Researcher

Matthew McBride

Objective

To determine the amount of water needed to form two layers in an ethanol-pentane binary solvent system for the purpose of washing with pentane after a recrystallization

Procedure

Pentane (2 mL) and ethanol (2 mL) were mixed together in a 5-dram vial. Water was added drop wise until two layers formed in the solution upon the addition of 8 drops of water. The top layer of the solution was analyzed by 500 MHz HNMR spectroscopy.

Results

HNMR spectrum of Vial 2

Discussion

Ethanol and pentane are completely miscible in one another and this was observed in this experiment. However, with the addition of 8 drops of water, the solution separated into two layers of equal volume. This means that with the water present, the ethanol was no longer miscible with the pentane and separated forming a miscible layer with the water.

Conclusion

Eight drops of water were needed in order to form two layers in an ethanol-pentane system.

Log

2013-05-02

11:44 In a 5-dram vial (vial 1), an excess of pentane was added to 2 mL of ethanol. The solution was inverted several times and one single layer was present.
11:46 200 ┬ÁL of distilled water was added to the vial. The vial was inverted several times. The solution separated into approximately equal volume layers.
13:42 1.4230 g of pentane was added to a 5-dram vial (vial 2). 2 mL of ethanol was added to this vial. The two solvents were miscible and a single layer was present.
13:46 Added 5 drops of water. A single layer was present. Added 3 more drops for a total of 8 drops, the solution separated into two layers of approximately equal size.
13:51 A few drops of the top layer of the vial 2 solution was placed in an inner coaxial NMR tube. The inner coaxial tube was placed in an outer NMR tube filled with CDCl3 and the sample was analyzed by 500 MHz HNMR.