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CHEM 7200 Organic Structures and Mechanisms (Physical Organic Chemistry) In order to imagine where this field is going it is useful to realize where it has been, and a view over the past
 

Summary: CHEM 7200 Organic Structures and Mechanisms (Physical Organic Chemistry)
In order to imagine where this field is going it is useful to realize where it has been, and a view over the past
century is informative. The history of physical organic chemistry fits almost completely in the 20th Century. Its
emergence as a separate discipline can be traced to the beginning of the century, when many aspects of the
subject were beginning to be actively studied. Thus in 1899 Stieglitz (1) published a proposal for the
intermediacy of carbocation intermediates, although without experimental support, and in 1901 Norris (2a,b)
and Kehrmann (2c) independently observed stable solutions of triphenylmethyl cations in solution, and Baeyer
recognized the salt-like nature of these materials (3). In 1900 Gomberg reported convincing studies of the
stable triphenylmethyl radical (4), and although his report aroused considerable skepticism, this species
attracted wide attention, and the results were reproduced in many laboratories. Carbanions also were
becoming clearly understood, and Clarke and Lapworth (5) proposed a mechanism for the critical step in the
benzoin reaction as an aldol type process involving a carbanion and this is essentially the mechanism
accepted today.
In 1914 Schlenk and Marcus (6) reported that triarylmethyl radicals could be reduced to carbanions by alkali
metals, and demonstrated their ionic character by their conductivity, and clearly depicted the negatively
charged intermediates. Carbanions were however not named as such until 1933 (7).
The carbene :CHCO2Et was proposed in 1903 by Buchner and Hediger (8) as a discrete intermediate in the
reaction of benzene with diazoacetic ester N2CHCO2Et leading to cyclopropane intermediates (8). Staudinger
and Kupfer (9) further showed in 1912 that diazomethane formed CH2, which could react with alkenes to form
cyclopropanes, or with carbon monoxide to form ketene CH2=C=O.

  

Source: Andreana, Peter R. - Department of Chemistry, Wayne State University

 

Collections: Chemistry