chemical reactionis said to have undergone autocatalysis, or be autocatalytic, if the reaction product is itself the catalystfor that reaction.
A "set" of chemical reactions can be said to be "collectively autocatalytic" if a number of those reactions produce, as reaction products, catalysts for enough of the other reactions that the entire set of chemical reactions is self sustaining given an input of energy and food molecules (see
Rate law in autocatalytic reactions
rate lawfor the second order autocatalytic reaction is .
The concentrations of A and B vary in time according to and .
The graph for these equations is a sigmoid curve, which is typical for autocatalytic reactions: these chemical reactions proceed slowly at the start because there is little catalyst present, the rate of reaction increases progressively as the reaction proceeds as the amount of catalyst increases and then it again slows down as the reactant concentration decreases. If the concentration of a reactant or product in an experiment follows a sigmoid curve, the reaction is likely to be autocatalytic.
ethologist Richard Dawkinswrote about autocatalysis as a potential explanation for abiogenesisin his 2004book " The Ancestor's Tale". He cites experiments performed by Julius Rebekand his colleagues at the Scripps Research Institutein Californiain which they combined amino adenosine and pentafluorophenyl ester with the autocatalyst amino adenosine triacid ester (AATE). One system from the experiment contained variants of AATE which catalysed the synthesis of themselves. This experiment demonstrated the possibility that autocatalysts could exhibit competition within a population of entities with heredity, which could be interpreted as a rudimentary form of natural selection.
Examples of autocatalytic reactions
* [http://jchemed.chem.wisc.edu/JCESoft/CCA/CCA3/MAIN/AUTOCAT/PAGE1.HTM Reaction of Permanganate with Oxalic Acid]
*The mechanism of the above reaction [cite journal | title = Revising the Mechanism of the Permanganate/Oxalate Reaction | author = Kovacs KA, Grof P, Burai L, Riedel M | journal = J. Phys. Chem. A | doi = 10.1021/jp047061u | year = 2004 | volume = 108 | pages = 11026]
*Binding of oxygen by hemoglobin
*The spontaneous degradation of
aspirininto salicylic acid and acetic acid, causing very old aspirin in sealed containers to smell mildly of vinegar.
Involvement in life processes
Two researchers, Robert Ulanowicz [Ecology, the Ascendant Prespective”, Robert Ulanowicz, Columbia Univ. Press 1997] and Stuart Kauffman. [Investigations, Stuart Kauffman, Oxford University Press] have suggested that autocatalytic reactions played a central role in the evolution of life, and continue to constitute a basic element in life architecture. See also
Relational order theories
Autocatalytic reactions and order creation
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