每周分子 | Molecule of the Week

Original ACS 美国化学会 ACS美国化学会 2022-07-01

收录于合集 #每周分子 110个

每周分子：苯炔

Molecule of the Week: Benzyne

苯炔是一种极其活泼但尚未被分离出来的有机分子。只能通过苯炔产生的稳定分子来推断它的存在。苯炔的不稳定性在于其三键。

德国弗莱堡大学的Georg Wittig和同事们在1940年报道了苯炔存在的最早证据之一。他们在-78ºC利用氟苯和苯基锂生成了邻-氟苯锂，当将邻-氟苯锂加热到室温时, 氟化锂被脱除，由此产生的高能环烷基与另一个苯基锂分子反应，形成邻-联苯锂。

1953年，麻省理工学院(剑桥，MA)的John D. Roberts和同事们进行的碳-14标记实验表明：苯炔的过渡三键是电中性的——与Wittig提出的双键内盐相反。例如，[1-¹⁴C]氯苯与氨反应得到等量的[1-¹⁴C]苯胺和[2-¹⁴C]苯胺，建立了相邻碳原子的相等关系。

更多关于苯炔的内容，请参见布朗大学Joseph F. Bunnett的《苯炔化学》和昆士兰大学Curt Wentrup的《苯炔的故事》。

苯炔信息速览

CAS登记号	462-80-6
SciFinder命名	1,3-Cyclohexadien-5-yne
分子式	C₆H₄
摩尔质量	76.10 g/mol

【关于每周分子】

自2001年以来，“每周分子”已成为广受欢迎的栏目。多数分子由读者推荐。每个结构都经由科学家审查，并以3-D和平面图像的形式显示，同时附有该分子简介。可以通过美国化学文摘社 (CAS) 提供的SciFinder中的CAS REGISTRY获取“每周分子”的更多信息。CAS REGISTRY中的每条物质信息都展示了物质的CAS登记号、索引名、通用名、商品名、书目信息等其他更多信息。发送邮件至motw@acs.org推荐您感兴趣的分子吧。

Benzyne is a highly reactive organic molecule that has not been isolated. Its existence only can be inferred by the stable molecules it produces. Its instability is the result of its extremely strained triple bond.

One of the first demonstrations of the existence of benzyne was reported in 1940 by Georg Wittig1 and colleagues at the University of Freiburg (Germany). They combined fluorobenzene and phenyllithium at –78 ºC to produce o-fluorophenyllithium, which, when warmed to room temperature, eliminated lithium fluoride. The resulting high-energy cycloalkyne reacted with another phenyllithium molecule to form o-biphenyllithium.

In 1953, carbon-14 labeling experiments conducted by John D. Roberts2 and co-workers at MIT (Cambridge, MA) showed that the transitory triple bond in benzyne is electrically neutral—as opposed to the double-bond zwitterion that Wittig proposed. In one example, the reaction of [1-¹⁴C]chlorobenzene with ammonia gives equal amounts of [1-¹⁴C]aniline and [2-¹⁴C]aniline, establishing the equivalency of the adjacent carbon atoms.

For more on the history and utility of benzyne, see “The Chemistry of Benzyne” by Joseph F. Bunnett at Brown University (Providence, RI) and “The Benzyne Story” by Curt Wentrup at the University of Queensland (Brisbane, Australia).

Benzyne fast facts

CAS Reg. No.	462-80-6
SciFinder nomenclature	1,3-Cyclohexadien-5-yne
Empirical formula	C₆H₄
Molar mass	76.10 g/mol

About Molecule of the Week

MOTW has been a popular feature on ACS website since 2001. Many molecules are suggested by our website visitors. Every structure is reviewed by a scientist and displayed in 3-D and flat images with a brief description. Each week’s molecule also links to a sample record from the CAS REGISTRY, which is searched using SciFinder. Each record displays the registry number, index name and synonyms, bibliographic information, and more. Send us a molecule suggestion at motw@acs.org.

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