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Redox is a contraction of the name for chemical reduction-oxidation reaction. A reduction reaction always occurs with an oxidation reaction. Redox reactions include all chemical reactions in which atoms have their oxidation state changed; in general, redox reactions involve the transfer of electrons between chemical species. The chemical species from which the electron is stripped is said to have been oxidized, while the chemical species to which the electron is added is said to have been reduced. Oxygen is not necessarily included in such reactions as other chemical species can serve the same function. The term "redox" comes from two concepts involved with electron transfer: reduction and oxidation.〔(【引用サイトリンク】url= http://www.wiley.com/college/boyer/0470003790/reviews/redox/redox.htm )〕 It can be explained in simple terms: * Oxidation is the ''loss'' of electrons or an ''increase'' in oxidation state by a molecule, atom, or ion. * Reduction is the ''gain'' of electrons or a ''decrease'' in oxidation state by a molecule, atom, or ion. Although oxidation reactions are commonly associated with the formation of oxides from oxygen molecules, these are only specific examples of a more general concept of reactions involving electron transfer. Redox reactions, or oxidation-reduction reactions, have a number of similarities to acid–base reactions. Like acid–base reactions, redox reactions are a matched set, that is, there cannot be an oxidation reaction without a reduction reaction happening simultaneously. The oxidation alone and the reduction alone are each called a ''half-reaction'', because two half-reactions always occur together to form a whole reaction. When writing half-reactions, the gained or lost electrons are typically included explicitly in order that the half-reaction be balanced with respect to electric charge. Though sufficient for many purposes, these descriptions are not precisely correct. Oxidation and reduction properly refer to ''a change in oxidation state'' — the actual transfer of electrons may never occur. The oxidation state of an atom is the fictitious charge that an atom would have if all bonds between atoms of different elements were 100% ionic. Thus, oxidation is better defined as an ''increase in oxidation state'', and reduction as a ''decrease in oxidation state''. In practice, the transfer of electrons will always cause a change in oxidation state, but there are many reactions that are classed as "redox" even though no electron transfer occurs (such as those involving covalent bonds). There are simple redox processes, such as the oxidation of carbon to yield carbon dioxide () or the reduction of carbon by hydrogen to yield methane (CH4), and more complex processes such as the oxidation of glucose (C6H12O6) in the human body through a series of complex electron transfer processes. ==Etymology== "Redox" is a combination of "reduction" and "oxidation". The word ''oxidation'' originally implied reaction with oxygen to form an oxide, since dioxygen (O2 (g)) was historically the first recognized oxidizing agent. Later, the term was expanded to encompass oxygen-like substances that accomplished parallel chemical reactions. Ultimately, the meaning was generalized to include all processes involving loss of electrons. The word ''reduction'' originally referred to the loss in weight upon heating a metallic ore such as a metal oxide to extract the metal. In other words, ore was "reduced" to metal. Antoine Lavoisier (1743–1794) showed that this loss of weight was due to the loss of oxygen as a gas. Later, scientists realized that the metal atom gains electrons in this process. The meaning of ''reduction'' then became generalized to include all processes involving gain of electrons. Even though "reduction" seems counter-intuitive when speaking of the gain of electrons, it might help to think of reduction as the loss of oxygen, which was its historical meaning. The electrochemist John Bockris has used the words ''electronation'' and ''deelectronation'' to describe reduction and oxidation processes respectively when they occur at electrodes. These words are analogous to protonation and deprotonation, but they have not been widely adopted by chemists. The term "hydrogenation" could be used instead of reduction, since hydrogen is the reducing agent in a large number of reactions, especially in organic chemistry and biochemistry. But, unlike oxidation, which has been generalized beyond its root element, hydrogenation has maintained its specific connection to reactions that ''add'' hydrogen to another substance (e.g., the hydrogenation of unsaturated fats in saturated fats, R-CH=CH-R + H2 → R-CH2-CH2-R). The word "redox" was first used in 1928. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「redox」の詳細全文を読む スポンサード リンク
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