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Handbook of Solvents - George Wypych - ChemTech - Ventech!

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13.3 Effects <strong>of</strong> organic solvents on phase-transfer catalysis 825<br />

exception <strong>of</strong> dichloromethane as an organic-phase solvent, most PEGs are themselves partitioned<br />

into the aqueous phase, depending also on the concentration <strong>of</strong> dissolved salts in the<br />

aqueous phase. 35 To improve organic-phase solubility <strong>of</strong> PEG, several dialkyl ethers <strong>of</strong><br />

PEGs as permanganate-PTC catalysts are suggested in Table 13.3.22.<br />

Table 13.3.21 Binding constants for complexation <strong>of</strong> PEGs and some symmetrical<br />

derivatives with sodium cation Na + + PEG = [Na + ⋅PEG] complex<br />

PEG<br />

Log K (binding constant) with various sodium salts<br />

Avg. MW Avg. n HO- CH3O- C2H5O- PhO- cyC5H10N- 200 4.1 1.64 0.5<br />

300 6.4 2.02 1.55 1.25 1.05 1.16<br />

400 8.7 2.26 1.49 1.51<br />

600 13.2 2.59 2.09 1.99 1.87<br />

1000 22.3 2.88 2.55 2.48 2.37 2.46<br />

1500 33.7 3.09 2.86 2.80 2.68<br />

2000 45.0 3.28 3.08 3.05 2.81 3.08<br />

Data obtained from Szabo et al. 112,114,115<br />

Table 13.3.22 Partition <strong>of</strong> PEG-dialkyl ethers<br />

between C 6H 6 and H 2O<br />

PEG Ether<br />

Partitioning, % in<br />

C6H6/% in H2O<br />

C4-PEG1500-C4 14<br />

C6-PEG1500-C6 84<br />

C18-PEG6000-C18 Emulsion<br />

C18-PEG750-Me 108<br />

C18-PEG1900-Me 39<br />

C18-PEG5000-Me 37<br />

C8-PEG5000-Me 12<br />

C4-PEG5000-Me 13<br />

PEG6000

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