Pentanol Isomers Research Articles

Extraction of alkanol isomers

The isomer effects on the equilibrium partition coefficients of the two propanol, the four butanol, and two of the pentanol isomers between water and immiscicle solvents are shown to be governed primarily by the abilities of the alkanols to donate and accept hydrogen bonds. These abilities depend directly on the number of methyl groups bonded to the carbon atom that carries the hydroxyl group. The overall partition coefficient, irrespective of the isomeric form, depends on the total number of carbon atoms in the alkanol via its molar volume

Transition of rodlike to globular micelles by the solubilization of additives

The solubilization of hydrocarbons is surfactant solutions of tetradecyltrimethylammonium bromide in the presence of equimolar amounts of sodium salicylate was studied using static and dynamic light scattering techniques. The solutions contain large entangled rodlike micelles and have a high solubilization capacity for hydrocarbons. With increasing amounts of solubilized aliphatic hydrocarbon the long rodlike micelles become shorter and are transformed to globular aggregates at a characteristic hydrocarbon concentration. The globular micelles increase in size until saturation is reached. Both the solubilization capacity and the transition concentration depend on the chain length of the solubilized hydrocarbon and decrease with increasing chain length. Hydrocarbons with more than 16 C atoms are not soluble enough to enforce the transformation of the rodlike aggregates. Branched hydrocarbons like i-octane or esters like ethylhexanoate behave in the same way as the corresponding n-alkane. A different situation is observed for the solubilization of some aromatic hydrocarbons. Above a certain concentration of solubilized hydrocarbon the single-phase solution separates into two phases before the rodlike micelles are transformed to globules. The two-phase system is transformed back to a single-phase solution with further increase of the hydrocarbon concentration. The phase separation corresponds to a condensation of the rodlike micelles to a coacervate phase. Aromatic hydrocarbons with longer aliphatic sidechains like n-butylbenzene behave more like aliphatic hydrocarbons; solubilization of such additives does not lead to the separation of a coacervate phase. The influence of the solubilization of four isomeric pentanols on the size of the micelles was also investigated. For all pentanols the lengths of the rods decrease with increasing additive concentration. For n-pentanol a phase boundary is reached before the rodlike aggregates are transformed to spheres, while for all other branched pentanols the rods are transformed to globules before the saturation concentration of the additives is reached. The experimental data are interpreted on the basis of simple geometrical considerations and the packing parameter of the surfactant molecules.

Velocity and damping of thermal phonons in isomeric alcohols

Polarized Mandelstam-Brillouin scattering data in isomeric pentanols (normal-pentanol and 2-methyl-2-butanol) are presented. Hypersonic velocity νs and absorption α/f 2 are measured as a function of temperature in the liquid phase. The experimental results indicate, for both the alcohols, a shear relaxation phenomenon in the GHz region. The shear relaxation times τs and the shear moduli G ∞, evaluated in the framework of visco-elastic theories, show a temperature dependence characteristic of strongly associated liquids in n-pentanol, whereas a more molecular behaviour is evidenced for 2-methyl-2-butanol.

Alcohol-assisted alkaline flooding for enhanced oil recovery

Alcohol additives were found to improve alkaline flood performance under certain conditions. Only crude oils that emulsified during alkaline flooding were more efficiently recovered with alcohol. Improved recovery with alcohol was attributed to modification of emulsion characteristics. Alcohol additives reduced emulsion viscosities and accelerated emulsion coalescence rates, which improved oil bank stability and promoted oil recovery. Oil recovery efficiency was affected by the chemical structure of the alcohol. Oil recovery generally improved with increasing molecular weight from methanol to butanol and then decreased for the less water soluble pentanol isomers. Alcohol additives were found to affect the interfacial shear viscosities (IFSV) and interfacial tensions (IFT) of crude oil/alkaline water systems. Improvements in recovery efficiency was found to correspond directly to reduced IFSV. Poor recovery was also related to elevated interfacial tensions.

Molecular association of pentanols in n-heptane II: Viscosities as a function of temperature covering low concentration range

Abstract Viscosities of binary mixtures of isomeric pentanols in n-heptane at various mole fractions, F (F = 0.025 to 0.600) have been measured in the low temperature range (T = 233 to 293 K) with an automatic viscometer operating in a closed system. The temperature dependence of viscosity has been found to follow a simple relation, thereby allowing for the calculation of Ev, the activation energy for viscous flow. The latter is very sensitive to changes in molecular associates, especially at low concentrations. The results show that at low concentrations small multimers dominate for both 1-pentanol and 2-pentanol. At high concentrations, while the former may associate to give large linear multimers; the latter may result in the formation of large cyclic multimers with a low dipole moment. For 3-pentanol and tert-pentanol, small multimers are likely to dominate at low concentrations and there is a change in the dominating multimers from a linear type to a cyclic one, with increasing concentration in the limit F

Temperature Effects on the Structure and Dynamics of Isomeric Pentanols by IR and Raman Spectroscopy

Abstract We present IR absorption, polarized and depolarized Raman scattering data in n-pentanol and in 2methyl-2butanol. The measurements, performed over a wide temperature range, concern the fundamental O—H stretching vibrations. The experimental results confirm that intermolecular H-bonding effects play the main role in determining the shape and the evolution with T of the spectra. The deconvolution of the polarized Raman spectra in symmetric bands gives useful information concerning the dynamical properties of these systems. The analysis of the frequency shifts, the broadenings and the relative intensity variations with respect to the isolated O—H stretching bands confirm the existence of molecular aggregates with different spatial and/or topological conformations. The close analogy found for appropriately reduced IR absorption and depolarized Raman spectra proves that a vibrational density of states (VDOS) for both alcohols exists. These spectral features can be rationalized in terms of cooperative m...

The critical temperatures of isomeric pentanols and heptanols

The critical temperatures of seven isomeric alcohols have been measured using the modified sealed tube method of Mogollon. The ampoule used in the Mogollon method was modified to allow easier handling and reproducible results to be obtained. The addition of an Apple IIe microcomputer to the apparatus made possible the recording of the temperature history of the fluid and the monitoring of successive meniscus disappearances and appearances with time. The critical temperatures were obtained by averaging the temperatures of meniscus disappearance and reappearance. The fill densities of the ampoules were approximately equal to the critical densities.

Molecular association and dynamics in n-pentanol and 2-methyl-2-butanol

Static dielectric constant, viscosity, density, ultrasonic and dielectric relaxation measurements are reported for two pentanol isomers (n-pentanol and 2-methyl-2-butanol) in a wide range of temperatures. The results show a different extent of H-bonds self-association in relation to the molecular geometry of the alcohol. The activation energies obtained from dielectric and ultrasonic studies are compared with those obtained from viscous flow. Such a comparison, together with the analysis of all the dielectric and ultrasonic relaxation data, show that in n-pentanol a correlation between viscosity and ultrasonic relaxation exists, while dielectric relaxation is not correlated with the other two processes. This finding has been rationalized in terms of different mechanisms. In 2-methyl-2-butanol a correlation between ultrasonic and dielectric relaxation processes has been observed. Additional contribution of ultrasonic absorption associated with isomeric internal rotational of the molecules has been assumed to explain the experimental data for this alcohol.

Enthalpies of vaporization of aliphatic C5 and C6 alcohols

New calorimetric enthalpies of vaporization were determined for eight isomers of pentanol and hexanol with an accuracy of 0.3 percent. The results were combined with literature values for aliphatic C1-C4 alcohols, and some qualitative conclusions were drawn regarding the variations in enthalpies of vaporization and in closely related properties with chain length, degree of branching, and OH-group position.

Prediction of adsorption isotherms of organic compounds from water on activated carbons: IV. Adsorbability of structural isomers of alcohols

In order to clarify the adsorbability of structural isomers, the Freundlich's adsorption constants of the isomers of butanol and pentanol were determined and correlated with various physical constants such as solubility in water, boiling point, and some topological indexes characterizing the molecular connectivity or branching. A good linear relationship is obtained between the adsorption constant and the connectivity index. If the adsorption data of several normal compounds for a given activated carbon are obtained, the adsorption isotherms of the isomers can be predicted from the molecular connectivity alone.

Electrical properties of quaternary Winsor IV phases (the so-called microemulsions), as correlated to phase diagram features. Influence of the chemical structure of the alcohol cosurfactant

Winsor IV phases (the so-called microemulsions) were made from water and benzene, using as the surface-active agent a fixed combination of potassium oleate with any one of the eight isomers of pentanol. It was shown that the electrical behaviour of the microemulsions can be correlated to phase diagram features, which are strongly influenced, other things being equal, by the chemical structure of the alcohol used as the cosurfactant. A discussion is given of what the results obtained imply regarding the structure of microemulsions and the phase-inversion phenomenon.

Interactions in water-alcohol mixtures: Conductance of lithium picrate in solutions of water and isomeric pentanols at 25�C

Conductance measurements of lithium picrate in solutions of water in n-pentanol, 2-pentanol, 3-pentanol, 2-methyl-1-butanol and 3-methyl-1-butanol have been carried out at 25°C. Ionic association and conductance were found to change with water content and with the molecular structure of the alcohols (i.e. position of the OH group and degree of branching of the alkyl chain). These results indicate that both conductance and ion pair formation are not the consequence of the simple motion of ions in the electrical field as required by the continuum model. A more realistic approach, involving the internal structure of the solvent mixtures, has been considered.

Static dielectric constant, viscosity, and structure of pure isomeric pentanols

Static dielectric constants, viscosities, densitites and refractive indices of 2-pentanol, 3-pentanol, 2-methyl-1-butanol, 3-methyl-1-butanol and 2-methyl-2-butanol were measured at 15, 25, 35 and 45°C. These results together with the previous data on n-pentanol have been analyzed in terms of the Kirkwood correlation factor g k and of the energy of activiation for viscous flow. With the exception of 2-methyl-2-butanol, g k was found to be greater than unity. These results show that the monomeric units of isomeric pentanols interact by means of hydrogen bonding to form dynamic structures essentially of two types: linear chains where co-association raises the total polarizability and cyclic dimers with nearly zero net dipole moment. Energies of activation for viscous flow as well as Kirkwood correlation factors correlate with the molecular parameters (i.e. position of OH group in the molecules, steric hindrance of alkyl chain etc.) of the alcohols. The implication of these parameters on the molecular association of the isomeric pentanols are discussed.

Setting up of a time domain spectroscopy experiment. Application to the study of the dielectric relaxation of pentanol isomers

Discusses the problems encountered in setting up a semi-automatic system of time-domain reflectometry, and presents some solutions. The study of the dielectric relaxation of some alcohols-with well-known absorption spectra-shows the validity of the system. As an application the authors have measured the main dielectric relaxation of pentanol isomers at 25 degrees C.

The pressure dependence of the static permittivity of pentanol isomers

The static permittivity and density of six isomers of pentanol have been measured at pressures up to 4000 kgf cm−2 over a temperature range from 20 to 50 °C. Kirkwood's g has been evaluated from the experimental results, and the relationship between its temperature and pressure dependence and the structure of the alkyl radical is discussed.

The proportion of 2-methylbutanol and 3-methylbutanol in some brandies and whiskies as determined by direct gas chromatography

Stationary phases suitable for the separation of 2-methylbutanol (“active” pentanol) and 3-methylbutanol (isopentanol) are discussed. The most suitable for the determination of these alcohols in potable spirits by direct injection of samples are diethyl tartrate and polyethylene glycol 200. Polyethylene glycol 200 is preferred because other congeners can be determined at the same time. With n-pentanol as an internal standard, 65 samples of cognac brandies, Scotch and other whiskies have been examined on one or other of these stationary phases. The sum of the two pentanol isomers determined separately agrees well with their determination as a single peak on polyethylene glycol 1500. The ratio of the concentrations of the isomers appears to be characteristic of the type of spirit.