英语Fragmentation reactions,没搜到大概是中文教材里讲的少吧。这种反应的定义接受度也不高。
Fragmentation reactions, according to the definition of Grob and Schiess , are processes in which the reacting molecule breaks into three fragments according to Equation (149). The electrofugal group Y–B forms a stable cation or neutral molecule, the central group becomes an unsaturated fragment and the nucleofugal group X departs with an electron pair. Alkynes are most commonly formed in fragmentation reactions with substrates of the form Y-C-C double bond C-X, where X is the nucleofuge (e.g., halogen, OSO₂Ar, SeO₂Ar, N₂⁺ ) and Y is a heteroatom able to stabilise the positive charge on carbon. Most commonly, the electrofugal fragment is a carbonyl compound or carbon dioxide.[1]
关键是processes in which the reacting molecule breaks into three fragments,裂成三个部分。
其中比较经典应该是Beckmann fragementation 贝克曼碎裂化反应。[2] 叫fragementation是因为形成了腈、阴离子AO⁻、碳离子三个部分。
记得之前讨论这个反应,有人说“讲这个有必要?看邢大本就好了,因为邢大本上有一切会考的反应,邢大本上没有的东西都不重要。”
这类反应可能真的不重要吧,但是一些学校的有机题库里有很多这类反应,看看也好。
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其实也没有那么不常见,只是很多地方不会提这个说法了。