Researcher

Sozit Kurtu

Objective

To determine the concentration of t-cinnamic acid in ethanol at 20C, 25C and 30C using density measurements and NMR spectroscopy. The additivity of volumes is an assumption and the density of the solid is obtained from ChemSpider prediction.

Procedure

Results

[Make spreadsheet editable by anyone - also missing pure solvent densities - you must use these for the calculation. JCB]
Measurements
[Provide SAMS sheet JCB]
[Report the final measurements here on the wiki as well.JCB]

Discussion

Conclusion

Log

2011-10-31

12:15 - Measured 1.502g t-cinnamic acid.
12:18 - Made solution in 4mL volumetric flask.
12:31 - Submerged solution in 34C hot water bath.
12:35 - Bath temp 33C.
12:40 - Bath temp 31C.
12:43 - Bath temp 30C. Solution is not dissolving. Moving to Rotovap bath.
13:04 - After attempting several other methods, including sonicator bath and water drawn from a different tap, placed sample in a beaker of water on a hotplate.
13:15 - Increased temp to 100C to facilitate heating with greater speed.
13:25 - Increased temp to 150C. Heating of water bath is unusually slow, possibly due to the cooling effect of the hood fan, the relatively small size of the beaker, or a malfunction of equipment.
13:35 - Water bath reached 50C. Stable.
13:40 - Measured 9.477g t-cinnamic acid to ensure a larger sample size.
13:42 - Made solution in 25mL Erlenmeyer flask, as a volumetric of that size was not readily available, and a great degree of precision was not necessary for a saturated solution.
13:44 - Submerged solution in a separate beaker of hot water. Starting temp 34C. First solution of 4mL discarded.
13:49 - Bath of 25mL solution reached 50C, stable.
14:35 - Decanted solutions into three screw-top vials. Withdrew <0.5mL for NMR analysis. Added CDCL3 to NMR tube. Solution precipitated quickly, so the vials were returned to the bath while NMRs were taken.
14:52 - Took NMR spectrum of solution.(NMR-1)
15:03 - Set vials of solution aside in hood for further analysis at a later date.

2011-11-01

12:30 - Put sample A in 20.5C bath.
12:39 - Equilibrated to 20C with ice.
12:42 - Put samples B and C in heating bath. Starting temp: 34C. Again, set hot plate relatively high (150C).
12:48 - Hot bath at 50C and cold bath at 20C.
13:12 - Transferred B and C to 25C and 30C, respectively.
13:14 - Empty flask A0 (5mL) weighs 12.768g.
13:15 - Visually determined that there was Not enough sample A for 5mL. Pipetted sample A into 2mL volumetric flask (A2mL), also transferring ~3-400nm to an NMR tube. Added CDCl3 to NMR tube.
13:16 - Empty flask A1 (2mL) weighs 17.444g.
13:17 - Weighted flask A1 (2mL) weighs 19.154g. Did not notice any immediate precipitation.
13.19 - Empty flask A2 (1mL) weighs 20.378g.
13:20 - Transferred 1mL sample from flask A1 to flask A2. Weighted flask A2 weighs 21.234g.
13:26 - Noted that 30C bath dropped to approx. 29.75C, while 25C bath still stable.
13:36 - 30C bath dropped to 29.25C. Equilibrated to 30C with hot tap water.
14:12 - Empty flask B1 weighs 18.206. Though the same flasks were used for all three samples, cleaning between uses, the stoppers were mixed up.
14:13 - Pipetted sample B into 2mL volumetric flask (B1), also transferring ~3-400nm to an NMR tube. Added CDCl3 to NMR tube. Bath B stable at 25C. Bath C stable at 30C.
14:15 - Weighted flask B1 weighs 19.937g. Did not notice any immediate precipitation.
1417: - Empty flask B2 weighs 20.379g.
14:18 - Transferred 1mL of sample from flask B1 to flask B2. Weighted flask B1mL weighs 21.244g. Some crystals forming.
14:20 - Empty flask C1weighs 18.206.
14:21 - Pipetted sample C into 2mL volumetric flask (C1), also transferring ~3-400uL to an NMR tube. Added CDCl3 to NMR tube. Bath C stable at 30C.
14:23 - Weighted flask C1 weighs 19.994g. [Didn't you use the scale accurate to 0.1 mg? JCB]
14:24 - Empty flask C2 weighs 20.383g. Small amounts of precipitation in C2.
14:23 - Transferred 1mL sample from flask C1 to flask C2. Weighted flask C1mL weighs 21.276g. Increased precipitation.
14:30 - Took NMRs of samples A, B, and C. (NMR2, NMR3, NMR4).