Solvent effects on the rates of some well-known nuclophilic substitution reactions have been analysed in terms of initial—state and transition-state contributions. Where possible, the latter have been further analysed by the method of model solutes, on which solvent effects on a transition state are compared to solvent effects on a solute that might be a suitable model for the transition state....

In the past decade, the remarkable potential of ionic-liquid-based aqueous biphasic systems (IL-based ABSs) to extract and purify a large range of valued-added biocompounds has been demonstrated. However, the translation of lab-scale experiments to an industrial scale has been precluded by a poor understanding of the molecular-level mechanisms ruling the separation or partition of target compou...

Fourteen dyes based on 2,4,5,7-tetranitrofluorene (TNF) as the electron acceptor have been designed and prepared in a one-step synthesis. By modifying donor, optical properties of could be efficiently tuned an absorption ranging between 450 nm 700 determined by UV–visible spectroscopy. To get deeper insight into properties, solvatochromism fourteen has also examined. For all dyes, positive was ...

A practical potentiometric method was applied successfully to experimental electrochemical data in order to determine the autoprotolysis constants (pKap) of water + dimethyl sulfoxide mixtures containing 0-90 % of DMSO by volume at 25° C and 0.1 M ionic strength was maintained in each mixture by NaClO4 solution. The results indicated that water-DMSO mixtures are more basic media than pure water...

A series of chromophores was designed and synthesized using 2-(3-cyano-4,5,5-trimethylfuran-2 (5H) -ylidene) malononitrile (TCF) as the electron acceptor differing from each other by use thirteen different donors. The dyes were characterized for their optical electrochemical properties theoretical calculations also carried out to support experimental results. By changing donor in dyes, absorbin...

The spectral properties of several azulene-oxazolone derivatives containing a phenyloxazolone moiety linked to substituted azulene ring via C=C double bond were studied in different solvents varying polarity. solvatochromism and the ability recognize heavy metal ions investigated. In order estimate contribution non-specific specific solute–solvent interactions, multiple linear regression analys...

The polarities of a wide range of ionic liquids have been determined using the Kamlet-Taft empirical polarity scales α, β and π*, with the dye set Reichardt's Dye, N,N-diethyl-4-nitroaniline and 4-nitroaniline. These have been compared to measurements of these parameters with different dye sets and to different polarity scales. The results emphasise the importance of recognising the role that t...

Excitation and emission fluorescence spectra of 2-naphthol and 2-methoxynaphthalene were measured in a series of pure solvents. The spectral shifts are correlated by the Kamlet-Taft parameters (π*, â, and R). As judged from the π* dependence, both molecules have a negligibly small dipole moment in their ground electronic state, which increases in the excited (S1) state. However, the majority of...

Solute properties are known to be strongly influenced by solvent molecules due to solvation. This is due to mutual interaction as both the properties of the solute and of the solvent strongly depend on each other. The present paper is based on the idea that ionic liquids are cations solvated by anions and anions solvated by cations. To show this (in this system strongly pronounced) interaction ...

The rates of tautomerization of 2-nitrocyclohexanone (2-NCH) have been measured spectrophotometrically at 25.0 +/- 0.1 degrees C in several organic aprotic solvents and their binary mixtures. In cyclohexane the reaction is effectively catalyzed by bases and inhibited by acids while the so-called "spontaneous reaction" appears essentially due to autocatalysis. Apparent second order rate constant...