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Structure cyclopropyl carbanion

Triphenylphosphonium cyclopropylide (279), although not a carbanion , is of interest because its structure has been determined by X-ray crystallography by Schmidbaur and coworkers. The most important feature is the pyramidal configuration of the ylidic C-atom the P-atom is bent out of the plane of the cyclopropyl carbon atoms by 58° There is no analogy to planar methylenecyclopropanes like 280 nor to other ylids all of which are planar As Schmidbaur points out the description of the ylid double bond is becoming a problem. [Pg.782]

As in other areas of organic chemistry, computational investigations have provided important insights into the nature of carbanions, and the results complement the experimental studies. For example, ab initio calculations suggest that the inversion barrier of a methyl anion is ca. 2.2kcal/mol and that the inversion barrier of the ethyl anion is 3.3 kcal/mol. These values contrast with the <0.2 kcal/mol inversion barrier of the resonance-stabilized cyanomethyl anion on the one hand and the ca. 15 kcal/mol barrier for inversion of the cyclopropyl anion via a highly strained transition structure on the other hand. By comparison, the inversion barrier of ammonia is about 5.5 kcal/mol. ... [Pg.315]


See other pages where Structure cyclopropyl carbanion is mentioned: [Pg.73]    [Pg.1072]    [Pg.314]    [Pg.277]    [Pg.110]    [Pg.257]    [Pg.259]    [Pg.261]    [Pg.261]    [Pg.263]    [Pg.780]    [Pg.11]    [Pg.528]    [Pg.1673]    [Pg.11]    [Pg.2102]   
See also in sourсe #XX -- [ Pg.68 ]




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Carbanions, structure

Cyclopropyl carbanions

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