Structural transition in alcohol-water binary mixtures: A spectroscopic study

Abstract

The strengthening of the hydrogen bonding (H-bond) network as well as transition from the tetrahedral-like water network to the zigzag chain structure of alcohol upon increasing the alcohol concentration in ethanol-water and tertiary butanol (TBA) -water mixtures have been studied by using both steady state and time resolved spectroscopy. Absorption and emission characteristics of coumarin 153 (C153), a widely used non-reactive solvation probe, have been monitored to investigate the structural transition in these binary mixtures. The effects of the hydrogen bond (H-bond) network with alcohol concentration are revealed by a minimum in the peak frequency of the absorption spectrum of C153 which occur at alcohol mole fraction ~0⋅10 for water-ethanol and at ~0⋅04 for water-TBA mixtures. These are the mole fractions around which several thermodynamic properties of these mixtures show anomalous change due to the enhancement of H-bonding network. While the strengthening of H-bond network is revealed by the absorption spectra, the emission characteristics show the typical non-ideal alcohol mole fraction dependence at all concentrations. The time resolved anisotropy decay of C153 has been found to be bi-exponential at all alcohol mole fractions. The sharp change in slopes of average rotational correlation time with alcohol mole fraction indicates the structural transition in the environment around the rotating solute. The changes in slopes occur at mole fraction ~0⋅10 for TBA-water and at ~0⋅2 for ethanol-water mixtures, which are believed to reflect alcohol mole fraction induced structural changes in these alcohol-water binary mixtures.

Excited state intramolecular charge transfer reaction of 4-(morpholenyl) benzonitrile in solution: Effects of hetero atom in the donor moiety

“…5 In one of our earlier studies on solute rotation in alcohol solvents, 21 a comparative study has shown that we could reliably measure a time constant of ~ 15 ps employing a time resolution of ~ 75 ps (see table 3 of ref. 21). We expect that this accuracy is also extended to the present measurements and thus reaction times ~ 20 ≥ τ rxn (ps) ≤ 50 are semi-quantitatively correct.…”

Fluctuating micro-heterogeneity in water–tert-butyl alcohol mixtures and lambda-type divergence of the mean cluster size with phase transition-like multiple anomalies

“…Examples of such non-ideal behavior in the binary mixture of water and amphiphilic solutes are varied and well-studied [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Sometimes the anomaly is strongest at surprisingly low solute concentrations.…”

Conductometric, spectrophotometric and thermodynamic studies of nickel sulfate in aqueous polyvinyl alcohol + methanol systems at different temperatures

“…In mixed solvent system decrease in hydration of ions also led to decrease in values of Kd. The effect of temperature on molar conductivity was shown by the Arrhenius relation [19,32].…”

“…The influence of various temperatures on conductivity measurement can give detailed information of ion-ion and ion-solvent interaction for different electrolytes solution [18][19][20][21][22][23][24][25][26][27][28][29][30]. Molecular associations in liquid system and their variations with composition and temperature were studied by thermodynamic data [31][32][33][34][35][36][37][38]. Transition metals occupy the space between group II and group III of the periodic table and due to their unique physical and chemical properties are of great interest.…”