Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones.

Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones. Research Abstract Details 

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Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones. Abstract Text:

Shigehisa Uchiyama,Toshiro Kaneko,Hiroshi Tokunaga,Masanori Ando,Yasufumi Otsubo,Shigehisa Uchiyama,Toshiro Kaneko,Hiroshi Tokunaga,Masanori Ando,Yasufumi Otsubo,Shigehisa Uchiyama,Toshiro Kaneko,Hiroshi Tokunaga,Masanori Ando,Yasufumi Otsubo,

The quantitative analysis of ketones using DNPH is usually conducted in the presence of an acid catalyst. However, this method may cause an analytical error because 2,4-dinitrophenylhydrazones have both E- and Z-stereoisomers. Purified ketone-2,4-dinitrophenylhydrazone comprised only the E-isomer. However, under the addition of acid, both E- and Z-isomers were seen. In the case of 2-butanone-, 2-pentanone- and 2-hexanone-2,4-dinitrophenylhydrazone, the equilibrium Z/E isomer ratios were 0.20, 0.21 and 0.22, respectively. In addition, when trace water was added to the hydrazone derivatives in acetonitrile solution, the concentration of ketone derivatives were seen to decrease and the concentration of free DNPH was seen to increase. The decomposition rate of 2-butanone-2,4-dinitrophenylhydrazone was dependent on the concentration of acid-catalysis and reached an equilibrium state - carbonyl, DNPH, hydrazone-derivative and H(2)O - within 10h at 0.1molL(-1) phosphoric acid solution. The equilibrium constants of ketone-2,4-dinitrophenylhydrazones, [carbonyl] [DNPH]/[hydrazone] [H(2)O], were relatively large and ranged from 0.74x10(-4) to 5.9x10(-4). Hydrazone derivatives formed from 2-ketones such as 2-pentanone, 2-hexanone and 4-methyl-2-pentanone showed lower equilibrium constants than corresponding 3-ketones. Consequently, only a minimum concentration of catalytic acid must be added. The best method for the determination of ketone-2,4-dinitrophenylhydrazones by HPLC or GC is to add phosphoric acid to both the standard reference solution and samples, forming a 0.001molL(-1) acid solution, and analyze after 27h.

Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones. Publishing Authors By Initials

S Uchiyama,T Kaneko,H Tokunaga,M Ando,Y Otsubo,S Uchiyama,T Kaneko,H Tokunaga,M Ando,Y Otsubo,S Uchiyama,T Kaneko,H Tokunaga,M Ando,Y Otsubo,

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Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones. Journal Published:

PUBLICATION TYPE: Journal Article

Journal: Analytica chimica acta

VOLUME: 605

Page Numbers: 198-204

Journal Abbreviation: Anal. Chim. Acta

ISSN: 1873-4324

DAY: 25

MONTH: 10

YEAR: 2007

Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones. Information

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LANGUAGE: eng

NlmUniqueID: 370534

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Grant and Affiliation Information for Acid-catalyzed isomerization and decomposition of ketone-2,4-dinitrophenylhydrazones.

AFFILIATION: Faculty of Engineering, Chiba University, 1-33, Yayoi-cho, Inage-ku, Chiba City 263-8522, Japan.

Country: Netherlands

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MEDLINETA: Anal Chim Acta

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