Meyer-Hartmann reaction

The Meyer-Hartmann reaction is a name reaction in organic chemistry , which was named after Christoph Hartmann and Victor Meyer and was first described by them in 1894. During the reaction, iodoxybenzene and iodosobenzene form a diaryliodonium salt with the help of the reagent silver (I) oxide .

Overview reaction

Iodoxybenzene 1 and iodosobenzene 2 react in the presence of silver (I) oxide and water to a diaryliodonium salt, consisting of the Diaryliod- cation 3 and the iodate - Anion 4 . Compounds 1 and 2 are present in the same stoichiometric ratios . In the case of silver (I) oxide, catalytic amounts are sufficient for the reaction to take place. Instead of silver (I) oxide, sodium hydroxide can also be used.

Reaction mechanism

The proposals regarding the reaction mechanism of the Meyer-Hartmann reaction are not uniform. The following describes Zerong Wang's proposal, which explains why only a catalytic amount of silver (I) oxide is required.

First, two equivalents of silver hydroxide are formed by hydration of silver (I) oxide .

{\ displaystyle {\ ce {Ag2O + H2O -> 2 AgOH}}}

Silver hydroxide attacks iodoxybenzene 1 , as iodine has a higher oxidation number in this compound than iodosobenzene 5 . This leads to the formation of compound 2 , phenylsilver 4 being formed with elimination of iodic acid 3 . This is added to iodosobenzene 5 in an addition reaction to form compound 6 , which is then protonated by iodic acid 3 . In addition to the iodate anion 8 , the compound 7 forms , from which silver hydroxide is split off, so that the diaryliodonium salt, consisting of 8 and 9 , is ultimately present.

application

The product of the Meyer-Hartmann reaction, a diaryliodonium salt, is widely used in industry . It can e.g. B. serve as a photoinitiator , since it enters into an efficient cleavage reaction under irradiation . This property is used, for example, in lithography or for polymerization reactions .

Individual evidence

↑ Christoph Hartmann, Victor Meyer: About the iodonium bases . In: Reports of the German Chemical Society . tape 27 , no. 1 , 1894, p. 502-509 , doi : 10.1002 / cber.18940270199 .
↑ ^a ^b Aksel A. Bothner-By, C. Wheaton Vaughan Jr .: The Gross Mechanism of the Victor Meyer and Hartmann Reaction . In: J. Am. Chem. Soc . tape 74 , no. 17 , 1952, pp. 4400-4401 , doi : 10.1021 / ja01137a048 .
^ ^A ^b ^c ^d ^e Zerong Wang: Meyer-Hartmann Reaction . In: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, Inc., Hoboken, NJ, USA 2010, ISBN 978-0-470-63885-9 , pp. 1910-1912 , doi : 10.1002 / 9780470638859.conrr429 .
↑ Entry on diaryliodonium salts. In: Römpp Online . Georg Thieme Verlag, accessed on December 19, 2018.

[1] Christoph Hartmann, Victor Meyer: About the iodonium bases . In: Reports of the German Chemical Society . tape 27 , no. 1 , 1894, p. 502-509 , doi : 10.1002 / cber.18940270199 .

[:0-2] Aksel A. Bothner-By, C. Wheaton Vaughan Jr .: The Gross Mechanism of the Victor Meyer and Hartmann Reaction . In: J. Am. Chem. Soc . tape 74 , no. 17 , 1952, pp. 4400-4401 , doi : 10.1021 / ja01137a048 .

[:1-3] A ^b ^c ^d ^e Zerong Wang: Meyer-Hartmann Reaction . In: Comprehensive Organic Name Reactions and Reagents . John Wiley & Sons, Inc., Hoboken, NJ, USA 2010, ISBN 978-0-470-63885-9 , pp. 1910-1912 , doi : 10.1002 / 9780470638859.conrr429 .

[4] Entry on diaryliodonium salts. In: Römpp Online . Georg Thieme Verlag, accessed on December 19, 2018.