Exp023

=Objective= To determine the solubility of 2-naphthaldehyde, 4-hydroxybenzaldehyde, 4-nitrobenzaldehyde, //o//-vanillin and piperonal in methanol by UV-Vis spectroscopy using molar absorptivities ( ε) obtained from NIST database. =Procedure= Saturated solutions of 2-naphthaldehyde, 4-hydroxybenzaldehyde, 4-nitrobenzaldehyde, //o//-vanillin and piperonal in methanol were prepared in one dram vials and left to equilibrate for 24 hours. The supernatant from each solution was then decanted in to a different vail and subjected to dilutions until UV absorbance for them fell between 0.5-2.0 absorbance units. Using ε values obtained from NIST database for each aldehyde, concentration of their saturated solution was calculated.

=Results= [|Saturated solutions-day1] [|Saturated solutions -day2] [|After decanting]

2-naphthaldehyde [|ONSExp023A-3] [|ONSExp023A-3'] [|ONSExp023A-3a] [|ONSExp023A-3b] [|ONSExp023A-3c] [|ONSExp023A-3d] [|ONSExp023A-3e] [|ONSExp023A-3a-e]

=Discussion=
 * [Where is the Spreadsheet with the calculations? JCB]**

NIST UV spectral data **[NIST doesn't report the solvent so you'll have to look up the references to find out - also look on Beilstein for methanol and these solutes JCB]**
 * Aldehyde || Wavelength nm || Log ε || ε ||
 *  [|2-naphthaldehyde] || 246.9 || 4.361005 || 22961.75 ||
 * || 282.7 || 3.9638 || 9200.258 ||
 * || 339.9 || 3.2636 || 1834.848 ||
 * [|4-hydroxybenzaldehyde] || 93.5 || 4.259 || 18155.16 ||
 * [|4-nitrobenzaldehyde] || 260 || 4.1982 || 15783.38 ||
 * || 300.6 || 3.3212 || 2095.077 ||
 * || 338.7 || 2.413 || 258.8213 ||
 * [|o-vanillin] || 220 || 4.226 || 16826.74 ||
 * || 265.1 || 3.99696 || 9930.246 ||
 * || 348 || 3.3589 || 2285.073 ||
 *  [|piperonal] || 233.4 || 4.04501 || 11092 ||
 * || 274.2 || 3.8012 || 6327.032 ||
 * || 313 || 3.92295 || 8374.329 ||

= =

=Conclusion= Experiment aborted. =Log=

2009-01-03
11:00 Made-up saturated solution of 2-naphthaldehyde, 4-hydroxybenzaldehyde, 4-nitrobenzaldehyde, //o//-vanillin and piperonal in methanol. This was done by vortexing each of them for 10 min after it appeared like the solution had become saturated. Solutions of piperonal and o-vanillin continued to become clear after vortexing, however once they were left undisturbed for 15-20 they started recrystallizing. Therefore they had to be revortexed, they formed clear solution again...after repeating this process 3 times..the clear solutions were left in the hood...soon after they started to recrystallize, with some supernatant in them..it is assumed that this supernatant solution is the saturated solution.


 * [Do you have any way to record ambient temperature (and its fluctuations) in the vicinity of your hood? Or any way to ensure that the solutions remain at a constant temperature? It seems to me that solubility data should always come with temperature anyway... -BH]**

11:20 The solutions were left in the hood to equlibrate. 18:40 Obtained a picture of the solutions.

2009-01-04
12:30 Centrifuged the vials for 1min, obtained a picture. [saturated solutions-day2] 12:40 Decanted the supernatant from the vials in to 5 new one dram vials labeled 1-5. Obtained a picture. [After decanting] 15:00 Performed dilutions of the saturated solution of 2-naphthaldehyde in methanol as described below
 * Solution ID || Description ||
 * 23A || Saturated solution ||
 * 23A-1 || 100uL 23A in a 10mL Volumetric flask ||
 * 23A-2 || 100uL 23A-1 in a 10mL Volumetric flask ||
 * 23A-3 || 100uL 23A-2 in a 10mL Volumetric flask ||
 * 23A-3a || 125uL 23A-2 in a 10mL Volumetric flask ||
 * 23A-3b || 150uL 23A-2 in a 10mL Volumetric flask ||
 * 23A-3c || 175uL 23A-2 in a 10mL Volumetric flask ||
 * 23A-3d || 200uL 23A-2 in a 10mL Volumetric flask ||
 * 23A-3e || 225uL 23A-2 in a 10mL Volumetric flask ||