Effect Of Carbon Chain Length Research Articles

A hierarchical single-pulse shock tube pyrolysis study of C2–C6 1-alkenes

A single-pulse shock tube study of the pyrolysis of 2% C2–C6 1-alkenes is presented at 2 bar in the temperature range 900–1800 K in the current study. Reactant, intermediate and product species are obtained and quantified using gas chromatography-mass spectrometry (GC–MS) analysis. MS is used for species identification and a flame ionization detector is used for quantification. The experiments show the effect of carbon chain length on the production of smaller C1–C3 fragments. A new detailed kinetic mechanism, NUIGMech1.0, is used to simulate the data and the predictions for the major species are satisfactory. The improvement in predictions of the current mechanism, which includes C6 and C7 species, is substantial compared to AramcoMech3.0. Kinetic analyses are conducted with the current mechanism to identify the formation and consumption pathways of the quantified species. The experimental data are expected to contribute to a database for the validation of mechanisms at pyrolytic conditions. Additionally, the mechanism aims to provide a fundamental understanding of the pyrolytic chemistry of olefins.

Lumichrome tautomerism in alcohol-water mixtures: Effect of carbon chain length and mole fraction of alcohols

Alcohol-water mixtures are important solvent systems, widely used in many applications. In this study, the intriguing water induced tautomerism of the fluorescent chromophore, Lumichrome (LC), has been explored to reveal interesting changes in the solvent environments of alcohol-water mixtures of methanol (MeOH), ethanol (EtOH), n-propanol (PrOH) and tert-butanol (t-BuOH), as a function of the carbon chain length/alkyl group size and concentrations of the alcohols. Since LC remains in the alloxazine form in pure aqueous medium, the appearance of emission from the isoalloxazine tautomer in alcohol-water mixtures provides compelling evidence that addition of alcohol disrupts the H-bonded network structure of bulk water to facilitate the availability of isolated water molecules in the solvent medium, which can form the required LC-water precursor complex for conversion of the alloxazine form to isoalloxazine form. Interestingly, two estimated parameters for LC tautomerism, namely, Rlong, which is the relative emission contribution of the isoalloxazine form in the fluorescence decay traces of LC (and hence a measure of the population of isoalloxazine form in the solution), and τlag, which is the lagtime involved in the evolution of the isoalloxazine emission band in the time-resolved area normalized emission spectra of LC (and hence a measure of the ease with which the LC-water precursor complex is formed), show a non-monotonic dependence on the mole fraction of alcohols (χalcohol) in the mixed solvent systems. The unique variation of Rlong and τlag with χalcohol, indicates the occurrence of three composition zones in the alcohol-water mixtures, which we correlate with characteristic transformations in the microscopic structures of the solvent mixtures. Our results reveal that the ability of the alcohols to disrupt the H-bonded network structure of bulk water increases with increasing size of their hydrophobic alkyl groups, following the trend, t-BuOH > PrOH > EtOH > MeOH.

An Insight on Thermophysical Properties of Binary Mixtures of Hydrocarbons with Spectroscopic Evidence; Essential Components of Transformer Oils

The aim of the present investigation is to analyze the effect of carbon chain length in benzene + (hexane/heptane) binary mixtures at different temperatures through density (ρ), ultrasonic velocity (U), viscosity (η) and dielectric (ε) measurements. Derived properties such as molar volume (V), isentropic compressibility (βs), acoustic impedance (Z) and intermolecular free length (Lf) have been calculated for T = 298.15, 308.15 and 318.15K. The excess values of the above mentioned properties of the binary mixtures of benzene + (hexane/heptane) are determined at different temperatures and have been fitted to Redlich – Kister polynomial equation. The dielectric permittivity results demonstrate that deviations from pure components are mostly negative in both the mixtures except for few cases in benzene rich region. Excess Gibb’s free energy of activation of viscous flow (GE) has been calculated using the viscosity measurements at different temperatures. Mixing rules have been adopted to calculate the ultrasonic velocities of the binary mixtures of benzene + (hexane/heptane) at the above said temperatures. FT-IR and NMR analysis have been done to check the accuracy of the results.

Toxicity of perfluorinated compounds to soil microbial activity: Effect of carbon chain length, functional group and soil properties

Perfluorinated compounds (PFCs) have been detected at various concentrations in different environment compartments due to their widespread usage. Nowadays, soil environment has become a prominent sink of PFCs from surface runoff and penetration, but few researches have been conducted in the toxicity of PFCs to soil microorganisms. To address the issue, microcalorimetry was applied to investigate the toxicity of six PFCs with different carbon chain length (4, 8, and 10) and functional group (carboxylic and sulfonic) to microbial activities in three Chinese soils varying widely in soil properties. Adsorption of PFCs by soil matrix was a key factor in controlling the toxicity of PFCs to soil microorganisms. The differences of carbon chain length and functional groups of PFCs have different impacts on soil microbial activity while affecting adsorption progress. Particularly, the sulfonic PFCs expressed higher toxicity than the carboxylic. It is also identified that the longer the chain length, the greater the toxicity of PFCs. Soil pH was another relevant factor of soil adsorption, and with the increase of pH, adsorption capability increased. Soil available P, N and K were essential nutrients in soil, and suggested to improve microbial activity under PFCs stress.

Conversion of C2–4 Carboxylic Acids to Hydrocarbons on HZSM-5: Effect of Carbon Chain Length

The conversion of C2–4 carboxylic (acetic, propionic, and n-butyric) acids on HZSM-5 was studied at 350 °C. The reaction proceeds through ketonization (to acetone, 3-pentanone, and 4-heptanone, respectively), aldol condensation, and tertiary reactions to aromatics-rich hydrocarbons. The product distribution is influenced by the carbon chain length of carboxylic acids due to the shape selectivity of ZSM-5. The turnover frequency (TOF) of ketonization of carboxylic acids decreases while the TOF of aldol condensation of corresponding ketones increases with increasing carbon chain length. Langmuir–Hinshelwood mechanism analysis shows that the true activation enthalpy of both ketonization and aldol condensation increases with increasing carbon chain length, due to the increased steric hindrance for the formation of a C–C bond. However, the true Gibbs free activation energy increases for ketonization but decreases for aldol condensation with increasing chain length, due to a greater contribution of activation e...

Surprising Effect of Carbon Chain Length on Inducing Ability of Additives: Elusive Form-II of γ-Aminobutyric Acid (GABA) Induced by Sodium Carboxylate Additives

Herein, we developed the strategy of additive-induced polymorph, realizing the selective crystallization of elusive Form-II of γ-aminobutyric acid, a potent bioactive compound. A series of sodium carboxylate additives with different carbon chain lengths (C2–C8) were identified to induce the crystallization of Form-II. It was found that additive molecules will inhibit the growth of the centrosymmetric Form-I at two opposite ends, thereby precluding it, but they will inhibit the growth of the polar Form-II at only one end so that it survives. Notably, these sodium carboxylate additives exhibited distinct inducing ability for Form-II; that is, the effective critical addition amount required to induce Form-II increases with the increase of carbon chain length. However, the sodium formate is an exception and it cannot induce the Form-II. The difference of the inducing ability of additives was rationalized based on the competition of attachment and detachment behavior of additives on the growth end of Form-I. W...

Predicting sooting tendencies of oxygenated hydrocarbon fuels with machine learning algorithms

The use of oxygenated components is an effective way to suppress soot formation and reduce particulate matter emission in diesel engines. Based on the group additivity method, we proposed a new statistical model with kernel ridge regression (KRR) to predict the sooting tendencies of oxygenated components and interpret the experimental results of fuel sooting tendency. Through a training process, the relationship between fuel molecular structure and sooting tendency was built. In the testing process, the predicted values of the yield sooting index were in good agreement with the measured values, indicating that the KRR model had good predictive performance. The KRR method can be used to compare the sooting tendencies of various components that are important in traditional or new fuels. For example, based on the predicted results of typical five-carbon oxygenated compounds, the inhibiting effects of oxygen functional groups on sooting tendency are in the following order: esters > ketones ≈ aldehydes > ethers > alcohols. In addition, the proposed method provides statistical evidence for the effects of structural features on sooting tendencies. The predictive results for typical ethers indicate that although sooting tendencies increase as carbon chains become more branched, they are not very sensitive to the specific arrangement of the branches compared with the effect of carbon chain length. Moreover, the KRR method is useful for studying non-nearest-neighbor interactions, including functional group interactions. By predicting the sooting tendencies of typical esters, the coupling of ester moiety and CC double bonds shows an overall enhancing effect on sooting tendency, which indicates that CC double bonds play a dominant role in soot formation. This method provides an alternative way to obtain the sooting tendencies of fuel compounds and verifies the selection of low-sooting fuels from a wide range of feedstocks.

VLE measurements and modelling for the binary systems of (CF4 + C6F14) and (CF4+ C8F18)

Isothermal phase equilibrium data were measured for the binary systems of tetrafluoromethane with either perfluorohexane or perfluorooctane to investigate the effect of carbon chain length of the solvent with regards to the solubility of tetrafluoromethane. Both the “static-analytic” and the “static-synthetic” methods were utilized to measure the high-pressure phase equilibrium data. Isothermal measurements were performed within the temperature range of (283.15–303.15) K and at pressures up to 11 MPa. Vapour pressure data for perfluorohexane and perfluorooctane were measured within the temperature range of (283.15–323.15) K. Additionally, isothermal vapour-liquid equilibrium data were measured for the binary system of carbon dioxide + n-hexane at 313.15 K; the data were utilized to validate the experimental method. The experimental data were modeled using the Peng-Robinson equation of state with the Wong-Sandler mixing rule and Non-Random Two-Liquid excess Gibbs energy model. The model provides a satisfactory representation of the experimental data within the measured temperature range.

Pressure Stabilization of Criegee Intermediates Formed from Symmetric trans-Alkene Ozonolysis.

We explore the pressure dependence of a stabilized Criegee Intermediate (sCI) formation from a sequence of trans-alkene ozonolysis reactions. To study the effect of carbon chain length on the stabilization, we select five symmetric trans-alkenes ranging from trans-2-butene (C4) through trans-7-tetradecene (C14). We measure the pressure falloff curves for each alkene from 50 to 900 Torr in a flow reactor using conversion of SO2 to H2SO4 with and without an OH scavenger, and subsequent detection of H2SO4 with a nitrate chemical ionization mass spectrometer to constrain sCI yields. As the length of the carbon chain increases, we observe a systematic increase in Criegee Intermediate stabilization at a given pressure, along with a systematic decrease in the low-pressure limit. Our results also suggest that for these symmetrical systems the anticonformer of the Criegee Intermediate stabilizes before (at lower pressure than) the syn conformer.

Effects of carbon chain length of imidazolium-based ionic liquid in the interactions between heavy crude oil and sand particles for enhanced oil recovery

Increasing demand and dwindling supply of crude oil have spurred efforts towards enhancing heavy oil recovery. Recently, applications of ionic liquids (ILs) for heavy oil recovery and catalytic upgrading have been intensively studied due to their novelty as green surfactants. This paper presents the effects of different carbon chain lengths (n = 0, 2, 4, 6, 8, 10, 12) and concentrations from 1000 to 8000 ppm of imidazolium-based ILs on the oil-sand detachment efficiency at room temperature. Overall, the longest carbon chain length (n = 12), 1-dodecyl-3-methylimidazolium chloride ([DODmim][Cl]), showed highest oil-sand detachment efficiency of approximately 80% at 4000 ppm and beyond, indicating that a CMC point has been achieved. In contrary, the IL without carbon chain length (n = 0), 1-methylimidazolium chloride ([Mmim][Cl]), showed lowest oil-sand separation of a mere 5.7% at all concentrations. Interfacial tension (IFT) and zeta potential measurements further verified the above oil-sand detachment efficiencies, whereby the high oil-sand detachment efficiencies correlated to low IFT of approximately 9.78 mN/m for [DODmim][Cl] at 8000 ppm and high net zeta potential measurements of positively charged oil and sand particles. It is interesting to note that while the zeta potential measurements were all positive for oil particles in IL, the zeta potential measurements of sand particles in IL turned to negative for low concentrations of [Omim][Cl] and shorter carbon chain lengths (n ≤ 6), thus resulting in a mild attraction between the oil and sand particles. Further analysis using the Derjaguin-Landau, Verwey Overbeek (DLVO) theory which showed the inter-particle forces further validated the former oil-sand detachment efficiencies whereby repulsive forces between oil and sand particles occurred only for longer carbon chain lengths of [DODmim][Cl] and [Dmim][Cl].

Synthesis, characterization, spectroscopy and biological activity of 4-((3-formyl-4-hydroxyphenyl)azo)-1-alkylpyridinium salts

The reaction of 2-hydroxy-5-(pyridine-4-yldiazenyl)benzaldehyde with n-alkyl bromides generated five novel azo pyridinium salts in good to excellent yields. The $$^{1}\hbox {H}$$ and $$^{13}\hbox {C}$$ NMR and UV-Vis absorption spectra indicated several tautomers for the new compounds. The NMR, UV-Vis absorption spectra and quantum chemical calculations show that the azo pyridinium salts have a new resonant structure compared to the corresponding azo precursor. Antibacterial activity was studied by disc diffusion and MIC methods. Diphenylpicrylhydrazyl (DPPH) assay was used to determine the antioxidant properties. The effects of carbon chain length on antimicrobial activity were also investigated. The results showed that existence of alkyl groups is crucial for the antibacterial properties. The new compound with decyl group displayed the best antibacterial activity. SYNOPSIS Five novel azo pyridinium salts were synthesized in high yield. Resonant structures in azo pyridinuim were studied by $$^{1}\hbox {H}$$ NMR and UV-Vis spectra. Antibacterial and antioxidant properties were also investigated.

Effects of Carbon Chain Length on the Perfluoroalkyl Acids-Induced Oxidative Stress of Erythrocytes in Vitro

Perfluoroalkyl acids (PFAAs) have been found extensively in wildlife and human bodies by sources of drinking water and food. In this study, we investigated the effects of three PFAAs, perfluoropentanoic acid (PFPA), perfluorooctanoic acid (PFOA), and perfluorodecanoic acid (PFDA), on the antioxidative defense system and lipid peroxidation in erythrocytes separately. The results demonstrated that they could lead to significant decline trends in the glutathione (GSH) levels together with increases of malondialdehyde (MDA) content, suggesting that three PFAAs induced oxidative stress to erythrocytes. Also PFDA with a longer carbon chain length posed more of a threat than other two PFAAs. Furthermore, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) were also altered in the presence of PFAAs upon erythrocytes. The changes of oxidative stress markers and the concomitant alterations of antioxidant enzymes suggest the role of oxidative stress in PFAA-induced damage upon erythrocytes.

Investigation of n-dodecane pyrolysis at various pressures and the development of a comprehensive combustion model

n-Dodecane combustion was investigated experimentally and numerically in present study. Pyrolysis experiments of n-dodecane at pressures of 0.0066, 0.039, 0.197 and 1 atm, temperatures from 750 to 1430 K were studied in a flow reactor. Mole fractions of n-dodecane, argon and pyrolysis products (including active radicals) were evaluated. A kinetic model of n-dodecane was developed by validating both present and literature reported experiments. The rate of production analysis reveals H-abstraction and CC bond fission reactions are main consumption pathways of n-dodecane. The β-CC scission reactions of alkyls contribute to the formation of alkenes, which are mainly consumed via the allylic CC fission reactions. As a soot precursor, benzene is largely produced from the recombination of C3 species. Moreover, effects of carbon chain length on flow reactor pyrolysis were investigated for n-decane, n-dodecane and n-tetradecane. The decay of n-tetradecane is the fastest, followed by n-dodecane and n-decane, indicating that the pyrolysis reactivity of n-alkanes increases as the carbon chain length increases from C10 to C14n-alkanes. Ignition delay times and laminar burning velocities (LBVs) of n-alkanes under similar conditions were also compared, the result shows that effects of the carbon chain length on ignition delay times and LBVs are slight.

The effect of carbon chain length of starting materials on the formation of carbon dots and their optical properties

Carbon dots (CDs) have attracted increasing attention due to their high performances and potential applications in wide range of areas. However, their emission mechanism is not clear so far. In order to reveal more factors contributing to the emission of CDs, the effect of carbon chain length of starting materials on the formation of CDs and their optical properties was experimentally investigated in this work. In order to focus on the effect of carbon chain length, the starting materials with C, O, N in fully identical forms and only carbon chain lengths being different were selected for synthesizing CDs, including citric acid (CA) and adipic acid (AA) as carbon sources, and diamines with different carbon chain lengths (H2N(CH2)nNH2, n = 2, 4, 6) as nitrogen sources, as well as ethylenediamine (EDA) as nitrogen source and diacids with different carbon chain lengths (HOOC(CH2)nCOOH, n = 0, 2, 4, 6) as carbon sources. Therefore, the effect of carbon chain length of starting materials on the formation and optical properties of CDs can be systematically investigated by characterizing and comparing the structures and optical properties of as-prepared nine types of CDs. Moreover, the density of –NH2 on the surface of the CDs was quantitatively detected by a spectrophotometry so as to elucidate the relationship between the –NH2 related surface state and the optical properties.

Effects of structure of fatty acid collectors on the adsorption of fluorapatite (0 0 1) surface: A first-principles calculations

Effects of carbon chain length, carbon chain isomerism, CC double bonds number on fatty acid adsorption on FAP (0 0 1) surface have been investigated based on DFT. The results revealed that fatty acid collector can form stable adsorption configuration at Ca1 (surf) site. Chemical adsorption was formed between O (mole) of fatty acid collector and the Ca1 (surf) of fluorapatite (0 0 1) surface; hydrogen bond adsorption was formed between the H (mole) of fatty acid and the O (surf) of-[PO4]- of FAP (0 0 1) surface. Fatty acid collectors and FAP (0 0 1) surface are bonding by means of the hybridization of O (mole) 2p and Ca (surf) 4d orbitals, H (mole) 1s and O (surf) 2p orbital. The analysis of adsorption energy, DOS, electron density, Mulliken charge population and Mulliken bond population revealed that with the carbon chain growing within certain limits, the absolute value of the adsorption energy and the overlapping area between the DOS curve of O (mole) and Ca (surf) was greater, while that of H (mole) 1s and O (surf) 2p basically remained unchanged. As CC double bonds of fatty acids increased within certain limits, the adsorption energy and the overlapping area between the state density curve of O (mole) and Ca (surf), H (mole) and O (surf) basically remained unchanged. The substituent groups of fatty acid changed, the absolute value of the adsorption energy and the overlapping area between the state density curve had a major change. The influence of fatty acids adsorption on FAP (0 0 1) surface depends mainly on the interaction between O (mole) and Ca (surf).

Increasing Dietary Medium-Chain Fatty Acid Ratio Mitigates High-fat Diet-Induced Non-Alcoholic Steatohepatitis by Regulating Autophagy

Previous studies have demonstrated that saturated fatty acids (SFAs) are more lipotoxic than unsaturated fatty acids (UFAs) in inhibiting hepatic autophagy and promoting non-alcoholic steatohepatitis (NASH). However, there have been few studies have investigated the effects of carbon chain length on SFA-induced autophagy impairment and lipotoxicity. To investigate whether SFAs with shorter carbon chain lengths have differential effects on hepatic autophagy and NASH development, we partially replaced lard with coconut oil to elevate the ratio of medium-chain fatty acids (MCFAs) to long-chain fatty acids (LCFAs) in a mouse high-fat diet (HFD) and fed mice for 16 weeks. In addition, we treated HepG2 cells with different combinations of fatty acids to study the mechanisms of MCFAs-mediated hepatic protections. Our results showed that increasing dietary MCFA/LCFA ratio mitigated HFD-induced Type 2 diabetes and NASH in mice. Importantly, we demonstrated that increased MCFA ratio exerted its protective effects by restoring Rubicon-suppressed autophagy. Our study suggests that the relative amount of LCFAs and MCFAs in the diet, in addition to the amount of SFAs, can significantly contribute to autophagy impairment and hepatic lipotoxicity. Collectively, we propose that increasing dietary MCFAs could be an alternative therapeutic and prevention strategy for Type 2 diabetes and NASH.

Effect of carbon chain length of dicarboxylic acids as cross-linking agents on morphology, encapsulation, and release features of protein-loaded chitosan microparticles

Chitosan microparticles were obtained by emulsion cross-linking technique. Impact of the carbon chain length of dicarboxylic acids (malonic, succinic, glutaric, adipic, pimelic, suberic, and azelaic) as cross-linking agents on morphology, encapsulation, and release of bovine serum albumin (BSA) was studied. Role of the polyglycerol polyricinoleate as surfactant to stabilize the pre-emulsions and its influence on the structure of the particles obtained was considered. The increase in the carbon chain length of dicarboxylic acids gives rise of the mass-average diameter of the microparticles. The greatest encapsulation ability of the cross-linked samples is observed for pimelic and suberic acids. The BSA encapsulation for azelaic acid decreases with the increase in the carbon chain length. The ratios of the initial and total cumulative releases of BSA for 24 h increase with the increase of the number of carbon atoms in dicarboxylic acid from 3 to 7. Beginning with the sample of cross-linked suberic acid, the dramatic decrease in the percentage of the initial release of BSA is occurred. The same dependence is observed for the swelling ratio due to the increase in the hydrophobic interactions within chitosan matrix and the growth of the thickness of dicarboxylic acid-polyelectrolyte layers on the surface of the microparticles. The carbon chain length of the above dicarboxylic acids was concluded to be available mode to control the properties of chitosan microparticles as vehicles for drug delivery and drug release.

A Novel Alkyl Sulphobetaine Gemini Surfactant Based on S‐triazine: Synthesis and Properties

AbstractA series of alkyl sulphobetaine Gemini surfactants Cn‐GSBS (n = 8, 10, 12, 14, 16) was synthesized, using aliphatic amine, cyanuric chloride, ethylenediamine, N,N′‐dimethyl‐1,3‐propyldiamine and sodium 2‐chloroethane sulfonate as main raw materials. The chemical structures were confirmed by FT‐IR, 1H NMR and elemental analysis. The Krafft points differ markedly with different carbon chain length, for C8‐GSBS, C10‐GSBS and C12‐GSBS are considered to be below 0 °C and C14‐GSBS, C16‐GSBS are higher than 0 °C but lower than room temperature. Surface‐active properties were studied by surface tension and electrical conductivity. Critical micelle concentrations were much lower than dodecyl sulphobetaine (BS‐12) and decreased with increasing length of the carbon chain from 8 to 16, and can reach a minimum as low as 5 × 10−5 mol L−1 for C16‐GSBS. Effects of carbon chain length and concentration of Cn‐GSBS on crude oil emulsion stability were also investigated and discussed.

Effect of Carbon Chain Length of Alcohols on the Syntheses of Cinnamate Esters by Immobilized Lipase from Bacillus aerius

Background: Celite- immobilized lipase was used to catalyze the esterification reaction between different alcohol of carbon chain in increasing order viz. methanol, ethanol, propanol and butanol to form cinnamate esters in DMSO (solvent) at different temperatures for different time periods in a chemical reactor. Keywords: Bacillus aerius, cinnamate esters, FTIR spectra, lipase immobilization, NMR spectra.

Effects of Carbon Chain Length of Solvents on the Charateristics of CdSe Quantum Dots

Effects of Carbon Chain Length of Solvents on the Charateristics of CdSe Quantum Dots