0000000001192355
AUTHOR
Vitalba Pace
showing 30 related works from this author
Can the absence of solvation of neutral reagents by ionic liquids be responsible for the high reactivity in base-assisted intramolecular nucleophilic…
2005
[reaction: see text] The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1a) into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (2a) induced by amines have been studied in two room-temperature ionic liquids (IL-1, [BMIM][BF4] and IL-2, [BMIM][PF6]). The data collected show that the reaction occurs faster in ionic liquids than in other conventional solvents previously studied (both polar or apolar, protic or aprotic). Presumably, this could depend on their peculiar ability to minimize the strong substrate-solvent, amine-solvent and amine-amine interactions occurring in conventional solvents.
On the Rearrangement in Dioxane/Water of (Z)-Arylhydrazones of 5-Amino-3-benzoyl-1,2,4-oxadiazole into (2-Aryl-5-phenyl-2H-1,2,3-triazol-4-yl)ureas: …
2006
We have recently evidenced an interesting differential behavior in the reactivity in dioxane/water between the (Z)-2,4-dinitrophenylhydrazone (1a) and the (Z)-phenylhydrazone (1b) of 5-amino-3-benzoyl-1,2,4- oxadiazole. The former rearranges into the relevant triazole 2a only at pS+ > 4.5 while undergoing hydrolysis at high proton concentration (pS+ < 3.5); on the contrary, the latter rearranges into 2b in the whole pS+ range examined (0.1 e pS+ e 14.9). Thus, for a deeper understanding of these differences we have now collected kinetic data on the rearrangement in dioxane/water of a series of 3- or 4-substituted (Z)-phenylhydrazones (1c-l) of 5-amino-3-benzoyl-1,2,4-oxadiazole in a wide ra…
On the application of the extended Fujita-Nishioka equation to polysubstitued system. A kinetic study of the rearrangement of several poly-substitued…
2005
Abstract The rearrangement rates of several di-, tri-, tetra- or penta-substituted Z -arylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole ( 1a – 18a ) into the relevant 2-aryl-4-benzoylamino-5-phenyl-1,2,3-triazoles ( 1b – 18b ) have been determined in 1:1 (v:v) dioxane/water in a wide range of p S + (3.80–12.50) at different temperatures. The kinetic data obtained have been correlated with those previously collected for the rearrangement of ortho -, meta - and para -substituted Z -arylhydrazones ( 19a – 38a ) by means of an extension of the linear free-energy relationship (LFER) proposed by Fujita and Nishioka, thus considering steric ( E s ) and field ( F o ) proximity effects in additi…
Effect of ionic liquid organizing ability and amine structure on the rate and mechanism of base induced elimination of 1,1,1-tribromo-2,2-bis(phenyl-…
2006
Abstract The kinetics of the elimination reaction of 1,1,1-tribromo-2,2-bis(phenyl-substituted)ethanes into the corresponding 1,1-dibromo-2,2-bis(phenyl-substituted)ethenes induced by amines were studied in three room temperature ionic liquids ([BMIM][BF 4 ], [BMIM][PF 6 ], [BdMIM][BF 4 ]). In order to have information about reagent–ionic liquid interactions, the reaction was carried out over the temperature range (293.1–313.1 K). To study the effect of the amine on the rate and occurrence of the elimination reaction, several primary, secondary and tertiary amines with different structure (cyclic and acyclic), basicity and steric requirements were used. The data collected show that the reac…
Room temperature ionic liquids structure and its effect on the mononuclear rearrangement of heterocycles: an approach using thermodynamic parameters.
2006
The kinetics of the rearrangement of the Z-phenylhydrazone of 3-benzoyl-5-phenyl-1,2,4-oxadiazole (1) into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole (2) induced by amines have been studied in five room-temperature ionic liquids (RTILs) at different temperatures. The kinetic data collected show that both cationic and anionic parts of RTILs significantly influence the reactivity of the title reaction. The calculated activation parameters allow us to advance hypotheses about the weak interactions operating in RTIL solutions.
On the characterization of some [bmim][X]/co-solvent binary mixtures: a multidisciplinary approach by using kinetic, spectrophotometric and conductom…
2008
Abstract In order to study the intrinsic characteristics and to evaluate the structural variations determined by the addition of a co-solvent to 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4 ]) we examined the behaviour of some probes in [bmim][BF 4 ]/co-solvent binary mixtures. The rate constants of the piperidino-catalyzed rearrangement of the Z -phenylhydrazone of the 3-benzoyl-5-phenyl-1,2,4-oxadiazole into the relevant 4-benzoylamino-2,5-diphenyl-1,2,3-triazole as well as the spectrometric properties of pyrene and Nile Red were evaluated. With the same purpose also 1 H NMR and conductivity measurements were carried out. By comparison the behaviour of 1-butyl-3-methylimidaz…
Study of aromatic nucleophilic substitution with amines on nitrothiophenes in room-temperature ionic liquids: are the different effects on the behavi…
2006
The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three room-temperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm(2)im][BF4], where bmim = 1-butyl-3-methylimidazolium and bm(2)im = 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration…
On the Dichotomic Behavior of the Z-2,4-Dinitrophenylhydrazone of 5-Amino-3-benzoyl-1,2,4-oxadiazole with Acids in Toluene and in Dioxane/Water: Rea…
2004
The mononuclear rearrangement (MRH) of the Z-2,4-dinitrophenylhydrazone (4a) and of the Z-phenylhydrazone (4b) of 5-amino-3-benzoyl-1,2,4-oxadiazole into the relevant triazoles 5a and 5b in toluene has been quantitatively investigated in the presence of trichloroacetic acid (TCA) and of piperidine at 313.1 K. While the behavior in the presence of piperidine recalls the one previously evidenced for some Z-hydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole, the study of the reactivity in the presence of TCA has most interestingly evidenced a general-acid-catalyzed rearrangement for “both” 4a and 4b. Thus, 4a offers the first example of a solvent-dependent dichotomic behavior in MRH processes o…
Effetto dei sostituenti sulla reattività di alcuni Z-fenilidrazoni del 5-ammino-3-benzoil-1,2,4-ossadiazolo in diossano/acqua
2005
Abilità organizzante di liquidi ionici: effetto sulla velocità di reazioni di trasposizione mononucleare di eterocicli.
2006
Reattività dello Z-fenilidrazone del 5-ammino-3-benzoil-1,2,4-ossadiazolo in toluene in presenza di acidi aloacetici.
2005
Studio cinetico della reazione di eliminazione di 1,1,1-tribromo-2,2-bis(dimetossifenil)etano in liquidi ionici.
2004
Ring-to-ring interconversion: a reactivity study of some substituted Z-phenylhydrazones of the 5-amino-3-benzoyl-1,2,4-oxadiazole.
2005
The “perturbative” effect of cosolvents on the structure of neat bmimBF4 and bmimNTf2 evaluated by means of kinetic measurements.
2006
Catalisi da Cu(II) nelle reazioni di interconversione di anello: uno studio meccanicistico.
Studio cinetico della reazione di sostituzione nucleofila aromatica di alcuni 2-X-3-nitro e 2-X-5-nitrotiofeni in BMIMBF4.
2005
Reattività degli Z-idrazoni, semicarbazoni e fenilsemicarbazoni del 3-benzoil-5-fenil-1,2,4-ossadiazolo: effetto della struttura della catena laterale
2004
Catalisi da sali di Cu(II) nelle reazioni di trasposizione eterociclica mononucleare.
Evidences of the organising ability of ionic liquids on the rate of the elimination reaction.
2005
Studio cinetico della trasposizione di Z-fenilidrazoni polisostituiti del 3-benzoil-5-fenil-1,2,4-ossadiazolo nei corrispondenti 2-aril-5-fenil-1,2,3…
2004
Trasposizioni eterocicliche mononucleari. Reattività di Z-arilidrazoni del 5-ammino-3-benzoil-1,2,4-ossadiazolo in D/W: effetto dei sostituenti
2004
Multidisciplinary learning at the University scientific museums: the Bunsen burner
2017
We report on a laboratory activity carried out together with secondary school (high-school) students, with the aim of increasing their interest toward historical scientific instruments and stimulate their approach to scientific knowledge. To this purpose, we propose a hands-on activity that can be fruitfully performed at the University scientific museums. We organized a one-week summer stage at the Historical Collection of Physics Instruments and at the Museum of Chemistry of the University of Palermo. A group of selected students attended it, under the tutoring of university researchers. They were showed some Bunsen burners belonging to the collections, how they are restored, how they work…
The effect of ionic liquids on the rate of an intramolecular nucleophilic substitution: the study of a monocyclic rearrangement of heterocycles
2004
Effetto della struttura dei liquidi ionici sulla reazione di trasposizione eterociclica mononucleare: un approccio usando i parametri termodinamici
2006
L'assenza di solvatazione può giustificare l'aumento della velocità dei processi di interconversione di anello in liquidi ionici?
2004
Trasposizioni eterocicliche mononucleari. Applicazione dell'equazione di Fujita-Nishioka alla reattività di Z-fenilidrazoni di- e poli-sostituiti del…
2004
Reattività dei fenilidrazoni E e Z del 3-benzoil-5-fenil-1,2,4-ossadiazolo in presenza di sali di Cu(II)
Study of aromatic nucleophilic substitution with amines on nitrothiophenes in RTILs: are the different effects on the behavior of para-like and orto-…
2006
The kinetics of the nucleophilic aromatic substitution of some 2-L-5-nitrothiophenes (para-like isomers) with three different amines (pyrrolidine, piperidine, and morpholine) were studied in three roomtemperature ionic liquids ([bmim][BF4], [bmim][PF6], and [bm2im][BF4], where bmim ) 1-butyl-3- methylimidazolium and bm2im ) 1-butyl-2,3-dimethylimidazolium). To calculate thermodynamic parameters, a useful instrument to gain information concerning reagent-solvent interactions, the reaction was carried out over the temperature range 293-313 K. The reaction occurs faster in ionic liquids than in conventional solvents (methanol, benzene), a dependence of rate constants on amine concentration sim…