Presence Of Short-chain Alcohols Research Articles

Decomposition mechanism of α-alkoxyalkyl-hydroperoxides in the liquid phase: temperature dependent kinetics and theoretical calculations.

Organic hydroperoxides (ROOHs) play key roles in the atmosphere as a reactive intermediate species. Due to the low volatility and high hydrophilicity, ROOHs are expected to reside in atmospheric condensed phases such as aerosols, fogs, and cloud droplets. The decomposition mechanisms of ROOHs in the liquid phase are, however, still poorly understood. Here we report a temperature-dependent kinetics and theoretical calculation study of the aqueous-phase decompositions of C12 or C13 α-alkoxyalkyl-hydroperoxides (α-AHs) derived from ozonolysis of α-terpineol in the presence of 1-propanol, 2-propanol, and ethanol. We found that the temporal profiles of α-AH signals, detected as chloride-adducts by negative ion electrospray mass spectrometry, showed single-exponential decay, and the derived first-order rate coefficient k for α-AH decomposition increased as temperature increased, e.g., k(288 K) = (5.3 ± 0.2) × 10−4 s−1, k(298 K) = (1.2 ± 0.3) × 10−3 s−1, k(308 K) = (2.1 ± 1.4) × 10−3 s−1 for C13 α-AHs derived from the reaction of α-terpineol Criegee intermediates with 1-propanol in the solution at pH 4.5. Arrhenius plot analysis yielded an activation energy (Ea) of 12.3 ± 0.6 kcal mol−1. Ea of 18.7 ± 0.3 and 13.8 ± 0.9 kcal mol−1 were also obtained for the decomposition of α-AHs (at pH 4.5) derived from the reaction of α-terpineol Criegee intermediates with 2-propanol and with ethanol, respectively. Based on the theoretical kinetic and thermodynamic calculations, we propose that a proton-catalyzed mechanism plays a central role in the decomposition of these α-AHs in acidic aqueous organic media, while water molecules may also participate in the decomposition pathways and affect the kinetics. The decomposition of α-AHs could act as a source of H2O2 and multifunctionalized species in atmospheric condensed phases.

Formation of sacha inchi oil microemulsion systems: effects of non-ionic surfactants, short-chain alcohols, straight-chain esters and essential oils.

This study reports the formation of sacha inchi oil (SIO) microemulsions for food and cosmetic applications. Effects of non-ionic surfactants, short-chain alcohols, essential oil and straight-chain esters on the phase behavior and formulation of U-type microemulsion were investigated. Pseudo ternary phase diagrams were constructed to assess the influence of these factors using water titration method. Structural transitions were measured along several water dilution lines using conductivity and viscosity tools. Among four different surfactants, Tween 80 solubilized the maximum oil and induced the formation of a U-type microemulsion system. Oil solubilization was decreased in the presence of short-chain alcohols. In addition, the system containing straight-chain esters as the cosolvent showed a higher expansion effect in the U-type areas than that containing essential oils. Finally, upon water dilution of three systems with SIO/ethyl acetate of 1:1, 1:2 and 1:3, microstructural transition from W/O to bicontinuous occurred at 200 g kg-1 (w/w) water content, and then to O/W structure at 650 g kg-1 (w/w) water content. Straight-chain esters as cosolvent is a potential strategy to extend the dilutability of SIO microemulsions. © 2021 Society of Chemical Industry.

Impacts of Organic Sorbates on the Ionic Conductivity and Nanostructure of Perfluorinated Sulfonic-Acid Ionomers

This study provides insights into structure-property relationships of Nafion membranes swollen with organic sorbates, revealing correlations between sorbate polarity, ionomer domain structure, and ionic conductivity. Swelling, nanostructure, and ionic conductivity of Nafion in the presence of short-chain alcohols and alkanes was studied by infrared spectroscopy, X-ray scattering, and voltammetry. Nafion equilibrated with alkanes exhibited negligible uptake and nanoswelling, while alcohols induced nanoscopic- to macroscopic- swelling ratios that increased with alcohol polarity. In mixed-sorbate environments including organics and water, alcohols preserved the overall ionomer domain structure but altered the matrix to enable higher sorbate uptake. Alkanes did not demonstrably alter the hydrated nanostructure or conductivity. Identifying the impacts of organic sorbates on structure-property relationships in ionomers such as Nafion is imperative as membrane-based electrochemical devices find applications in emerging areas ranging from organic fuel cells to the synthesis of fuels and chemicals.

Amyloid formation of bovine insulin is retarded in moderately acidic pH and by addition of short-chain alcohols

Protein aggregation and amyloid formation are associated with multiple human diseases, but are also a problem in protein production. Understanding how aggregation can be modulated is therefore of importance in both medical and industrial contexts. We have used bovine insulin as a model protein to explore how amyloid formation is affected by buffer pH and by the addition of short-chain alcohols. We find that bovine insulin forms amyloid fibrils, albeit with different rates and resulting fibril morphologies, across a wide pH range (2–7). At pH 4.0, bovine insulin displayed relatively low aggregation propensity in combination with high solubility; this condition was therefore chosen as basis for further exploration of how bovine insulin’s native state can be stabilized in the presence of short-chain alcohols that are relevant because of their common use as eluents in industrial-scale chromatography purification. We found that ethanol and isopropanol are efficient modulators of bovine insulin aggregation, providing a three to four times retardation of the aggregation kinetics at 30–35% (vol/vol) concentration; we attribute this to the formation of oligomers, which we detected by AFM. We discuss this effect in terms of reduced solvent polarity and show, by circular dichroism recordings, that a concomitant change in α-helical packing of the insulin monomer occurs in ethanol. Our results extend current knowledge of how insulin aggregates, and may, although bovine insulin serves as a simplistic model, provide insights into how buffers and additives can be fine-tuned in industrial production of proteins in general and pharmaceutical insulin in particular.

Transformation of Glucose into Sorbitol on Raney Nickel Catalysts in the Absence of Molecular Hydrogen: Sugar Disproportionation vs Catalytic Hydrogen Transfer

Raney nickel catalysts have been tested in the transformation of glucose into sorbitol through a hydrogen transfer pathway in the presence of short chain alcohols. Comparison between different sacrificing alcohols evidenced that catalytic hydrogen transfer (CHT) was only possible from ethanol under the tested neutral conditions. Catalytic tests showed that together with CHT route, sorbitol was also produced by means of sugar disproportionation, with the simultaneous production of gluconolactone, which takes place easily in the presence of the Raney Ni catalysts. Studies on the influence of the catalyst loading on the production of sorbitol revealed the existence of a catalyst activation step, attributed to the generation of metal-hydride species, the truly catalytic sites for hydrogenation. However, a catalyst deactivation phenomenon was detected as well. In this case, TGA and FTIR analysis allowed ascribing the adsorption of organic species, coming from the oxidation of glucose (such as gluconic acid), onto the catalyst surface, to the most plausible cause for the deactivation of the catalyst. Catalyst recycling tests evidenced the deactivation occurred mainly during the first use of the Raney Ni catalyst.

Clouding Behaviour of Polysorbate 80: Effect of Additives

AbstractPolysorbate 80 and sodium lauryl ether sulphate mixtures are often used in personal care products especially in shampoo formulations. In this paper, the combined effect of sodium lauryl ether sulphate and salts (Na2SO4, NaCl, CaCl2) and sodium lauryl ether sulphate and alcohols having different chain length on the cloud point of polysorbate 80 has been studied. The cloud point of a nonionic surfactant is influenced by the presence of additives. In the current system, a rise in the cloud point of polysorbate 80 was observed in the presence of ionic surfactant, sodium lauryl ether sulphate (0.010–0.050 mM) which is interpreted as increase in the surface charge of micelle. The cloud point of the sodium lauryl ether sulphate-polysorbate 80 mixture decreased with the addition of inorganic salts. The presence of short chain alcohols (C1–C3) was found to increase the cloud point of polysorbate 80-sodium lauryl ether sulphate mixtures whereas, long chain alcohols (C4, C5) were found to decrease the cloud point of polysorbate 80-sodium lauryl ether sulphate mixtures depending on their solubility in water.

Behavior of cetyltrimethylammonium bromide and Triton X-100 mixture at solution–air interface in presence of short-chain alcohols

Surface tension measurements of the aqueous solutions of cetyltrimethylammonium bromide (CTAB) and Triton X-100 (TX-100) mixture with methanol or propanol in the whole range of alcohol concentration and in the range of surfactant mixture concentration from 1×10−6 to 1×10−3M were carried out. Based on the obtained results, the surface excess concentration values of this mixture and alcohols were calculated from the equation of Gibbs adsorption isotherm as well as from the Guggenheim-Adam one. Applying these surface excess concentration values, the composition of the mixed surface layer was established and compared with the hypothetic monolayer determined from the surface excess concentration values of the surfactant mixture and alcohols on the assumption that their adsorption was independent. The composition of the TX-100 and CTAB mixture was also calculated from the Rosen et al. concept on the assumption that water+alcohol was a mixed solvent and compared to the composition of the mixed monolayer formed from the independent adsorption of TX-100 and CTAB. From this comparison it results that there is a synergism in the reduction of the water surface tension at a certain composition of the surfactant mixture in the presence of alcohols. This synergism was confirmed by the standard free energy of the surfactant mixture adsorption calculated from both the Langmuir equation and the excess Gibbs free energy of TX-100 and CTAB mixing in the monolayer in the presence of methanol or propanol.

Room temperature ordering of dipalmitoyl phosphatidylserine bilayers induced by short chain alcohols

Using differential scanning calorimetry and small and wide angle X-ray diffraction, we show that, following extended incubation at room temperature, methanol, propanol, and three of the isomers of butanol can induce ordering in dipalmitoyl phosphatidylserine (DPPS) gel phase bilayers. The organization of the bilayers in the presence of ethanol, described previously, is now observed to be a general effect of short chain alcohols. Evidence is presented for tilting of the acyl chains with respect to the bilayer normal in the presence of ethanol or propanol. However, the different chain lengths of the alcohols, and isomeric form, influence the thermal stability of the ordered gel to different extents. This behavior is unlike that of the gel state phosphatidylcholine analog which, in the presence of short chain alcohols, undergoes hydrocarbon chain interdigitation. Dipalmitoyl phosphatidylcholine added to DPPS in the presence of 20vol% ethanol, acts to suppress the ordered gel phase.

Light scattering and NMR studies of Triton X-100 micelles in the presence of short chain alcohols and ethoxylates

Micellar characteristics of nonionic surfactant p-tert-octyl-phenoxy polyethylene (9.5) ether (Triton X-100) in aqueous media containing short-chain alcohols and their ethoxylates CnEm (n=2, 4, 6 and m=0, 1, 2) were examined by dynamic light scattering (DLS) and nuclear magnetic resonance (NMR). The micelle size increased with the addition of C6Em and decreased when C2Em alcohols were added to Triton X-100 solution; the increase and decrease in the micellar size in the presence of varying amounts of C4Em alcohols depends on the number of polar ethoxylate groups. The results are supported by viscosity and cloud point data and explained on the basis of solvophobic interaction. The interaction and location of additives in micelles is examined by 1H and NOESY NMR. The studies indicate that C2Em molecules mostly remain in bulk water; C6Em molecules get solubilized toward the core of the aggregates, while C4Em molecules are localized in the shell region of micelle according to their octanol/water partition coefficient values.

Chemiluminescence parameters of peroxynitrous acid in the presence of short-chain alcohols and Ru(bpy)32+

AbstractThe chemiluminescence behaviour and mechanism of peroxynitrous acid and Ru(bpy)32+ were studied in the presence of short-chain alcohols (methanol, ethanol, propan-1-ol, propan-2-ol, butanol, 2-methylpropan-1-ol, pentanol). It was found that the chemiluminescence intensity of peroxynitrous acid and Ru(bpy)32+ system could be significantly enhanced by these seven short-chain alcohols. The maximum chemiluminescence wavelength of 608 nm of [Ru(bpy)32+]* in the excited state was attributed to the reaction between Ru(bpy)32+ and dihydroxyalkyl radicals which were generated during the redox course of peroxynitrous acid and alcohols. In addition, the chemiluminescence signals of the system presented depended largely on the solubility and branched-chain structure as well as the length of carbon chain. The analytical characteristics and parameters of the peroxynitrous acid/Ru(bpy)32+/alcohols chemiluminescence system were investigated under optimum conditions.

アルコールによるリポソーム膜の指組み構造相の形成に関する研究

It was now well established that phosphatidylcholines or phosphatidylglycerols can form an interdigitated structural phase (Iphase), in which acyl chains of the lipids fully interpenetrate the hydrocarbon chains of the opposing monolayer in the presence of short chain alcohols and some other amphiphiles. It has been suggested that the interdigitated structure as well as a hexagonal II structure plays an important role in regulating many functions of biological membranes. We have demonstrated the participation ofIphase formation in ethanol-induced liposomal aggregation and fusion. We have also focused on control of permeability as one of the biomembrane functions, and the effects of ethanol on the permeability of large unilamellar vesicles composed of various phospho-lipids were studied by monitoring the leakage of the fluorescent dye, calcein, entrapped in the inner aqueous phase of the vesicles. In the cases of mixed membranes composed of DPPC and dilauroyl phosphatidylethanolamine (DLPE), as well as DPPC liposomal membranes, large permeabilities were observed in the wide range of ethanol concentrations, where the normal bilayer andIphase coexist and the membrane is in a phase-separated state. These results suggested that ethanol can disturb the normal control of biological membrane permeability.

Enhanced permeation of polar compounds through human epidermis. I. Permeability and membrane structural changes in the presence of short chain alcohols

The influence of alcohol chain length on polar compound permeation in human skin was investigated to further understand alcohol-enhanced permeation mechanisms. Both thermodynamic and kinetic variables associated with the enhanced permeation of mannitol were ascertained in the presence of high concentrations of short chain alcohols. Permeation of mannitol through human epidermis in the presence of 75% (v/v) alcohol-saline mixtures was determined in symmetric, side-by-side diffusion cells at 32°C. Permeability coefficients increased with increasing alcohol chain length ( iso-propanol > ethanol > methanol ). Uptake of mannitol into the epidermal tissue increased in the presence of the short chain alcohols, but was independent of alcohol chain length. In addition, mannitol solubility decreased in the presence of the short chain alcohols, but again was independent of alcohol chain length. Therefore, increased mannitol permeability with increasing alcohol chain length could not be attributed to thermodynamic variables. Changes in the amount and conformation of stratum corneum lipids and proteins were determined by Fourier transform infrared (FTIR) spectroscopy. Stratum corneum lipid conformation and mobility was not significantly altered in the presence of the short chain alcohols. However, decreased absorbance of the alkyl chain suggested lipid extraction, which increased with increasing alcohol chain length. Stratum corneum protein conformation was altered in the presence of the short chain alcohols. Decreased infrared absorbance of the Amide I band maximum suggested extraction of stratum corneum proteins, which increased with increased alcohol chain length. These results suggest a correlation between enhanced permeation and extraction of lipids as well as proteins from human skin in the presence of 75% (v/v) aqueous alcohol solutions.

Effect of different butanols on the adsorption of sodium dodecylsulfate on alumina

The adsorption of sodium dodecylsulfate onto alumina from aqueous solutions (0.3 M NaCl) was determined in the presence of short-chain alcohols,i.e.,1-, 2-,iso-, andtert-butanol. All adsorption isotherms of the surfactant show the same trend upon the addition of the different short-chain alcohols. The isotherm reaches its saturation level at lower surfactant equilibrium concentrations than without alcohol, and the saturation adsorption density level decreases. The reason for these changes is attributed mostly to the lowering effect of butanols on the critical micelle concentration of sodium dodecylsulfate in the aqueous bulk phase, but also the competitive adsorption of the alcohols is considered.