Series Of Normal Alcohols Research Articles

Compressibility and Dielectric Relaxation of Mixtures of Water with Monohydroxy Alcohols.

Isentropic compressibility data and principal dielectric relaxation times, mostly for normal alcohols and for mixtures of monohydroxy alcohols with water, are evaluated and compared to one another. It is found that the microdynamics of the liquids, as reflected by the dielectric relaxation times, can be generally explained in the light of a defect diffusion model. Within the framework of that model, the principal relaxation time is predominantly controlled by the local concentration of hydrogen bonding sites. The alkyl groups of the alcohols are shown to have a 2-fold influence by reducing the concentration of the H-bonding sites and by also contributing to the activation enthalpy of relaxation. The effect of alkyl groups on the compressibility is quite different. The compressibility of methanol exceeds that of water by a substantial amount. Within the series of normal alcohols, in correspondence with the behavior of normal alkanes, the liquids become less compressible with increasing alkyl chain length. Relative molal shifts Bκ and Bd of the compressibility and dielectric relaxation time, respectively, of dilute solutions of alcohols in water are consistent with the behavior of aqueous solutions of other organic solutes. The Bd values increase with hydrophobic character of the solute (ΔBd = 0.045 (mol/kg)(-1) for an additional methyl group per solute molecule or organic ion), whereas Bκ decreases (ΔBκ = -0.012 (mol/kg)(-1)). Reduced orientational mobility combined with decreased compressibility appears to be characteristic of hydration shells around hydrophobic solutes.

Effects of solute mass transfer on the stability of capillary jets

The effects of mass transfer (e.g. via evaporation) of surface-active solutes on the hydrodynamic stability of capillary liquid jets are studied. A linear temporal stability analysis is carried out yielding evolution equations for systems satisfying general non- linear kinetic adsorption relations and accompanying surface constitutive equations. The discussion of the instability mechanism associated with the Marangoni effect clarifies that solute transfer into the jet is destabilizing whereas transfer in the opposite direction reduces instability. The general analysis is illustrated by a system satisfying Langmuir-type kinetic relations. Contrary to a clean system (i.e. in the absence of surfactants), reduced jet viscosity may lead to a substantial reduction in perturbation growth. Furthermore, the Marangoni effect gives rise to an overstability mechanism whereby perturbations whose dimensionless wavenumbers exceed unity grow with time through oscillations of increasing amplitude. The common diffusion-control approximation constitutes an upper bound which substantially overestimates the actual growth of perturbations. Considering solutes belonging to the homologous series of normal alcohols in water–air systems, the intermediate cases (e.g. hexanol–water–air which is ‘mixed-control’) are the most susceptible to Marangoni instability.

Electrochemical and surface enhanced Raman scattering studies of bromide ion adsorption at silver electrodes in a series of normal alcohols

Br- surface coverage as a function of electrode potential is quantitatively determined using the Hurwitz–Parsons analysis of differential capacitance data at Ag electrodes in the series of normal alcohols, methanol through pentanol, containing LiBr. Values for the potential of zero charge (pzc) are estimated from these data. Surface-enhanced Raman spectroscopy (SERS) data in the ν(Ag–Br) region show the presence of a ν(Ag–Br) feature at potentials positive of the pzc which supports strong specific adsorption of Br- in these media. An excellent correlation between the SERS intensity and the Br- surface coverage determined from differential capacitance is observed. Bands attributed to hindered translational modes of trace interfacial water are also observed.

Investigation of trace interfacial water at silver electrodes in a series of normal alcohols using surface enhanced Raman scattering

The behavior of trace interfacial water and its interaction with Li+ and Br- ions at Ag electrodes in the series of alcohols, methanol, ethanol, propanol, butanol and pentanol is studied using surface-enhanced Raman scattering (SERS). SERS spectra in the ν(O–H) region exhibit four bands from the interfacial water species which are a sensitive function of the nature of the solvent, the residual water concentration and the electrode potential. These bands are assigned to water species interacting with specifically adsorbed Br-, Li+ in the outer Helmholtz plane, “free’' water species in the interface, or hydroxide in LiOH microcrystallites precipitated onto the electrode surface. Interfacial water molecules cluster around Li+ and Br- ions. The spectral data suggest pronounced restructuring of the water in the interface in the vicinity of the potential of zero charge.

Effect of solvent polarity on a rotational isomerization mechanism of rhodamine-B in normal alcohols

Experiments were performed to investigate the effects of solvent polarity and solvent viscosity on the nonradiative rates of rhodamine-B in a series of normal alcohols. The fluorescence quantum yields and lifetimes for rhodamine-B in these solvents were measured and used to calculate the nonradiative rates. From a modified kinetic model, the nonradiative rate can be deduced to be the conversion rate for crossing over a potential barrier from an excited planar state to an excited twisted state. Both solvent viscosity and solvent polarity can play key roles in this mechanism because the former may hinder the rotational motion and the latter may change the barrier height. Our results show that the variation in the nonradiative rates is due to solvent polarity changes rather than to solvent viscosity changes. The effect of solvent viscosity on the excited-state lifetimes of rhodamine-B in a series of methanol–poly(ethylene oxide) mixed solvents was also investigated. Our results indicate that the measured lifetimes are essentially independent of solvent viscosities, which in turn indicates that solvent viscosities have no significant effect on the nonradiative rates.

Effect of solvent polarity on nonradiative processes in xanthene dyes: Rhodamine B in normal alcohols

The fluorescence lifetime of rhodamine B in a series of normal alcohols (C/sub n/H/sub 2n-1/OH, n = 1-6) was measured as a function of temperature. The nonradiative rate constants were calculated from the fluorescence lifetimes and quantum yields. Activation energies were obtained from Arrhenius plots of the nonradiative rate constant. The variation of the nonradiative rate constant with solvent polarity and temperature was consistent with a photophysical mechanism that involves equilibrium between the planar and twisted configurations of the diethylamino groups on the xanthene ring of rhodamine B and internal conversion from the twisted configuration. The activation energy is equal to the free energy difference between the twisted and planar configurations. The solvent polarity dependence of the free energy difference and of the rate constant for internal conversion from the twisted configuration determines the variation of the nonradiative rate constant with solvent. When solvent polarity effects are taken into account by using the parameter E/sub T/(30), the nonradiative rate constant shows weak or no dependence on the solvent viscosity.

Complexes of short-chain alcohols with?-cyclodextrin

The complex formation of β-cyclodextrin with short chain aliphatic alcohols has been studied. The stability constants of 1∶1 complexes, determined spectrophotometrically, increase monotonically in the series of normal alcohols, while branching in the chain results in a further increase in stability. With smaller monoalcohols, complexes containing more than one guest molecule are formed as well, but the relative stability of these complexes decreases with increasing chain length and branching. The stabilities of 1∶1 complexes decrease with an increasing number of OH-groups, probably due to a stronger hydration. This reflects both the roles of space filling and hydrogen bridging

Extended Solubility Approach: Solubility Parameters for Crystalline Solid Compounds

A method is suggested to obtain solubility parameters for crystalline solid compounds, involving a quadratic equation based on the original Scatchard-Hildebrand solubility expression. The geometric mean, δ1δ2, of the Hildebrand approach is replaced by w12 = Kδ1δ2, and log α2/(V2ø22/2.3RT) is regressed against δ1 in a second-degree power series for parabens and benzoic acid in a series of normal alcohols. The method provides reasonable solubility parameters for the solid solutes and affords a convenient calculation of the solubility of drugs in a homologous series of solvents.

Effects of local anaesthetics on intracellular fusion processes. Enhancement of concanavalin A-induced macrophage vacuolation

The extensive vacuolation elecited in mouse peritoneal macrophages in response to interaction with concanavalin A is markedly enhanced by a simultaneous exposure to anaesthetics. The potency of enhancing vacuolation increases within the series of normal alcohols with chain length C 10 > C 8 > C 7 > C 6. From the four tertiary amine local anaesthetics tested lidocaine and procaine are by far more effective than tetracaine and dibucaine. The latter two induce extensive cell shrinkage at concentrations at which the first two exhibit optimum enhancing capacity. Of the tested compounds chlorpromazine has the highest membrane/buffer partition coefficient and it exhibits its optimum enhancing effect on concanavalin A-induced macrophage vacuolation at the lowest drug concentration. The binding of [ 3H] concanavalin A as well as its internalization by macrophages incubated with the lectin for 15, 45 and 90 min are not affected significantly in the presence of decanol, procaine or chlorpromazine at concentrations of maximum enhancing effect on vacuolation. Thus enhancement of vacuolation does not stem from an increase in the rate or extent of concanavalin A interiorization. The rate at which vacuoles are generated is however markedly increased in the presence of chlorpromazine and the resulting vacuoles are of a larger diameter. At 2–5 fold the concentration required for inhibition of maximum enhancing effect, the drugs lead to extensive macrophage shrinkage and to depletion of intracellular ATP. Phagocytosis of heat-killed yeast cells is reduced by tertiary amine anaesthetics at concentrations optimal for enhancement of concanavalin A-induced vacuolation. Enhanced intracellular fusion of concanavalin A-bearing pinosomes to form vacuoles is discussed in terms of current ideas on factors affecting membrane fusion and the effects of anaesthetics on membrane organization of lipids, intramembraneous particles, glycoprotein receptors and the possible control by cytoskeletal elements. The results best fit the hypothesis that enhanced fusion correlates with membrane aggregation of both intramembraneous particle and concanavalin A receptor and the formation of areas relatively deplete of these structures and enriched in phospholipids.

Studies of effects of hydrogen bonding on orientational relaxation using picosecond light pulses

Orientational relaxation of rhodamine 6G in a series of normal alcohols, ethylene glycol, chloroform and formamide has been studied using picosecond light pulses. The effects of hydrogen bonding and the structure of the liquids on the molecular rotational motion are examined.

Observation of structural effects in liquid and solid alcohols near their solidification temperatures using electron spin resonance

The hyperfine spectra of 10-4 M solutions of DPPH in each of a series of normal alcohols, methanol to decanol inclusive, have been studied to as a function of temperature. A characteristic well- defined change occurs in each case near the melting point and the five-line structure is replaced by three lines. The reduction occurs in the liquid for highly associated alcohols, ethanol to heptonal inclusive, and in the solid for methanol, octanol and the higher alcohols. It is proposed that the spectral change is due to an ordered 'liquid' structure arising from the OH groups, whether the alcohol is liquid or solid.

Solubility of Parabens in Alcohols

The solubilities of methyl, ethyl, propyl, and butyl parabens have been determined in a series of normal alcohols. This pure solvent scan indicated a dielectric requirement of about 14 for the subject compounds. Another dielectric requirement may be postulated to exist at a value of about 30. There is seen to be good parallelism in the magnitude of solubility of these compounds in various 1-alkanols indicating interactions of a similar nature in the dissolution process.