Researcher

Matthew McBride

Objective

To determine the ability of pentane to remove the 1:1 ethanol/water mixture from trans-cinnamic acid crystals

Procedure

Cinnamic acid (0.2337 g) was added to a 10 mL screw cap test tube. 1:1 ethanol/water (3 mL) by volume was added to the tube. The tube was mixed and the crystals were filtered on a sinter glass funnel. The crystals were washed three times with pentane and allowed to dry on the suction for 1 minute.

Results

Mass of Crystals Recovered: 0.1015 g
Yield: 43%
HNMR Spectrum of product dissolved in acetone

Discussion

The low yield is due to the increased solubility of trans-cinnamic acid upon the introduction of the pentane to the crystals wet with the 1:1 ethanol/water mixture. As the pentane wash is applied, it is believe that small pockets of liquid solution with a high ethanol concentration are forming around the crystals. Trans-cinnamic acid has a solubility of 1.119 M in ethanol, and consequently the crystals are becoming soluble with the washes and passing through the filter.

Conclusion

On compounds that have a good solubility in ethanol, such as trans-cinnamic acid, a pentane wash causes the product to become soluble and pass through the filter.

Log

2013-05-02

12:58 0.2337 g of cinnamic acid was added to a 10 mL screw cap test tube (tube #1).
13:02 A 1:1 ethanol/water mixture was created by pipetting 2 mL of distilled water in a vial and added 2 mL of ethanol. The solution was inverted several times to mix.
13:04 The weight of an empty 5-dram vial (no cap) was 11.7946 g.
13:07 The suction on a sinter glass funnel was turned on one full rotation. 3 mL of the 1:1 ethanol/water solution was added to tube #1. The tube was vortexed to completely wet the crystals with the solvent mixture.
13:15 The wet crystal solution was poured into the sinter glass funnel with suction. The liquid quickly filtered through. The suction was turned off and pentane added to the funnel to cover the crystals (the crystals were moved around using a spatula). The suction was reapplied to filter through the pentane. This process was repeated two additional times for a total of 3 pentane washes. Some of the white cinnamic acid crystals were observed to go through the funnel as the crystals were washed with the pentane. The crystals were allowed to dry on the suction for 1 minute. The crystals were removed to the 5-dram vial.
13:20 The weight of the vial with the crystals were weighed to be 11.8961 g.
14:01 Reagent grade acetone was added to the vial with the product crystals. The crystals dissolved into the acetone. A few drops of the acetone was added to the inner coaxial HNMR tube. The sample was analyzed by 500 MHz HNMR using an outer NMR tube with CDCl3.