54608-84-3Relevant academic research and scientific papers
CYCLIZATION AND ACID-CATALYZED HYDROLYSIS OF O-BENZOYLBENZAMIDOXIMES
Grambal, Frantisek,Lasovsky, Jan
, p. 2786 - 2797 (2007/10/02)
Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media.It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1percent solutions of mineral acids.Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed.From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid.The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.
CYCLIZATION OF O-BENZOYLBENZAMIDOXIME DERIVATIVES IN WATER-ALCOHOL MEDIA
Grambal, Frantisek,Lasovsky, Jan
, p. 2722 - 2729 (2007/10/02)
O-Benzoylated benzamidoximes give 1,2,4-oxadiazoles (yields above 90percent) in water-alcoholic media of pH = 2.45 to 6.20.The cyclization rate has been studied with 28 derivatives containing different substitutents.The reaction is accelerated by electron-donor substituents at 4-position of benzamidoxime and by electron-acceptor substituents at 4'-position of benzoyl.The dependence of the rate constants vs ? values of the substituents fulfils the two-parameter Hammett equation at a 99percent probability level.The activation parameters have been determined, and effects of polarity of medium, kinetic isotopic effect, and the reaction mechanism are discussed.
