Search

The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole induced by amines is studied in two room-temperature ionic liquids, 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM] and hexafluorophosphate [BMIM] [PF(sub 6)]. The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents.

Research has been conducted on the beta-cyclodextrin. The role of this compound in the (Z)-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole's mononuclear heterocyclic rearrangement has been investigated and the results are reported.

The importance of electronic effect of the substituents present on the aromatic ring is evaluated by considering both electron-withdrawing and donor substituents and the importance of the steric effects of the substituents both para- and ortho-substituted benzoic acids is analyzed. The ortho-steric effect has operated differently in water and in the aromatic ionic liquid, determining in this solvent medium a particular behavior for ortho-substituted benzoic acids.

The kinetics of nucleophilic aromatic substitution of three nitrothiophene derivatives in different [1-butyl-3-methylimidazolium][[N.sub.3]]/ionic liquid binary mixtures are analyzed. The studies have shown that a simple linear dependence of the pseudo-first kinetic constant from nucleophile concentration is detected as a consequence of the ability of all solvent media to favor the leaving group departure.

The stability constants relevant to the formation of amine/p-nitrophenol ion pairs are determined in different ionic liquids at 298 K to evaluate the basic strength of aliphatic amines in ionic liquid solution. The comparison between data collected with the one obtained by ordinary molecular solvents provide evidence that ionic liquids as solvent media are able to support the amine basicity and the whole parameters affecting the tridimensional structure should be considered to rationalize the experimental trends obtained for different ionic liquids.

The protonation equilibrium of sodium p-nitrophenolate in [[bm.sub.2]im][N[Tf.sub.2]] and in [bmpyrr][N[Tf.sub.2]] is studied by using spectrophotometric titration in order to obtain an acidity scale in room-temperature ionic liquid solutions. The studies have shown that the carboxylic acids in ionic liquid solutions are less dissociated than in water solution and the equilibrium are affected by both the nature of the ionic liquids and the carboxylic acids.

The nucleophilic aromatic substitution of some activated aryl or heteroaryl halides is performed in ionic liquid solution, by using the 1-butyl-3-methylimidazolium azide as a nucleophile. The studies have shown that in some cases it is possible to obtain aromatic or heteroaromatic azide derivatives in good yields by means of [S.sub.N]Ar reaction by using [bmim][[N.sub.3]] as the nucleophile.

A [bmim][B[F.sub.4]] solution at 298 K was employed to study the amino induced elimination of benzisoxazole into the relevant [ortho]-cyanophenolate ion (Kemp elimination). The data obtained revealed that the target reaction is sensitive to amine structure rather than to amine basicity and cyclic secondary amines are more effective than acyclic ones.

A study investigated the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole induced by amines in five room-temperature ionic liquids (RTILs) at different temperatures. The kinetic data collected reveal that both cationic and anionic parts of RTILs significantly affect the reactivity of the title reaction.

The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes with three different amines was studied in room-temperature ionic liquids (RTIL). The dimensions and charge distributions of anions as well as the hydrogen-bond ability of cations in the used RTIL were found to have an influence on the reaction rate of the nitrothiophenes.

Abstract: By means of simple polarimetry, we studied the binding abilities of native α-, β-, and γ-cyclodextrins toward a group of suitably chosen model guests. We were able to get reliable estimations of the binding constants K, spread over a wide range (from 3.7 to 12,300M−1), allowing us to carry on interesting comparisons. A comprehensive discussion of polarimetric data, and in particular a detailed analysis of the variations ΔΘ of molar optical activities consequent to inclusion, offered us the opportunity to get useful insights into the structure and dynamic behavior of host–guest complexes. [Copyright &y& Elsevier]