Exergonic reactions (from the Greek. Έξω - outside, out and Greek. Έργον - work, action), also spontaneous reactions - according to the second law of thermodynamics, these are chemical reactions that occur without an influx of energy from outside. The free energy of such reactions is always negative, i.e. ΔG ° <0 [1] . Most of the chemical reactions that take place in the environment are exergonic; as a result, they are thermodynamically favorable, in contrast to endergonic ones . Examples of exergonic reactions are the processes of electrolytic dissociation , oxidation and combustion , sorption processes, photochemical processes ( photodissociation , photosynthesis ), in living organisms these are processes of catabolism - glycolysis , lipolysis , proteolysis , fatty acid oxidation, and many others.
Thermodynamic Description
Exergonic reactions occur spontaneously , they do not require external energy. Such reactions proceed with a decrease in the Gibbs energy and if the absolute value of ΔG ° is large, then such reactions proceed almost to the end (they are irreversible ) [2] . The equilibrium constant of exergonic reactions is related to the value of the Gibbs energy by the following equation:
where T is the absolute temperature , R is the universal gas constant equal to 8.3144 J / (mol * K). Given that the value of ΔG ° <0, the value of the equilibrium constant will be greater than 1.
Consequently, the direction of the course of such reactions is from left to right (direct reaction), and the equilibrium shifts toward the formation of reaction products.
See also
- Endergonic reactions
- Gibbs Energy
- Chemical thermodynamics
Notes
- ↑ IUPAC Gold Book definition: exergonic (exoergic) reaction
- ↑ E.S. Severin. Biochemistry. - M: GEOTAR-MED, 2004 .-- 779 p. - ISBN 5-9231-0254-4 .