Alkanol Chain Length Research Articles

Studies of viscosity and excess molar volume of binary mixtures: 2. Butylamine+1-alkanol mixtures at 303.15 and 313.15 K

The excess molar volume V E, viscosity deviation Δ η, excess viscosity η E, and excess Gibbs energy of activation Δ G* E of viscous flow have been investigated from the density ρ and viscosity η measurements of eight binary mixtures of butylamine with ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol and decanol over the entire range of mole fractions at 303.15 and 313.15 K. The viscosity data have been correlated with the equations of Grunberg and Nissan [L. Grunberg, A.H. Nissan, Nature 164 (1949) 799–800], Tamura and Kurata [M. Tamura, M. Kurata, Bull. Chem. Soc. Jpn. 25 (1952) 32–37], Hind et al. [R.K. Hind, E. McLaughlin, A.R. Ubbelohde, Trans. Faraday Soc. 56 (1960) 328–334], Katti and Chaudhri [P.K. Katti, M.M. Chaudhri, J. Chem. Eng. Data 9 (1964) 442–443], McAllister [R.A. McAllister, AIChE J. 6 (1960) 427–431], Heric [E.L. Heric, J. Chem. Eng. Data 11 (1966) 66–68], and of Auslaender [G. Auslaender, Br. Chem. Eng. 10 (1965) 196]. The systems studied exhibit very strong cross association through strong O–H⋯N bonding between –OH and –NH 2 groups. As a consequence of this strong intermolecular association, all eight systems have very large negative V E. Except butylamine+ethanol mixture, the magnitude of negative deviations in viscosity increases with chain length of alkanol.

Speeds of Sound, Isentropic Compressibilities, and Excess Molar Volumes of an Alkanol + Cycloalkane at 303.15 K. 1. Results for Alkan-1-ols + Cyclohexane

Isentropic compressibilities KS, excess isentropic compressibilities , and excess molar volumes VE have been determined from measurements of speeds of sound u and densities ρ of 10 binary mixtures of ethanol, propan-1-ol, butan-1-ol, pentan-1-ol, hexan-1-ol, heptan-1-ol, octan-1-ol, nonan-1-ol, decan-1-ol, and dodecan-1-ol with cyclohexane at 303.15 K over the whole mole fraction range. The values of decrease with number of carbon atoms of the alkanol going from positive values for ethanol + cyclohexane to negative for dodecan-1-ol + cyclohexane. The change of sign for occurs between hexan-1-ol and heptan-1-ol. The trend of decreasing with the chain length of alkanol is similar to that observed in case of VE. However, the VE values for all 10 mixtures of alkanol with cyclohexane are positive.

Excess Enthalpies and Excess Volumes of the Liquid Binary Mixtures of Propylene Carbonate + Six Alkanols at 298.15 K

The excess molar enthalpies and the excess molar volumes for binary mixtures of propylene carbonate with methanol, ethanol, 1- and 2-propanol, and 1- and 2-butanol have been determined as a function of composition at 298.15 K and atmospheric pressure, using an LKB flow microcalorimeter and an Anton Paar density meter. The excess enthalpies are positive for all mixtures, while excess volumes are negative for methanol and ethanol, positive for 1- and 2-butanol and show a change of sign, as a function of composition, for 1- and 2-propanol. Both excess properties increase in magnitude as the alkanol chain length increases. Results were correlated by means of the Redlich−Kister equation and a qualitative molecular interpretation is presented.

Phase Behavior, Transport Properties, and Thermodynamics of Water/AOT/Alkanol Microemulsion Systems

The phase diagrams of ternary systems of water/Aerosol-OT/alkanol (having carbon numbers 5, 6, 7, 8, and 10) are presented. Appreciable single-phase zones with viscous regions at higher proportions of AerosoI-OT (AOT) have been witnessed for all the alkanols. The ternary systems have also shown water-induced percolation of conductance with multistep phenomena in some cases. The viscous preparations have behaved like Bingham liquids (the viscosity has increased with the rate of shear). The enthalpy of the solubilization of water in alkanol/AOT medium has been calorimetrically determined to be positive; the free energy has been evaluated from the knowledge of maximum water intake until phase separation. The free energy and entropy of water solubilization (derived from Gibbs' equation) have been found to be positive and negative, respectively, and they follow a regular trend with the [alkanol]/[AOT] mole ratio ( R) as well as with the alkanol carbon number. On the other hand, the enthalpy values, although they increased with R , increase with alkanol chainlength to a maximum for heptanol and then decrease for both octanol and decanol. It is considered that the heptanol acts as an efficient cosurfactant with AOT and helps to produce microdroplets with increased endothermicity.

Short chain alkanols as transport enhancers for lipophilic and polar/ionic permeants in hairless mouse skin: Mechanism(s) of action

The influences of short chain n-alkanols (from C1 to C5) and isopropanol on the transport of lipophilic (β-estradiol and hydrocortisone) and polar/ionic (tetraethylammonium ion) permeants across hairless mouse skin have been investigated. Permeability studies employing a two-chamber diffusion cell were carried out over wide ranges of alkanol (in saline) concentrations with an aim toward quantifying the reversible enhancement effects of the added alkanol upon the lipoidal pathway of the stratum corneum. An enhancement factor, E (for the lipoidal pathway of the stratum corneum), was calculated from permeability coefficient and solubility data, and the E values for β-estradiol and for hydrocortisone were found to be nearly always the same in all instances. A pattern of increasing E values with increasing alkanol chain length up to C5 with these two permeants was found. A nearly semi-logarithmic linear relationship was also obtained between the enhancement potency and the carbon number of the n-alkanols; there was about 4-fold increase in the enhancement potency per n-alkanol methylene group. Pretreatment studies showed that the n-alkanol effetcts at low concentrations were reversible as far the lipoidal pathway of the stratum corneum was concerned. These results demonstrate the general usefulness of this approach for evaluating the action of enhancers on the barrier function of the stratum corneum. It is suggested that the short chain alkanols may work at low concentrations as effective ‘fluidizing’ agents at some locus in the stratum corneum lipid bilayer at or near the polar head plane, but not in the deep bilayer hydrocarbon interiors.

Transdermal controlled administration of indomethacin. I. Enhancement of skin permeability.

It was observed experimentally that indomethacin delivered in an aqueous suspension has a greater skin permeation rate in an ionized form than in a nonionized form. In this investigation, a matrix-type transdermal drug delivery system was developed to deliver indomethacin molecules in nonionized form. The skin permeation rate of nonionized indomethacin molecules from this system could be substantially improved by incorporating skin permeation enhancers, such as straight-chained alkanols, alkanoic acids, and esters. These enhancers form microreservoirs with indomethacin in the lipophilic silicone polymer matrix. By varying the alkyl chain length of alkanol, alkanoic acid, and its ester, the concentration of permeation enhancer, or the loading dose of indomethacin in the polymer matrix, the skin permeation rate of nonionized indomethacin molecules can be enhanced by as much as 30 times, which is almost sevenfold greater than the rate for ionized indomethacin molecules.

Alkanol effects on early potassium currents in Aplysia neurons depend on chain length.

The relationship between alkanol chain length and effects on the transient potassium current, IA, were examined in three identified Aplysia californica neurons with ethanol (EtOH), butanol (BuOH), and hexanol (HxOH). Qualitative differences were found when the actions of EtOH were compared with those of the longer-chain-length alcohols. Whereas EtOH primarily affected the decay time constant of IA, having minimal effects on amplitude, BuOH and HxOH exerted their major effect on the amplitude of IA, reducing it, while their effects on decay kinetics were much less pronounced. The effects of EtOH on IA decay are cell specific among identified neurons of the Aplysia nervous system. The actions of BuOH and HxOH did not mimic these interneuronal differences. These data, coupled with data previously reported by us and others, make it unlikely that EtOH exerts its actions on IA via perturbation of a bulk lipid phase within the membrane.

Dynamic properties of micellar solutions: I. Effects of short-chain alcohols and polymers on micellar stability

The effect of n-alkanols from C1 to C5 on both equilibrium and dynamic properties of sodium dodecyl sulfate (SDS) micellar solutions has been investigated using electrical conductivity and pressure-jump methods. Methanol and ethanol were found to decrease the conductance of micellar solutions due to the lowering of dielectric constant of solvent. Higher alkanols from C3 to C5 may decrease or increase the conductance of micellar solutions depending on the concentration of SDS. At low surfactant concentration, a minimum of conductance was observed. This has been attributed to both effects of decrease in surfactant monomer concentration (CMC) and the increase in counterion dissociation of micelles upon the penetration of alcohols into micelles. At higher surfactant concentration, the conductance was found to increase directly due to the dominance of the latter effect. Unlike the complex change of conductance, the slow relaxation rate constant, 1/τ2, has been found to increase monotonically upon the addition of all alkanols except pentanol. The labilizing effect (i.e., decreasing τ2) of alkanols increases with increasing alkanol chain length from C1 to C3 and levels off at C4. The labilizing effect has also been found to vary with SDS concentration depending upon the mechanism of slow relaxation process. Based on the Aniansson and Wall theory, the labilizing effect of alkanols has been attributed to two factors: (1) the stabilization of micelle nuclei either due to a decrease of micelle nucleus size, or due to an increase of micelle nucleus population; (2) the decrease of activation energy for the formation of micelle nuclei. In view of the changes in both slow relaxation time and CMC upon the addition of alkanols, the concept of micelle stability has been discussed in terms of the “thermodynamic stability” and the “kinetic stability” of micelles. Finally, the effect of polymers on the slow relaxation process was also investigated. The slow relaxation rate constant 1/τ2 was found to increase by three orders of magnitude as the concentration of polyvinylpyrrolidone increased up to 8% (w/w). Based on the molecular model of polymer-micelle complex proposed by B. Cabane (J. Phys. Chem.81, 1639, 1977), the effect of polymer has been interpreted in terms of the polymer being the nucleating agent for micelle nuclei. The result verifies the concept that the rate-limiting step in micelle formation and dissolution process is the formation of micelle nuclei.

Modulation by n-alkanols of rat cardiac adenylate cyclase activity.

n-Alkanols (from methanol to decanol) have a biphasic effect on rat cardiac adenylate cyclase either basal or stimulated by GTP, GppNHp, NaF or hormones (isoproterenol, glucagon, secretin) in the presence of GTP. At high concentration, all the enzyme activities are inhibited. At low concentration, adenylate cyclase activity is either unchanged or potentiated depending on both the stimulus and the alkanols involved. Potentiation is due to an increase of maximum velocity with no change in the activation constant of the enzyme. Basal activity is unchanged as well as the isoproterenol- and glucagon-stimulated enzyme. The secretin-stimulated enzyme is potentiated. It is the guanyl nucleotide regulatory protein-mediated stimulation of adenylate cyclase which is mainly affected. An attempt was made to relate these effects on adenylate cyclase with physical parameters of the alkanols (partition coefficient). From the data obtained as a function of the alkanol chain-length and of temperature on the adenylate cyclase stimulated by GTP, GppNHp, NaF and permanently activated, it is concluded that the increase in efficacy observed in the presence of alkanol is due to an interaction with the protein moeity particularly with the guanyl nucleotide regulatory protein.

Cholesterol Solubility in Organic Solvents

The 37° cholesterol solubilities in over 50 solvents, including the homologousn‐alkanols through dodecanol and homologous ethyl carboxylates through the undecanoate, and the 37° β‐sitosterol solubilities in then‐alkanols through decanol are reported. Additionally, solubility data for cholesterol at 7, 17, and 27° in the alcohol series were obtained. These measurements allowed the calculation of heats of solution for cholesterol in the alkanols, which range from 7.5 kcal for methanol to 4.3 kcal for decanol and which tend to decrease, although irregularly, with increasing alkanol chain length. A solubility maximum in all of these series for both solutes was observed between a chain length of six and seven. A surprisingly irregular, odd‐even alternating solubility pattern was noted for cholesterol in the alkanols at all four temperatures. Experimental evidence indicated that this pattern was due to solvent‐induced crystalline changes, presumably solvate formation, in each alkanol solvent through C10. Overall, the solubility studies screened solvents for their utility in dissolving cholesterol and, thus, cholesterol gallstones. To these ends, some limited dissolution experiments were performed, which indicated that the solution rate is directly related to the measured solubility in organic solvents. The dissolution behavior is thus different from micellar bile salt solutions, in which a significant interfacial barrier controls kinetics.