WordNet

(mechanics) the equal and opposite force that is produced when any force is applied to a body; "every action has an equal and opposite reaction"
a response that reveals a persons feelings or attitude; "he was pleased by the audiences reaction to his performance"; "John feared his mothers reaction when she saw the broken lamp"
a bodily process occurring due to the effect of some antecedent stimulus or agent; "a bad reaction to the medicine"; "his responses have slowed with age" (同)response
doing something in opposition to another way of doing it that you dont like; "his style of painting was a reaction against cubism"
an idea evoked by some experience; "his reaction to the news was to start planning what to do"
extreme conservatism in political or social matters; "the forces of reaction carried the election"
(biochemistry) of a process accompanied by the release of energy; "diffusion is an exergonic process"

PrepTutorEJDIC

{名}(…に対する)『反応』《+『to』+『名』》 / 〈U〉(…に対する)(政治的・社会的な)『反動』,逆コース《+『against』+『名』》 / 〈U〉〈C〉化学反応,化学変化 / 〈U〉〈C〉(物理学で)反作用

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2018/12/20 20:20:01」(JST)

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An exergonic reaction (such as cellular respiration) is a reaction that loses energy when the process of the reaction. Activation energy (1) catalyzes the reaction to occur in a spontaneous manner. The progress of the reaction is shown by the line. The change of Gibbs free energy (ΔG) in an exergonic reaction (that takes place under constant pressure and temperature conditions) is a negative value because energy is lost (2).

An exergonic reaction is a chemical reaction where the change in the free energy is negative (there is a net release of free energy),^[1] indicating a spontaneous reaction. For processes that take place under constant pressure and temperature conditions, the Gibbs free energy is used whereas the Helmholtz energy is used for processes that take place under constant volume and temperature conditions.

Symbolically, the release of free energy, G, in an exergonic reaction (at constant pressure and temperature) is denoted as

\Delta G=G_{\rm {products}}-G_{\rm {reactants}}<0.\,

Although exergonic reactions are said to occur spontaneously, this does not imply that the reaction will take place at an observable rate. For instance, the disproportionation of hydrogen peroxide is very slow in the absence of a suitable catalyst. It has been suggested that eager would be a more intuitive term in this context.^[2]

More generally, the terms exergonic and endergonic relate to the free energy change in any process, not just chemical reactions. An example of an exergonic reaction is cellular respiration. This relates to the degrees of freedom as a consequence of entropy, the temperature, and the difference in heat released or absorbed.

By contrast, the terms exothermic and endothermic relate to the overall exchange of heat during a process.

References

^ IUPAC Gold Book definition: exergonic (exoergic) reaction
^ Hamori, Eugene; James E. Muldrey (1984). "Use of the word "eager" instead of "spontaneous" for the description of exergonic reactions". Journal of Chemical Education. 61 (8): 710. Bibcode:1984JChEd..61..710H. doi:10.1021/ed061p710.

UpToDate Contents

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1. 急性輸血反応が疑われる患者に対するアプローチapproach to the patient with a suspected acute transfusion reaction [show details]
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English Journal

The ability of a zinc pyrrolidine complex to catalyze the synthesis of cyclic carbonates from carbon dioxide and epoxides: a mechanistic theoretical investigation.

Marino T1, Ponte F, Mazzone G, Sicilia E, Toscano M, Russo N.
Dalton transactions (Cambridge, England : 2003).Dalton Trans.2017 Jul 18;46(28):9030-9035. doi: 10.1039/c7dt01642e.
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Does H4SO5 exist?

Murillo F1, Vargas-Caamal A, Pan S, Cabellos JL, Mora-Fonz MJ, Muñoz-Castro A, Restrepo A, Merino G.
Physical chemistry chemical physics : PCCP.Phys Chem Chem Phys.2017 Jul 14;19(26):17088-17093. doi: 10.1039/c7cp01328k. Epub 2017 Jun 21.
PMID 28636012