Increase In Chain Length Of Alcohol Research Articles

Control over the photophysical properties of nanoparticles of regioregular poly(3-octylthiophene) using various poor solvents

In this study, we demonstrate an ability to control the photophysical properties of nanoparticles of regioregular poly(3-octylthiophene) (rr-P3OT) by utilizing solvent–nonsolvent system. The strength of local polymer–solvent interactions is controlled by using hexane or hexanol as a poor solvent. We have found that the assembling of rr-P3OT chains in mixtures of toluene and these poor solvents results in the formation of nanoparticles with average diameter of about 35nm. Interestingly, the use of hexane or hexanol as a poor solvent causes drastic variation of photophysical properties of the resultant nanoparticles. Their absorption spectra show quite different patterns. In addition, the photoluminescent (PL) peaks are detected at 565nm and 645nm in the systems of toluene/hexane and toluene/hexanol, respectively. Photoemission quantum efficiency of the nanoparticles also depends significantly on type of the poor solvents. We further demonstrate that the photophysical properties can be systematically controlled by using a series of linear alcohols as poor solvents. The increase of alcohol chain length causes the decrease of its polarity, which in turn improves the polymer–solvent interactions. In the system of toluene/decanol, PL spectrum of the nanoparticles covers relatively broad energy region, ranging from about 540 to 770nm. Our study provides a simple method for preparation of rr-P3OT nanoparticles with controllable photophysical properties.

Effect of alcohol chain length on the enzymatic resolution of racemic mandelic acid and kinetic study

Asymmetric esterification of racemic mandelic acid (MA) was conducted in 1,2-dichloroethane using lipase Novozym 435 as catalyst. Different alcohols were screened for esterification to achieve high conversion and enantioselectivity. The results show that ethanol is the best alcohol substrate among tested alcohols, and long-chain alcohols show lower enantioselectivities. The effect of substrate concentrations on esterification with ethanol was studied, and the result indicates an alcohol inhibition. To examine the mechanism of the alcohol chain length effect, the ping-pong bi-bi mechanism with competitive alcohol inhibition was applied to build a model. By comparing the kinetic parameters of methanol, ethanol, butanol, heptanol, and octanol, it was found that both the Michaelis constant and the inhibition constant of alcohol increase with the increase in alcohol chain length, indicating that the balance between nucleophilicity and the inhibition effect is the possible reason for the highest conversion and enantioselectivity as shown by ethanol.

Investigation on the Structure of Water/AOT/IPM/Alcohols Reverse Micelles by Conductivity, Dynamic Light Scattering, and Small Angle X-ray Scattering

We have systematically investigated the effect of alcohols (ethanol, propanol, butanol, and pentanol) on the structure of the water/AOT/IPM system using conductivity, dynamic light scattering (DLS), and small-angle X-ray scattering (SAXS) techniques. The results show that no percolation phenomenon is observed in the water/AOT/IPM system, whereas the addition of ethanol (propanol and butanol) induces apparently percolation. The threshold water content (W(p)) depends closely on the alcohol type and concentration. The effect of alcohols on the conductance behavior is discussed from the physical properties of alcohols, the interfacial flexibility, and the attractive interactions between droplets. The hydrodynamic diameter of droplets (d(H)) obtained from DLS increases markedly with the increase in water content (W(0)); however, it decreases gradually with increasing alcohol chain length and concentration. SAXS measurements display distinctly the shoulder, the low hump peaks, and the heavy tail phenomenon in the pair distance distribution function p(r) profile, which rely strongly on the alcohol species and its concentration. The gyration radius (R(g)) increases with increasing W(0), and decreases with the increase of alcohol chain length and concentration. Schematic diagram of the conductance mechanism of water/AOT/IPM/alcohol systems is primarily depicted. Three different phases of the discrete droplets, the oligomers, and the isolated ellipsoidal droplets existed in the different W(0) ranges correspond to three different stages in the conductivity-W(0) curve. Coupling the structure characteristics of reverse micelles obtained from DLS and SAXS techniques with conductivity could be greatly helpful to deeply understand the percolation mechanism of water/AOT/IPM/alcohols systems.

Kinetics of catalytic esterification of propionic acid with different alcohols over Amberlyst 15

AbstractThe kinetics of the esterification reaction between propionic acid and methanol, ethanol, and 1‐butanol over the ion exchange resin, Amberlyst 15, was investigated. Experiments were conducted using a fixed‐bed plug flow reactor over the temperature range of 298–328 K. Acid to alcohol molar ratios of 3:1, 1:1, and 1:3 were employed. For each esterification system, the equilibrium conversion of propionic acid was found to increase with increasing reaction temperature. Several kinetic models were tested to correlate the collected data under kinetically controlled conditions; the pseudo‐homogeneous (P‐H), Eley–Rideal (E–R), Langmuir–Hinshelwood (L–H), and Pöpken (P‐P) models. In all cases, the activity coefficients were estimated using the UNIFAC model to account for the nonideal thermodynamic behavior of the reactants and products. The P‐P model was found to best represent the kinetic data of the investigated esterification systems with a total average error of less than 3%. The increase of alcohol chain length had a negative impact on the conversion of propionic acid due to steric hindrance. The activation energy of the esterification reaction is influenced by the chain length of the alcohol used. The adsorption equilibrium constants estimated by the P‐P model and the solubility parameters reported by AICHE DIPPER® followed the same trend; ester < acid < alcohol < water. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 432–448, 2009

Probing the Nucleation Mechanism for the Binary n-Nonane/1-Alcohol Series with Atomistic Simulations

The AVUS-HR approach, which combines histogram reweighting with aggregation-volume-bias Monte Carlo nucleation simulations using self-adaptive umbrella sampling, was extended to multicomponent nucleation systems. It was applied to investigate the homogeneous vapor-liquid nucleation for the binary n-nonane/1-alcohol series, including the n-nonane/methanol, n-nonane/ethanol, n-nonane/1-propanol, n-nonane/1-butanol, n-nonane/1-hexanol, and n-nonane/1-decanol systems. The simple transferable potentials for phase equilibria-united atom force field was used in this investigation. It was found that the nucleation free energy (NFE) contour plots obtained for these binary n-nonane/1-alcohol nucleation systems exhibit rather interesting mechanistic features, some of which are distinct from other binary systems previously studied (such as water/ethanol and water/n-nonane). In addition, the NFE profiles show a subtle evolution with the increase in alcohol chain length, from a somewhat two-pathway type of shape as observed for the n-nonane/methanol system to a more normal single-pathway one for systems involving longer alcohols (1-hexanol and 1-decanol). In contrast, the NFE maps obtained for the other three binary systems involving those medium-length alcohols display the most striking feature with the saddle point stretched almost all the way from the n-nonane-enriched to the alcohol-enriched domain, implying that multiple pathways coexist on the nucleation map. These free energy profiles were shown to be consistent with the non-ideal nucleation behavior observed experimentally for this binary series, namely, a rather reluctant conucleation of the alcohols with n-nonane. In particular, this non-ideal behavior becomes more severe with a decrease in the alcohol chain length. Also, analysis of the compositions of the critical nuclei indicates a reluctant mixing behavior between these two species, i.e., depletion of the alcohol at low alcohol activity or depletion of n-nonane at low n-nonane activity, in agreement with the experimental interpretations. Furthermore, a microscopic inhomogeneity is present inside these critical nuclei, that is, alcohols aggregate via hydrogen bonds forming alcohol-enriched domains.

Phase diagram of α‐sulfonate methyl esters derived from palm stearin/alcohol/water systems

AbstractPhase diagrams of α‐sulfonate methyl ester derived from palm stearin (α‐SMEPS)/alcohol/water systems were mapped at 30±0.1°C. Two main regions—an isotropic and a lamellar liquid crystalline—were the focal points in this system. An increase in alcohol chain length decreased the isotropic region and increased the lamellar liquid crystal region. In the isotropic region, self‐assembly of α‐SMEPS at different alcohol chain lengths was determined by using conductivity and viscosity measurements. The phase boundaries of micelle to bicontinuous structure and bicontinuous structure to inverse micelle transitions in the isotropic regions are proposed from these analytical methods. The increase in alcohol chain length shifted the micelle ⇆ bicontinuous structure to the water‐rich corner, and the bicontinuous structure ⇆ inverse micelle transition moved toward the alcohol‐rich corner.

異なるアルコール鎖長をもつドコサヘキサエン酸エステルの自動酸化（原標題は英語）

Four esters of docosahexaenoic acid, methyl (DHA-ME), ethyl (DHA-EE), propyl (DHA-PE) and isopropyl docosahexaenoate (DHA-IE), were synthesized and autoxidized at 25°C to determine how the ester structure provides stability to highly unsaturated fatty acid (HUFA) against oxidation. Stability was assessed based on oxygen absorption during autoxidation. Monohydroperoxide (MHPO) isomers were examined by high-performance liquid chromatography (HPLC). DHA-ME was found to undergo oxidation most rapidly, whereas DHA-IE was most stable toward this process. Induction period of DHA esters was longer with greater alcohol chain length. HPLC demonstrated the presence of ten MHPO positional isomers (4-,7-,8-,10-,11-,13-,14-,16-,17-and 20-MHPO) during autoxidation of the DHA esters. 20-MHPO was the main constituent of any one of these isomers, constituting 20% of total MHPO regardless of the DHA esters. Peroxide had virtually no effect on MHPO isomer compostion. 4-MHPO was produced in the least amount from autoxidized DHA-ME (8%), though more so from autoxidized DHA-IE (17%). More 4-MHPO was obtained from total MHPO with increase in alcohol chain length. MHPO produced from during autoxidation of DHA-EE, DHA-PE and DHA-IE was stable, during its incubation at 25°C, whereas only 4-MHPO of DHA-ME was unstable. Ester structure is thus shown to provide stability toward oxidation and products obtained from the oxidation of DHA.

Sucrose ester microemulsions as microreactors for model Maillard reaction

Thermal reactions of cysteine/furfural mixture were studied as a model system to gain more insight into the influence of structured fluids such as water-in-oil nonionic microemulsions on the generation of aroma compounds. The microemulsion systems were composed of: sucrose ester/water/dodecane+alcohol(1/1), where the sucrose esters are sucrose stearate (S1570) and sucrose laurate (L1695), and the alcohols are medium-chain alcohols (C 2OH to C 6OH). Formation of predominately 2-furfurylthiol (FFT) is obtained in the aqueous cysteine/furfural system. The formation of FFT was enhanced under similar reaction conditions in water-in-oil microemulsions and led to the formation of two new sulfur compounds that were identified as 2-(2-furyl)-thiazolidine and tentatively N-(2-mercaptovinyl)-2-(2-furanyl)-thiazolidine. The reaction rates (furfural conversion or consumption) decrease with the decrease in the water content and the increase in alcohol chain length (C 2 to C 6 were used as cosurfactant) and with the increase of pH from 4 to 8 in the system containing butanol as the alcohol. The rates of reaction increase also with the increase of temperature in the range of temperatures studied from 30 to 60 °C. The kinetic constants ( k) and energy of activation ( E a) were calculated. Microemulsions of W/O are excellent reaction media for the Maillard reaction providing a high selectivity, high conversion rates and specificity.