Isomeric Octanols Research Articles

Shear-Modulus Investigations of Monohydroxy Alcohols: Evidence for a Short-Chain-Polymer Rheological Response

Liquids composed of small-molecule monohydroxy alcohols are demonstrated to display rheological behavior typical for oligomeric chains. This observation was made possible by rheological experiments in which more than seven decades in frequency and more than five decades on the mechanical modulus scale are covered. The singly hydrogen-bonded monohydroxy alcohols were chosen because they display significant, but surprisingly poorly understood effects of intermolecular association. Based on the present shear study, one can apply theoretical concepts of polymer science to understand the anomalous physical behavior of a wide range of hydrogen-bonded liquids.

Partial molar volumes of organic compounds in C8 solvents at 298.15 K

Limiting partial molar volumes of n-hexane, cyclohexane, ethyl ether, tetrahydrofuran, pentan-3-one and cyclopentanone in di- n-butyl ether, hexyl acetate and octan-2-ol were determined at 298.15 K from density measurements of dilute solutions carried out with a vibrating-tube densimeter. The solute–solvent interactions and the effects of the local organisation of the solvent around the solute molecules were discussed using the molar, void, and cavity volumes as different estimates of the intrinsic volume of the molecules. The analysis was then extended to the volumetric behaviour of the same solutes in octan-1-ol. The solvents examined interact with the solutes in different ways. The isomeric octanols show the most significant effects, possibly due to their H-bond donor nature. The solute–solvent interactions seem to prevail over the packaging effects in determining the volumetric behaviour of the solutes.

Excess molar enthalpies and excess molar volumes of (water+octan-1-ol or +octan-2-ol) at 298.15 K

The excess molar enthalpies and volumes have been determined for the binary system (water+octan-1-ol or +octan-2-ol) by means of direct calorimetric and densimetric measurements in the miscibility range. The experimental data were described through a Redlich-Kister type equation. For excess enthalpies a sigmoidal shape is predicted,while excess volumes are negative except for a little positive queue observed for(water+octan-1-ol) system at very low water content. Also the partial molar enthalpies of solution and the partial molar volumes of water in the two isomeric octanols at infinite dilution have been evaluated and discussed. A comparison is made between excess enthalpies and excess free energies calculated by the UNIFAC method.

Structural Relaxation and H Bonding in Isomeric Octanols and Their LiCl Solutions by Calorimetry

Isomeric octanols show a variety of dielectric behavior. At low temperatures, some behave as nonpolar liquids, others as polar liquids. This results from the extent of steric hindrance for intermolecular H bonding when the CH3 group is in the proximity of the OH group in the seven-membered −C−C− chain. Differential scanning calorimetric studies of nine isomeric octanols and LiCl solutions of two of them are reported here. These are discussed in terms of structural relaxation, glass transition temperature Tg, configurational contribution to the heat capacity ΔCp, and distribution of structural relaxation times parameter β. Tg of the isomers of octanols lies between 148 and 168 K, ΔCp between 35 and 82 kJ/mol, and β between 0.33 and 0.93. Those octanols that behave dielectrically as nonpolar liquids have a broader distribution of relaxation times, or lower β, than those isomers that behave dielectrically as highly polar liquids. Addition of 5 mol % LiCl increases Tg and ΔCp in the former case but decreases both in the latter case, and the distribution of relaxation times broadens in both cases. An analysis in terms of configurational contributions to Cp shows that steric hindrance of the OH group determines the H-bonded motifs formed in liquid octanols near their glass−liquid transition temperature.

Effect of ions on intermolecular association and sub-T g dielectric relaxation in isomeric octanols

The effect of ions on the H-bond association in 4-methyl-3, 2-methyl-1, and 2-methyl-6-heptanols has been studied from measurements of their dielectric properties in their pure state and their LiClO4 solutions over a temperature range from their glassy to a supercooled fluid state. The ions increase the equilibrium permittivity of 4-methyl-3 and decrease that of 2-methyl-1 and 2-methyl-6-heptanols. Ionic interaction breaks H bonds in their structures and converts ring dimers of virtually zero dipole moment to linear dimers or monomers for the 4-methyl-3 and converts chain n mers to shorter chains for the 2-methyl-1, and 2-methyl-6-heptanols, thus confirming our earlier interpretation of two types of H-bond association in isomeric octanols. The effect of ions on the permittivity and H-bond structure of 4-methyl-3 is similar to the effect of hydrostatic pressure and on those of 2-methyl-1 and 2-methyl-6-heptanols is opposite to that of hydrostatic pressure. On the addition of LiClO4, the height of the sub-Tg relaxation peak increases as does the permittivity at 100 K. The former is a reflection of less efficient molecular packing and the latter of an increase in the optical and infrared polarizabilities with increase in the LiClO4 concentration. Dielectric and conductivity measurements of ionic solutions are useful methods for studying the H-bond association in pure liquids.

TRIGLYCERIDE–METHANOL MICROEMULSIONS

ABSTRACT Even-numbered 1-alkanols from butanol to tetradecanol were evaluated for solubilizing and microemulsifying methanol in triolein and for their effectiveness on water tolerances of the hybrid fuels. Photon correlation spectroscopy determinations indicated molecular dispersions formed rather than nonaqueous microemulsions, but the addition of water to the solubilized systems did produce certain quarternary compositions that exhibited microemulsion properties. 1-Octanol imparted optimal, whereas 1-butanol and 1-tetradecanol imparted minimal, water tolerance for the hybrid fuels. Among four isomeric octanols studied, the 1- and 4-octanols were superior to the 2- and 3-octanols for water tolerance. This superiority is attributed to stronger hydrogen bonding and greater association in the 1-and 4-isomers compared to the 2- and 3-isomers.

Ultrasonic investigations of mixtures of n-octane with isomeric octanols. Isoentropic compressibility and excess volumes of mixing

Volumes of mixing, isoentropic compressibilities, acoustic attenuations and viscosities are reported on mixtures of various isomeric octanols and octane at 298.15 K. The data are interpreted in terms of competing effects of the alkane chain taking up the ‘free’ volume in the system and the disturbance of the distribution between cyclic and linear structures and monomer forms in the mixtures.

Lag phase during the action of phospholipase A2 on phosphatidylcholine modified by alkanols.

Theaction of pig pancreatic phospholipase A2 (EC 3.1.1.4) on phosphatidylcholine bilayer is studied under a variety of substrate modification conditions including the incorporation of long chain alcohols (hexanol and several isomeric octanols) into the bilayer. The rate of hydrolysis shows a biphasic dependence upon the concentration of the activating alcohol. The hexanol to lipid molar ratio in the bilayer is approximately 1.4:1 at the optimal alkanol concentration. The lag phase at the beginning of hydrolysis has been shown to depend upon the nature of the bilayer as modified by different alkanols and by intrinsic differences in the unilamellar vesicles (approximate diameter approximately 250 A) compared to the multilamellar vesicles. The rate constant for the activation process responsible for the lag period is first order and does not depend upon the concentration of the enzyme, substrate, alkanol, and calcium. These and other experiments are interpreted in terms of a hypothesis that the pancreatic phospholipase interacts with the bilayer by a catalytic and a recognition site. The data suggest that the packing of the interface regulates the interaction of both the catalytic and the recognition site. It is postulated that the biphasic activation profile as a function of hexanol concentration may be a consequence of two-site interactions between the enzyme and the substrate interface.

Viscous Liquids and the Glass Transition. III. Secondary Relaxations in Aliphatic Alcohols and Other Nonrigid Molecules

The dielectric permittivity and the dielectric loss factor of 5-methyl-3, 4-methyl-3 and 3-methyl-3-heptanol, n- and iso-butanol, 1,2-propanediol, dimethyl and diethyl phthallate, and 3-methylpentane have been measured from 50 to 105 Hz and from −196 to about 20°C above their respective glass transition temperatures. The glass transition temperature Tg of these substances, several more isomeric octanols, and 1-phenyl-1-propanol have been measured by differential thermal analysis. All substances except for 3-methylpentane and iso-butanol show either a well-defined secondary relaxation peak in tanδ, or a clear indication of the presence of a secondary relaxation below their Tg's. Arrhenius plots for the α-relaxation process of the isomeric octanols are linear with an activation energy of 16–18 kcal/mole, while for other substances they are nonlinear with the activation energy changing from 30 to 70 kcal/mole. The Arrhenius plots for the secondary relaxations are linear and have an activation energy of 4–8 kcal/mole. It is pointed out that the presence of a spectrum of relaxation times in liquids near Tg is not necessarily concomitant with non-Arrhenius behavior. It is concluded that the presence of secondary relaxations should be considered as a characteristic property of the liquid in or near the glassy state, and do not require specific intramolecular mechanisms for their existance.

Liquid structure and dielectric relaxation of some isomeric methylheptanols

Abstract The dielectric permittivity and loss of 6-, 4-, and 2-methyl-1-heptanol have been measured over a wide range of frequency and temperature. The equilibrium polarization of all three isomers and its temperature dependence is similar, which suggests that the type and extent of intermolecular association is also similar. A model of H-bond association to chain n-mers is proposed. Dielectric relaxation is Debye-like for all three liquids; the activation parameters are shown to be sensitive functions of the isomer structure. A qualitative model of relaxation in which H-bond rupture is a prerequisite rather than a rate determining step is proposed. Relaxation in other isomeric octanols and monoalcanols is discussed from this point of view.

Effect of Pressure on Dielectric Relaxation in Isomeric Octanols

Dielectric constant and loss have been measured in the frequency range 0.1 − 5 × 106 Hz over a wide range of temperature and pressures to 4 kbar for the following compounds: 2-octanol, 7-methyl-, 6-methyl-, 5-methyl-, and 2-methyl-3-heptanol. For each compound, most of the dispersion is well described by the Debye equation. At high frequencies additional regions of dispersion appear which could be resolved in three of the compounds. Activation parameters are derived for all of the compounds and are functions of pressure, temperature, and the nature of the alcohol's alkyl group. A qualitative model of dielectric relaxation based on ideas of Litovitz and Anderson and Ullman is proposed to explain the results.

Dielectric Relaxation in Isomeric Octyl Alcohols

The dielectric constant and loss of eight isomeric octanols has been measured over a wide range of temperature and frequency. Two distinctly different types of dispersion loci are found: For those alcohols whose –OH group is so sterically hindered that association into linear chains is unfavorable, a very small, very broad dispersion, characterized by relatively short relaxation times, is found. For less hindered species, the low-frequency, relatively slow, dispersion is Debye-like, and two high-frequency dispersion regions have been resolved in two compounds. The molar activation energies for all three dispersion regions are closely similar and τ1:τ2:τ3 ∼ 100:10:1. The activation energy for the principal (Debye-like) dispersion is strongly dependent on the steric hindrance of the –OH group. Activation energies vary from about 8 to 20 kcal so that rupture of a hydrogen bond is an unlikely rate-determining step.

Dielectric Study of Intermolecular Association in Isomeric Octyl Alcohols

The equilibrium dielectric constants of eight liquid isomeric octanols have been measured over a wide range of temperature, and the data are analyzed in terms of the Kirkwood correlation factor. A simple molecular model based on hydrogen-bond associative equilibria involving both ring dimers and linear chain n-mers is developed. Equilibrium constants for ring and chain formation are deduced, and it is concluded that entropic factors, which can be correlated with the geometry of the molecules, are the principal basis for differences between isomers. At relatively high temperatures those species whose − OH group is most sterically blocked prefer to form rings, while those whose − OH group is relatively accessible tend to form open chains. In all cases, chains become the preferred species at low temperatures. ΔH° for hydrogen-bond formation in chains is estimated as about − 6.7 kcal/mole; for rings, about − 4.5 kcal/mole. ΔS° varies from − 16 to − 30 eu/mole for chains and from − 13 to − 20 eu/mole for rings.

Structure—Property Relationships in Some Isomeric Octanols

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructure—Property Relationships in Some Isomeric OctanolsG. L. Dorough, H. B. Glass, Thos. L. Gresham, G. B. Malone, and E. Emmet ReidCite this: J. Am. Chem. Soc. 1941, 63, 11, 3100–3110Publication Date (Print):November 1, 1941Publication History Published online1 May 2002Published inissue 1 November 1941https://doi.org/10.1021/ja01856a064RIGHTS & PERMISSIONSArticle Views151Altmetric-Citations34LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (991 KB) Get e-Alerts Get e-Alerts