Researcher

Evan Curtin

Objective

To calculate the solubility of 2-phenylbutyric acid in hexane by density method. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider prediction.

Procedure

Make a saturated solution of 2-phenylbutyric acid in hexane. Do this by mixing the solute into the solvent. Heat to around 40-45C. If all solid dissolved, let sit on counter. If there is still solid remaining, decant immediately into a clean container and let the supernatant sit on counter. Let solution stand to equilibriate. If the solid precipitates, decant the supernatant. This is a saturated solution. If there is no solid, evaporate solvent slowly using air (be careful that the temperature doesn't drop too low). Once solid precipitates, decant the solution. This is saturated.

Measure the density of pure solvent by weighing in a volumetric flask (try to get at least 1mL and 2mL). Using these same flasks, measure the density of the saturated solution by weighing. Make sure the flask is clean before weighing each time. Enter density values in the spreadsheet in the results section.

Results

Measured solubility of 2-phenylbutyric acid in hexane.

Discussion

The initial attempt at making a 5M solution was to see if 2-phenylbutyric acid could be miscible with hexane. There was a solid precipitate in this solution, and therefore these two are not miscible. The following samples were all attempts at creating a saturated solution that could be extracted to measure the density. After the final addition of 2-phenylbutyric acid, precipitate was formed when the solution was cooled to 25C and sonicated. This suggests that a saturated solution was made. Enough solution was extracted from the mixture to weigh in a 1mL volumetric flask. In Exp184, it was concluded that cyclohexanecarboxylic acid is miscible in hexane. even though cyclohexanecarboxylic acid and 2-phenylbutyric acid are similar, 2-phenylbutyric acid has a much lower solubility (3.48M for 2-phenylbutyric and 8.06M for cyclohexanecarboxylic acid).

Conclusion

The solubility of 2-phenylbutyric acid in hexane is 3.48M.

References:

http://old.oru.edu/cccda/sl/solubility/allsolvents.php?solute=2-phenylbutyric+acid

Log

2011-02-22

14:53 - Attempted to make a 5M solution by adding 0.8205g 2-phenylbutyric acid to 0.1640g hexane into a twist-cap vial.
15:07 - Bath turned on to 50C, current temperature is 28C
15:21 - Put vial of mixture into the bath, temperature is now 50C. Solid quickly disappeared, forming layers. Sonicated the vial until no solid remained. After a few seconds of the vial being in the room temperature air (20C in the lab), solid precipitate formed. Even more solid came out after sonication. [If solid came out here why did you add more solute? JCB]
15:29 - Added an additional 0.7960g hexane to the vial.
15:31 - Bath temp is 49C. Added vial to bath.
15:32 - Solid started to disappear until only a small amount remained. Sonicated the vial until no solid remained. Added vial to 25C bath.
15:48 - Removed vial from bath. No solid in vial. Sonicated for about 5 seconds. No solid formed after sonication.
15:50 - Added additional 0.4190g phenylbutyric acid to vial.
15:56 - Added vial to 50C bath. Held for about one minute. Most of the solid disappeared. Sonicated until no solid remained. Added to 25C bath.
16:04 - Removed vial from bath. No solid visible in vial. Sonicated for 5 seconds. No solid in the vial after sonication.
16:06 - Added 0.4512g 2-phenylbutyric acid to the vial.
16:08 - Added vial to 50C bath. Held for about one minute. Most of the solid disappeared. Sonicated until no solid remained. Added to 25C bath.
16:14 - Removed vial from bath. No solid visible in vial. Sonicated for 5 seconds. No solid in the vial after sonication.
16:15 - Added 0.5338g 2-phenylbutyric acid to vial, put vial in 50C bath. After about one minute in the bath the solid was almost completely gone. Sonicated until no solid remained. Added to 25C bath.
16:22 - Removed vial from bath, no solid visible. Sonicated the vial for 5 seconds, solution became very cloudy. Let sit on lab bench to settle the precipitate.
16:37 - Weighed 1mL volumetric flasks with the solution and with pure n-hexane.