyl)benzaldehyde
7.3
crotonaldehyde (pred. trans)
12.2
hexanaldehyde
8.3
2-phenylpropanal
7.5
cyclohexanecarbaldehyde
8.3
2,2-diphenylacetaldehyde
5.7
p-tolualdehyde
8.5


Log

2008-12-21

19:30 Fourteen one dram vials were labelled and 600uL of methanol was added to each.
20:15 Aldehydes used were numbered according to the vials labelled (Vial 1 used aldehyde 1 and so on; in the table below)
1)2,4-dimethylbenzaldehyde
2)benzaldehyde
3)5-bromothiophene-2-carbaldehyde
4)p-tolualdehyde
5)p-anisaldehyde
6)salicylaldehyde
7)m-anisaldehyde
8)4-(trifluoromethyl)benzaldehyde
9)crotonaldehyde (pred.trans)
10)hexanaldehyde
11)2-phenylpropionaldeyde
12)cyclohexancarboxaldehyde
13)diphenylacetaldehyde
14)p-tolualdehyde

20:20 Eight hundred microliteres of each aldehyde was drawn in to a micropipettor and added to the corresponding vial drop wise. After an addition of every few drops the vials was swirled gently to homogenize the solution. All aldehydes went in to methanol easily once mixed.
20:55 Pictures of the vial containing the solutions were taken.

References

Solubility of 2,2-diphenylacetaldehyde in methanol (Google Chart Visualization).