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A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are methenium , methanium , and ethanium . Some carbocations may have two or more positive charges, on the same carbon atom or on different atoms; such as the ethylene dication .〔 Hansjörg Grützmacher, Christina M. Marchand (1997), "Heteroatom stabilized carbenium ions", Coordination Chemistry Reviews, volume 163, pages 287-344. 〕 Until the early 1970s, all carbocations were called ''carbonium ions''.〔Gold Book definition (''carbonium ion'' ) (HTML )〕 In present-day chemistry, a carbocation is any positively charged carbon atom, classified in two main categories according to the valence of the charged carbon: three in the carbenium ions (protonated carbenes), and five or six in the carbonium ions (protonated alkanes, named by analogy to ammonium). This nomenclature was proposed by G. A. Olah.〔 George A. Olah (1972), "Stable carbocations. CXVIII. General concept and structure of carbocations based on differentiation of trivalent (classical) carbenium ions from three-center bound penta- of tetracoordinated (nonclassical) carbonium ions. Role of carbocations in electrophilic reactions." Journal of the American Chemical Society, volume 94, issue 3, pages 808–820 〕 Carbocations are stabilized by the dispersion or delocalization of the positive charge ==Definitions== Some university-level textbooks discuss carbocations as if they were only carbenium ions,〔''Organic chemistry'' 5th Ed. John McMurry ISBN 0-534-37617-7〕 or discuss carbocations with only a fleeting reference to the older terminology of carbonium ions〔''Organic Chemistry'', Fourth Edition Paula Yurkanis Bruice ISBN 0-13-140748-1〕 or carbenium and carbonium ions. One textbook retains the older name of carbonium ion for carbenium ion to this day, and uses the phrase ''hypervalent carbenium ion'' for CH5+.〔''Organic Chemistry'' by Marye Anne Fox and James K. Whitesell ISBN 0-7637-0413-X〕 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「Carbocation」の詳細全文を読む スポンサード リンク
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