title: Effect of cyclodextrins on the reactivity of fenitrothion.
abstract: The hydrolysis reaction of fenitrothion was studied in water containing 2% dioxane and in the presence of native cyclodextrins (α-, β- and γ-CD) and two commercially available modified derivatives, namely, permethylated β- and α-cyclodextrin (TRIMEB and TRIMEA, respectively). The kinetics of the reaction in the presence of TRIMEA could not be measured because the complex formed is insoluble and precipitated even at low concentration. On the other hand, the reaction is only weakly affected by the presence of α-CD. The hydrolysis reaction is inhibited by all the other cyclodextrins. From the kinetic data the association equilibrium constants for the formation of the 1:1 inclusion complexes were determined as 417, 511 and 99M(-1) for β-CD, TRIMEB and γ-CD, respectively. Despite the differences in the association constants for β- and γ-CD, the observed inhibition effect is about the same and this is due to the fact that the rate of hydrolysis in the cavity of γ-CD is smaller than that in the cavity of β-CD. The strongest inhibitor is TRIMEB and this result is consistent with the known structure of the complex in the solid state.
authors.affiliation: Instituto de Investigaciones en Físico Química de Córdoba (INFIQC), Departamento de Química Orgánica, Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, Ciudad Universitaria, X5000HUA Córdoba, Argentina.
authors.forename: Natalia M
authors.initials: NM
authors.lastname: Rougier
authors.forename: Dyanne L
authors.initials: DL
authors.lastname: Cruickshank
authors.forename: Raquel V
authors.initials: RV
authors.lastname: Vico
authors.forename: Susan A
authors.initials: SA
authors.lastname: Bourne
authors.forename: Mino R
authors.initials: MR
authors.lastname: Caira
authors.forename: Elba I
authors.initials: EI
authors.lastname: Buján
authors.forename: Rita H
authors.initials: RH
authors.lastname: de Rossi
mesh_terms: D002800:Cholinesterase Inhibitors / Q000737:chemistry*; D003505:Cyclodextrins / Q000737:chemistry*; D004146:Dioxanes / Q000737:chemistry; D005278:Fenitrothion / Q000737:chemistry*; D006868:Hydrolysis; D007306:Insecticides / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D002800:Cholinesterase Inhibitors; D003505:Cyclodextrins; D004146:Dioxanes; D007306:Insecticides; D014867:Water; C025223:1,4-dioxane; D005278:Fenitrothion