[Ponyshine]

Hello

The reaction below is a Lewis Acid (CuSO4) catalysed reaction of cyclopentadiene with glyoxylic acid in water:


The work-up then involved extracting the excess cyclopentadiene in cyclohexane and collecting the product in the aqueous water layer. The aq layer was then saturated with NaCl. The product was then extracted into an  organic ethyl acetate solvent layer.

My question is, what exactly is going on during the work-up? Why does the product dissolve in water initially before adding NaCl? And what exactly is happening when the aq layer is saturated with NaCl to make the product soluble in an organic solvent after this saturation? What is the role of the NaCl here to cause the product to go from dissolving in the aq layer to dissolving in the organic layer? Is it affecting the Lewis acid in some way?

Thanks very much!

[pgk]

1). logP < 0 → hydrophilic, logP > 0 → lipophilic.
     (logP refers to the n-octanol/water, binary solvent system).
2). Compounds 1 and 2 have logP ≈ -0.7, which means that they are soluble in both water and polar organic solvents but insoluble in non-polar organic solvents.
3). Aqueous solubility of hydrophilic organic compounds decreases as the salinity increases due to the saturation of the solvent capacity of water.
4). The presence of CuSO4 is synergistic to the NaCl.

[pgk]

NUMERICAL CONTRIBUTION OF MOLECULAR MOIETIES TO THE LogP VALUE:
1 methylene and 5 methines:                     0.50x(1+5) =  3.00
1 hydroxyl:                                                 -1.16x1 = -1.16   
1 ester:                                                     -1.71x1 = -1.71
1 double bond:                                            -0.30x1 = -0.30
2 chain branchings:                                      -0.20x2 = -0.40
2 ring closures:                                            -0.09x2 = -0.18
---------------------------------------------------------------------------
Total:                                                                      -0.75 (= logP in n-octanol/water)     

Partition Coefficients and their Uses, Chemical Reviews, (1971), 71(6), 525–616
http://pubs.acs.org/doi/abs/10.1021/cr60274a001

[Ponyshine]

Thank you!! 

[pgk]

You are welcome. Glad to be helpful.
By the way and according to the above principles, water-miscible solvents can successfully be used for extractions.
E.g. extractions in THF/saturated aqueous NaCl is a convenient separation/purification method for compounds that are not soluble in ordinary extraction solvents.