Free-energy relationship

A free energy relationship, also known as a Gibbs energy relationship, relates the Gibbs free energy change of one series of chemical reactions to the of the same or another, related series of reactions.

:<math>\log \mathrm{SP} = c + e\mathrm{E} + s\mathrm{S} + a\mathrm{A} + b\mathrm{B} + l\mathrm{L}</math>

where is some free-energy related property, such as an adsorption or absorption constant, , anesthetic potency, etc. The lowercase letters (, , , , ) are system constants describing the contribution of the aerosol phase to the sorption process. The capital letters (, , , , ) are solute descriptors representing the complementary properties of the compounds. Specifically,

is the gas–liquid partition constant on n-hexadecane at 298 K;
= the excess molar refraction ( for n-alkanes).
= the ability of a solute to stabilize a neighbouring dipole by virtue of its capacity for orientation and induction interactions;
= the solute's effective hydrogen bond acidity; and
= the solute's effective hydrogen-bond basicity.

The complementary system constants are identified as

= the contribution from cavity formation and dispersion interactions;
= the contribution from interactions with solute n-electrons and pi electrons;
= the contribution from dipole-type interactions;
= the contribution from hydrogen-bond basicity (because a basic sorbent will interact with an acidic solute); and
= the contribution from hydrogen-bond acidity to the transfer of the solute from air to the aerosol phase.

Similarly, the correlation of solvent–solvent partition coefficients as , is given by

:<math>\log \mathrm{SP} = c + e\mathrm{E} + s\mathrm{S} + a\mathrm{A} + b\mathrm{B} + v\mathrm{V}</math>

where is McGowan's characteristic molecular volume in cubic centimeters per mole divided by 100.

Biochemistry

In biochemistry, linear free energy relationships are widely used to analyze enzyme reaction mechanisms using series of structurally related substrates

Free-energy relationship

Biochemistry

See also

External links