Case IIb

Rule 3:
Partitioning of a compound to a monopolar phase will increase with the strength and number of H-bonds that it can form with this phase.

compound	/	solvent	K_{solvent / air}

ethanol	/	decane	38	Bipolar compounds in monopolar phases or monopolar compounds in monopolar phases of opposite polarity => H-bonds occur between the compound i and the bulk phase but not in the cavity energy. Partitioning increases with strength of H-bonds
ethanol	/	cyclohexane	45
ethanol	/	benzene	229
ethanol		isopropylether	470
ethanol	/	heptanedioxane	1920

dioxane	/	CCl₄	4326
dioxane	/	cyclohexane	1106
dioxane	/	ethyl ether	2436
dioxane	/	chloroform	27366
dioxane	/	CH₂Cl₂	18712

For all remaining cases, i.e. partitioning of mono- and bipolar solutes into mono and bipolar phases we cannot derive any simple rule because here H-bonds occur both in the cavity energy and in the interaction energy between solute and phase so that they partially cancel. It is not always a simple task to predict which ones dominate.

For an extreme case, however, we can still set up an additional, valuable rule (although this cannot be derived here):

6) Almost all organic compounds prefer all organic phases over water due to the strong cavity effect in water. (Exceptions are small polar molecules and ionic organic molecules )

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