Beard reaction

The Bart reaction is a name reaction in organic chemistry , which was first introduced in 1910 by Heinrich Bart and named after him. The reaction is used to produce aromatic arsenic acids by reacting aromatic diazonium compounds with sodium arsenate . The reaction products are mainly used in the pharmaceutical industry and isotope labeling .

The Bart reaction is closely related to the Sandmeyer reaction .

Overview reaction

An aromatic diazonium salt 1 reacts with sodium arsenate 2 in the presence of a catalytic amount of copper (I) chloride to form the disodium salt 3 of an aromatic arsenic acid. Nitrogen and sodium chloride are produced as by-products . Instead of the copper salt, powdered silver or copper can also be used.

Reaction mechanism

It is believed that the Bart reaction proceeds by a radical mechanism. The diazonium compound 1 is first reduced to Cu ²⁺ with oxidation of Cu ⁺ . After splitting off nitrogen, an aryl radical 2 is formed, which combines with sodium arsenate to form radical 3 . Another one-electron shift reduces Cu ²⁺ back to Cu ⁺ . The sodium salt 4 of aromatic arsenic acid is then formed with the elimination of sodium chloride .

modification

The best-known modification of the Bart reaction is the so-called Scheller modification. In this case, an aromatic amine 1 is reacted with arsenic (III) chloride 2 and nitrous acid in the presence of a catalytic amount of copper (I) chloride to form the aromatic arsenic acid 3 .

Individual evidence

↑ Heinrich Bart was a chemist in Bad Dürkheim , where his father was mayor, and discovered (again) the arsenic content of the Maxquelle there in 1906, examined more closely by his Heidelberg teacher Erich Ebler . The method he discovered for the synthesis of aromatic arsenic compounds was important for chemotherapy at the time ( Robert Koch , Paul Ehrlich with Salvarsan ).
↑ ^a ^b ^c ^d ^e Zerong Wang: Bart Reaction . In: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, Inc., Hoboken, NJ, USA 2010, ISBN 978-0-470-63885-9 , pp. 9-12 , doi : 10.1002 / 9780470638859.conrr051 .
↑ Entry on beard reaction. In: Römpp Online . Georg Thieme Verlag, accessed on December 21, 2018.
^ GO Doak: A Modified Bart Reaction . In: Journal of the American Chemical Society . tape 62 , no. 1 , January 1, 1940, p. 167-168 , doi : 10.1021 / ja01858a048 .

[1] Heinrich Bart was a chemist in Bad Dürkheim , where his father was mayor, and discovered (again) the arsenic content of the Maxquelle there in 1906, examined more closely by his Heidelberg teacher Erich Ebler . The method he discovered for the synthesis of aromatic arsenic compounds was important for chemotherapy at the time ( Robert Koch , Paul Ehrlich with Salvarsan ).

[:0-2] Zerong Wang: Bart Reaction . In: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, Inc., Hoboken, NJ, USA 2010, ISBN 978-0-470-63885-9 , pp. 9-12 , doi : 10.1002 / 9780470638859.conrr051 .

[3] Entry on beard reaction. In: Römpp Online . Georg Thieme Verlag, accessed on December 21, 2018.

[4] GO Doak: A Modified Bart Reaction . In: Journal of the American Chemical Society . tape 62 , no. 1 , January 1, 1940, p. 167-168 , doi : 10.1021 / ja01858a048 .