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In chemistry, a Grob fragmentation is an elimination reaction that breaks a neutral aliphatic chain into three fragments: a positive ion spanning atoms 1 and 2 (the "electrofuge"), an unsaturated neutral fragment spanning positions 3 and 4, and a negative ion (the "nucleofuge") comprising the rest of the chain.〔name=Weyerstahl〕 For example, the positive ion may be a carbenium, carbonium or acylium ion; the neutral fragment could be an alkene, alkyne, or imine; and the negative fragment could be a tosyl or hydroxyl ion: The reaction is named for the Swiss chemist Cyril A. Grob. ==History== An early instance of fragmentation is the dehydration of di(tert-butyl)methanol yielding 2-methyl-2-butene and isobutene, a reaction described in 1933 by Frank C. Whitmore. This reaction proceeds by formation of a secondary carbocation followed by a rearrangement reaction to a more stable teriary carbocation and elimination of a t-butyl cation: Albert Eschenmoser in 1952 investigated the base catalysed fragmentation of certain beta hydroxy ketones: The original work by Grob (1955) concerns the formation of 1,5-hexadiene from cis or trans 1,4-dibromocyclohexane by sodium metal:〔 According to reviewers Prantz and Mulzer (2010) the name Grob fragmentation was chosen "in more or less glaring disregard of the earlier contributions". 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「Grob fragmentation」の詳細全文を読む スポンサード リンク
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