Inclusion of the insecticide fenitrothion in dimethylated-β-cyclodextrin: unusual guest disorder in the solid state and efficient retardation of the hydrolysis rate of the complexed guest in alkaline solution

Abstract

SummaryAn anhydrous 1:1 crystalline inclusion complex between the organophosphorus insecticide fenitrothion [O,O-dimethyl O-(3-methyl-4-nitrophenyl)phosphorothioate] and the host compound heptakis(2,6-di-O-methyl)-β-cyclodextrin (DIMEB) was prepared and its structure elucidated by single-crystal X-ray diffraction. This revealed two independent host molecules in the asymmetric unit. In one of these, the cavity is occupied by two disordered guest components (distinguishable as rotamers with respect to the P–OAr bond) while in the other, three distinct guest components with site-occupancies 0.44, 0.29 and 0.27 appear, the last having a reversed orientation relative to all the other components. Kinetic studies of the alkaline hydrolysis of fenitrothion in the presence of DIMEB showed a remarkable reduction of 84% in the rate of this reaction relative to that for the free substrate, a value exceeding those previously attained with the native hosts, β- and γ-cyclodextrin, and fully methylated β-cyclodextrin.

Inclusion of trans-resveratrol in methylated cyclodextrins: synthesis and solid-state structures

“…12 . Despite the inclusion of the guest molecule, the DMB molecule retains its ‘round shape’ owing to the formation of the well-known ‘belt’ of intramolecular O2( n )···O3( n −1) hydrogen bonds that link contiguous glucose residues [ 17 – 18 ]. In this complex, the average O···O distance in the belt is 2.83 Å and the O–H···O angles span the range 165–173°.…”

Synthesis of tetrathiafulvalene-containing zirconium(IV) pincers and metallocavitands for hosting fullerenes

“…By modifying the structural parameters of the cavity, a large array of guests with different size, shape and charge can be captured inside the void of the hosts. The advantages that can result from these supramolecular assemblies include the possibility of stabilizing reactive intermediates [2,7], hosting unusual molecules within the cavity [8,9], and controlling reaction rates, regioselectivity and yields of catalytic processes [10][11][12][13][14][15]. Although tailoring of the cavities of cavitands can be done by synthetic pathways in order to improve their performance, the multi-step functionalization can be tedious and low yielding.…”

Stabilization of the pesticide Fenitrothion towardOandNnucleophiles in the presence of cyclodextrins

“…[6] Previously, we have studied the hydrolysis reactions of 1 in the presence of native (α-, β-, and γ-CD) and methylated CDs, all of them showed inhibition of the reaction with saturation kinetics because of the formation of complexes. [4,7,8] We present now the results on the reaction of 1 with piperidine (Pip) in water and the effects of the presence of native CDs on the reactivity and regiochemistry of the reactions of 1 with H 2 O 2 , NH 2 OH, BuNH 2 , and Pip. As in the reaction of 1 with the other N-based nucleophiles studied, in the reaction with Pip, competition between the S N 2(P) and S N 2(C) pathways was also observed.…”

“…[4,8] Table 2 shows the calculated values for the mentioned parameters. The parameter ratios a P /a C and b P /b C are equal to 6.11, whereas the relationship of the observed rate constants in the absence of β-CD [6] k P obs / k C obs is equal to 6.16 at the same conditions ([NH 2 OH] 0 = 0.30, pH = 11.00).…”

“…[2,3] For the last decade, we have been involved in the study of the reactivity of organophosphorus insecticides in the absence and presence of CDs. [4][5][6][7][8] Fenitrothion reacts in water with O-and N-based nucleophiles (Nu) through different pathways depending on the nucleophile (Scheme 1). [6] In this reaction media, the reactions of 1 with NH 2 OH, BuNH 2 , and NH 2 NH 2 showed competition between the S N 2(C) and S N 2(P) pathways, while the S N 2(P) was the only reaction taking place when the Nu was HO À or HOO À ; no evidence of a S N Ar pathway was observed.…”