Hydrocarbon Chain Length Research Articles

Effect of akyl chain length, flow, and temperature on the corrosion inhibition of carbon steel in a simulated acidizing environment by an imidazoline-based inhibitor

An imidazoline, 2-heptadecyl-1-[2-(octadecanoylamino)ethyl]-2- imidazoline (QSI) with -C17H35 as the tail chain length was synthesized, characterized, and studied as corrosion inhibitor for low carbon steel in 15% HCl solution under static and hydrodynamic conditions. Influence of addition of KI, temperature, and chain length of pendant hydrocarbon on inhibition efficiency (η) was also examined. It is found that, QSI exhibits a mixed type behavior but fairly inhibited the corrosion of low carbon steel in the studied medium. The maximum concentration studied (400 mg/L) afforded η of <50%. Addition of KI to QSI synergistically enhanced the corrosion inhibition performance of QSI, upgrading the η to approximately 90%. Increase in the system temperature increases the η of both QSI and QSI + KI. From the variation of η with temperature and the calculated corrosion kinetic parameters, chemical adsorption is proposed as the adsorption mechanism of the additives. QSI performs better under hydrodynamic condition than static condition. However, the corrosion resistance of the metal decreases at rotation speed higher than 1000 rpm. Inhibition efficiency of imidazoline decreases as the length of the hydrocarbon pendant chain increases. Imidazoline compounds with -C13H27 and -C15H31 as the length of the pendant group hydrocarbon perform better than QSI with -C17H35.

Viscoelastic surfactant fracturing fluids for use in coal seams: Effects of surfactant composition and formulation

Recently, viscoelastic surfactant (VES) fracturing fluids have attracted wide attention because they are highly viscoelastic and environmentally benign. To optimize fracturing fluid formulations for coal reservoir conditions, 135 groups of VES fracturing fluids were prepared. The influence of the cationic surfactant’s hydrocarbon chain lengths on water loss, wettability, viscosity, and temperature resistance were analyzed. To further improve the surfactant’s aggregation capabilities, zwitterionic surfactants were added to fracturing fluids prepared with stearyl trimethyl ammonium chloride (STAC). We found that STAC can reduce water loss more effectively during fracturing than the cationic surfactant hexadecyl trimethyl ammonium chloride (CTAC). Appropriate amounts of cocoamidopropyl betaine (CAB) increased the viscosity and temperature resistance of the fracturing fluid. It is important to note that as the concentration of sodium salicylate (NaSal) increases, the maximum viscosity of VES fracturing fluid with CAB added is twice that of a fracturing fluid without CAB.

The first observation of electrochemistry of graphene/cysteine/copper composite

A systematic characterization of electron transfer reaction involving copper amino acid complexes is an interesting task in connection with a biological activity of copper. We immobilized copper on a self-assembled monolayer of different types of cysteines grown on graphene electrode. Copper-amino acid complexes were characterized by electrochemical methods such as cyclic voltammetry. Influence of pH of electrolyte, hydrocarbon chain length of cysteine and concentration of copper chloride solution used for immobilization of copper on amino acid self-assembled monolayer/graphene composite, on electron transfer process were tested. Strong signal of copper (II) reduction was obtained in the phosphate buffer solution at pH 6.2 and no significant change was observed after change the hydrocarbon chain length on electrochemistry of graphene/cysteine/copper composite.Apart from fundamental interest, Cu2+ containing device could be interesting to study as effective copper ion sensors/catalysts on their own. One more aspect of this paper is exploitation of graphene as a supporting substrate for self-assembled monolayers.

Imidazolium-based ionic liquids cause mammalian cell death due to modulated structures and dynamics of cellular membrane

Here, we report the toxic effects of various imidazolium-based ionic liquids (ILs) with varying hydrocarbon chain lengths, on different human cell lines. Multiple biological assays have shown that the ILs with long hydrocarbon chains have stronger adverse effect especially on human liver cancer cells (Huh-7.5 cells). Further, our study has confirmed that the ILs induce necrosis dependent cell death and that it is related to cell membrane damage. To understand the molecular mechanism of such an effect, the cellular membranes were mimicked as lipid monolayers formed at the air-water interface and then as lipid bilayer vesicles. The pressure area-isotherms measured from the monolayer have shown that the interaction of ILs with the lipid layer is energetically favourable. The addition of these ILs reduces the in-plane elasticity of the self-assembled molecular layer. Quasielastic neutron scattering data clearly indicate that ILs in liver lipid vesicles significantly affects the dynamics of the lipid, in particular, the lateral motion of the lipids. It has been concluded that the mammalian cell death induced by these ILs is due to the modulated structure and altered physical properties of the cellular membrane.

Hydrocarbon Chain-Length Dependence of Solvation Dynamics in Alcohol-Based Deep Eutectic Solvents: A Two-Dimensional Infrared Spectroscopic Investigation.

Deep eutectic solvents (DESs) have gained popularity in recent years as an environmentally benign, inexpensive alternative to organic solvents for diverse applications in chemistry and biology. Among them, alcohol-based DESs serve as useful media in various applications due to their significantly low viscosity as compared to other DESs. Despite their importance as media, little is known how their solvation dynamics change as a function of the hydrocarbon chain length of the alcohol constituent. In order to obtain insights into the chain-length dependence of the solvation dynamics, we have performed two-dimensional infrared spectroscopy on three alcohol-based DESs by systematically varying the hydrocarbon chain length. The results reveal that the solvent dynamics slows down monotonically with an increase in the chain length. This increase in the dynamic timescales also shows a strong correlation with the concomitant increase in the viscosity of DESs. In addition, we have performed molecular dynamics simulations to compare with the experimental results, thereby testing the capacity of simulations to determine the amplitudes and timescales of the structural fluctuations on fast timescales under thermal equilibrium conditions.

CO2-responsive surfactants with tunable switching pH

HypothesisOne of the major challenges in applying CO2-responsive surfactants concerns their tunable switchability and robustness under operating conditions. We hypothesize that combining monoethanolamine (MEA) with long-chain fatty acids (LCFAs) of variable chain lengths through electrostatic attraction could develop a series of CO2-responsive surfactants with tunable switching pH. ExperimentsThe tunability of switching pH for this group of surfactants was demonstrated by in situ probing of the CO2-responsive characteristics at the oil/water interface using dynamic interfacial tension (IFT) measurements. Two protocols were applied to distinguish interfacial response and solution response. The key importance of interfacial response was demonstrated by two essential applications of CO2-responsive surfactants: demulsification of stable emulsions, and alternation of the interfacial properties of ultra-heavy crude oil-water interfaces. FindingsThe switching pH of the CO2-responsive surfactants was controlled by the hydrocarbon chain length of LCFAs. More importantly, their switching behaviour was found to be different at the interface and in the bulk solution, which is attributed to the enhanced molecular interactions at the interface. Since most applications require surfactants to be switched at the interface, it is thereby most appropriate to determine the switching pH through their interfacial responses.

Temperature dependent volumetric and acoustic properties of some amino acids in aqueous solutions of an antidepression drug

The interactions of amino acids (histidine, valine and glycine) with drug amitriptyline as a subordinate of temperature have been perused by combination of volumetric and acoustic methods. Densities and speeds of sound of histidine, valine and glycine in aqueous solutions of amitriptyline have been measured at T = (305.15, 310.15 and 315.15) K. Apparent molar volume Vφ, apparent molar isentropic compression kφ, s, of amino acids (solute) in binary aqueous solutions of (0.0006, 0.001, 0.002 and 0.004) mol. kg−1 amitriptyline (solvent) have been designated at reported temperatures. The mentioned parameters are used to construct the solute–solvent interactions in ternary systems. The dependency of these parameters on concentration, temperature and hydrocarbon chain length of the amino acids clearly suggest the roles of amino acids in solute-solvent interactions.

Synthesis and Physicochemical Properties of Novel Phenyl-Containing Sulfobetaine Surfactants

A novel series of sulfobetaine surfactants, 3-((4-(alkoxy)-3,5-dimethylbenzyl) dimethylammonio)-2-hydroxy-propane-1-sulfonate (CnOBSb, n = 12, 14, and 16), were synthesized for the first time. The chemical structures of products were characterized by high-resolution mass spectra, 1H NMR, and 13C NMR spectrometry. The physicochemical properties of CnOBSb were studied by thermogravimetric analysis, equilibrium surface tension measurement, steady-state fluorescence, dynamic light scattering (DLS), and cryogenic transmission electron microscopy (cryo-TEM). The results demonstrated that surface tension values of CnOBSb are in the range of 28.32–30.14 mN/m at a fairly low critical micelle concentration (cmc). The adsorption and micellization properties of CnOBSb were dependent on the hydrocarbon chain length and presence of phenyl group. The results of DLS and cryo-TEM measurements revealed that CnOBSb molecules spontaneously formed vesicles in aqueous solution above the cmc. Furthermore, the application proper...

Vibrational eigenmodes of phospholipid layers in low‐wavenumber Raman spectrum of multilamellar vesicles

AbstractLow‐wavenumber Raman spectra of multilamellar vesicles are studied for phospholipids differing in the unsaturation degree, the hydrocarbon chain length, and the temperature of the gel‐fluid transition. For all phospholipids studied, the low‐temperature Raman spectra reveal the peaks attributed to vibrational eigenmodes of the lipid layers. Analysis of the experimental data allows us to identify the lowest eigenmodes of the bilayer, of the monolayer (leaflet), and of the hydrocarbon chain layer. In a continuum approximation, their spectral positions are determined by the ratio of the acoustic velocity and the layer thickness, although their Raman intensities depend on the interleaflet elastic coupling. Temperature dependences of the peak positions, effects of the unsaturation degree, and effects of the saline solution are considered in the work. Parameters of vibrational eigenmodes are determined by mesoscopic properties of bilayers, and the low‐wavenumber Raman spectroscopy becomes a powerful method for their description.

Biological activity of glycine and alanine derivatives of quaternary ammonium salts (QASs) against micro-organisms.

Quaternary ammonium salts (QASs) are commonly used in medicine, agriculture and industry and their wide usage caused the development of microbial resistance, thus there is still a need for new effective antimicrobial agents. Present work describes the biological activity of alanine- (DMALM-n) and glycine-derived (DMGM-n) QASs against planktonic and biofilm forms of micro-organisms. The antimicrobial activity was dependent mainly on the hydrocarbon chain length and surfactants with 12-16 atoms of carbon in the alkyl chain were the most active ones. The lowest MIC value was determined for DMALM-14 against Rhodotorula rubra and Saccharomyces cerevisiae (2·5µmoll- 1 ). Generally, alanine derivatives showed stronger effects against micro-organisms than glycine-derived QASs. Alanine-derived surfactants with 12-16 carbons in the alkyl chain had antiadhesive properties on the polystyrene surface, preventing cell attachment (about 70% of inhibition for C. albicans and 40% for S. epidermidis). Strong adhesion reduction was also observed on the stainless steel surface and the highest reduction was observed for C. albicans cells incubated on surface pretreated with DMGM-16. Moreover, DMGM-16 and DMALM-16 prevented C. albicans filamentation, one of the determinants of cell adhesion. Surfactants with C16 alkyl chain (DMGM-16 and DMALM-16) eradicated bacterial and yeast biofilm (from 60 to 90% of reduction observed after incubation of the previously grown biofilm in the presence of the highest tested concentration of the surfactant - 400µmoll- 1 ) and reduced its viability. Strong antimicrobial activity as well as antiadhesive properties make alanine- and glycine-derived QASs the potential candidates for future application as disinfectants. SIGNIFICANCE AND IMPACT OF THE STUDY: Cationic surfactants are used in many fields, among others in medicine, cosmetic and pharmaceutical industry. Their usage on a large scale caused the development of microbial resistance mechanisms to such compounds. Thus, there is a need to synthesize new surfactants with potential application as effective disinfectants to combat both planktonic and biofilm forms of micro-organisms. Present work focuses on the antimicrobial activity of chosen quaternary ammonium salts.

Supramolecular design of Benzene-1,3,5-Tricarboxamide with Hydrophobic Alkyl side chains toward long-range liquid crystalline properties

Herein we report the first approach of benzene-1,3,5-tricarboxamides (BTAs) with long-range liquid crystalline properties by utilizing hydrophobic alkyl side chains at the amide functional group. These compounds were successfully prepared in high yields by reacting 1,3,5-benzenetricarbonyl trichloride with series of aliphatic linear alkyl amines as the side chains. By increasing the length of hydrocarbon chains at the amino, thermograms of BTAs showed the formation of mesophase rangesbetween 21.8- 196.3, 41.9 - 212.4, 57.9 - 203.7, 76.1 - 207.7 and 80.5 - 200.1 degrees for decylamine, dodecylamine, tetradecylamine, hexadecylamineand octadecylamine, respectively. Such liquid crystalline properties indicate the formation of self-assembly through supramolecular interactions with a lamellar structure. In particular, benzene tricarboxamide with short alkyl chains will reduce the Van der Waals interactions to give room temperature range of mesophase structure.

Synthesis and Inhibition Behavior of the Quaternary Ammonium Salt-type Tetrameric Surfactant for Corrosion of N80 Steel in HCl Medium

The quaternary ammonium salt-type tetrameric surfactant with hydrocarbon chain length of 12 was synthesized, and characterized using FT-IR and 1H NMR. The inhibition efficiencies for N80 steel in 20% hydrochloric acid were studied by weight loss, potentiodynamic polarization method, electrochemical impedance spectroscopy at 25°C. The results obtained from weigh loss measurements show that it has good inhibitive performance. Polarization data indicates that it acts as a mixed-type inhibitor. The results obtained from EIS exhibit the protective film formed by the adsorption of surfactant molecules on metal surface. The adsorption behavior of surfactants was found to follow the Langmuir adsorption isotherm.

Measurement of the Attachment Force between an Air Bubble and a Mineral Surface: Relationship between the Attachment Force and Flotation Kinetics.

The interaction forces between air bubbles and mineral surfaces were directly measured during the attachment process using an apparatus developed in our laboratory, and they are defined as the attachment forces. The attachment forces were measured between the air bubble and mineral surfaces modified with surfactants to have different hydrophobicities. Chalcopyrite and galena were used as the mineral surfaces, and their hydrophobicity was controlled by adsorbing xanthates with different hydrocarbon chain lengths. The hydrophobicity is represented by the static contact angle of water on the mineral surface. When the static contact angle was less than 90°, the attachment force increased considerably with increasing static contact angle of the surfaces, irrespective of the mineral type or the hydrocarbon chain length of the adsorbed xanthate. The hydrophobicity of the mineral surface is found to be the dominant factor determining the attachment force. The measured attachment forces agree well with those calculated based on the force balance model derived from the capillary force and Laplace pressure equation. Microflotation experiments to examine the relationship between the attachment force and flotation kinetics were carried out under the same conditions to control surface hydrophobicity. The variation in the flotation kinetic constants and attachment forces with the water contact angle are very similar. As a result, the attachment forces measured by the developed apparatus can provide quantitative information on the interaction between an air bubble and the mineral surface and can be used for predicting the flotation kinetics.

Alkanediol-based deep eutectic solvents for isolation of terpenoids from citrus essential oil: Experimental evaluation and COSMO-RS studies

Current liquid-liquid extraction techniques for fractionation of essential oils rely on hazardous volatile organic compounds to concentrate target solutes for further food, fine chemical and medical applications. Herein, bio-renewable deep eutectic solvents based on various alkanediols were assessed as environmentally friendly alternatives to separate bioactive terpenoids from terpenes for essential oil downstream processing. In particular, DES composed of choline chloride as hydrogen bond acceptor and alkanediols including 1,3-butanediol, 2,3-butanediol, 1,2-propanediol or 1,3-propanediol as hydrogen bond donors at 1:2 ratio were used for fractionation of citrus essential oil model mixtures and real crude orange essential oil at mild conditions. The effect of the structure of alkanediols (i.e. length of hydrocarbon chain and the position of hydroxyl group) on the essential oil extraction performance provided by the different DES was explored in terms of experimental liquid-liquid equilibrium, distribution coefficients and selectivities. Additionally, the experimentally measured thermodynamic parameters were compared against those estimated using COnductor-like Screening MOdel for Real Solvents as a tool for solvent selection. Lastly, a further thermodynamic understanding of the behavior of the systems was performed by analysis of the computed sigma profiles, activity coefficients, excess enthalpies and molecular interactions between the terpenic hydrocarbon solutes and the solvents. Overall, the proposed alkanediol-based DES are feasible solvents for essential oil fractionation, arising as promising candidates to develop sustainable essential oil purification processes through selective isolation of terpenoid compounds.

Effect of alkyl chain length of amines on fluorapatite and aluminium phosphates floatabilities

Microflotation experiments and zeta potential measurements of fluorapatite, wavellite, and turquoise with the use of alkyl amines and amylopectin were conducted. The highest floatability values were achieved in the presence of dodecylamine, exceeding the floatabilities with octylamine between 30% and 90%. Above their respective isoelectric points, the phosphates reached approximately 100% of floatability with dodecylamine. The strong dependence of surfactant adsorption on hydrocarbon chain length was also evidenced by zeta potential results. In the presence of 1×10−3M dodecylamine solution, the surface charge of the phosphates changes from negative to positive until approximately pH 12, while the octylamine was not able to reverse the surface charges. The fluorapatite and wavellite floatabilities were not significantly affected by the amylopectin; however, in the presence of this depressant, the turquoise floatability, with octylamine as collector, decreases abruptly from 93% to 30%. The greater differences observed between turquoise and the other phosphates can be ascribed to their extremely complex structures, chemical composition and its dissolution in aqueous media.

Raman Spectroscopic Investigation of Olefins in Saturated Hydrocarbons and Self-Tuning Model Development

Based on systematized collection of Raman spectra of about 40 monounsaturated olefins, spectral patterns and invariant relations were established that formed the basis of the method for determining total olefins (total unsaturation per 100 carbon atoms) and their main classes in solutions of saturated hydrocarbons. Self-tuning of the model by calculating the proportion of spectrally unresolvable C=C components using the intensity of conjugated methyl groups increased its accuracy. In terms of repeatability, speed and cost-effectiveness of the analysis, the Raman-method is superior to standard methods of gas and adsorption chromatography and other modern spectralcorrelation methods. The accuracy and stability of the results repeatability is confirmed by more than annual series of parallel comparisons with the data of known method. It is shown that five types of olefins in paraffin model solutions are sufficient to construct calibration curves in units of the number of C=C bonds per 100 carbon atoms. These units make it possible to transform the data to the iodine scale and unify the calibration model for different fractions regardless of the hydrocarbon chain length. The Raman technique can be extended to analyze other mixtures of nonaromatic hydrocarbons and be used for remote control of processes via fi ber optic cables in industrial production.

Global small-angle scattering data analysis of inverted hexagonal phases.

A global analysis model has been developed for randomly oriented, fully hydrated, inverted hexagonal (HII) phases formed by many amphiphiles in aqueous solution, including membrane lipids. The model is based on a structure factor for hexagonally packed rods and a compositional model for the scattering length density, enabling also the analysis of positionally weakly correlated HII phases. Bayesian probability theory was used for optimization of the adjustable parameters, which allows parameter correlations to be retrieved in much more detail than standard analysis techniques and thereby enables a realistic error analysis. The model was applied to different phosphatidylethanolamines, including previously unreported HII data for diC14:0 and diC16:1 phosphatid-yl-ethanolamine. The extracted structural features include intrinsic lipid curvature, hydrocarbon chain length and area per lipid at the position of the neutral plane.

Aggregation behavior and reactivity of N-alkyl-N,N-dimethyl-N-(2,3-epoxy propyl) ammonium chloride

A series of epoxy-functionalized quaternary ammonium surfactants consisting of different alkyl chains (C10–C18) were synthesized. Their aggregation behaviors in aqueous solution, as well as antibacterial activity and reactivity were investigated. The cmc, γcmc, πcmc, pc20 and cmc/c20 suggested that the presence of epoxy group increased the surface activity of ADEAC. This is ascribed to the hydrogen bonding effect between the adjacent hydrophilic groups. The surface activity increased with the increase of hydrocarbon chain length. The thermodynamic parameters indicated that the micellization process was entropy-driven at high temperature, and enthalpy-driven at low temperature. The activation energy of conductance and micelle aggregation number were also calculated. The antibacterial activity of ADEAC against Gram-negative bacteria was stronger than that for Gram-positive ones, and N-dodecyl-N,N-dimethyl-N-(1,2-epoxy propyl) ammonium chloride showed the most effective antibacterial activity. The synthesis of N-hexadecyl-N,N-dimethyl-N-(1,2-epoxy propyl) ammonium chloride (HDEAC) modified chitosan demonstrated the reactivity of HDEAC.

Aggregation Behavior of Imidazolium‐Based Amino Acid Ionic Liquid Surfactants in Aqueous Solution: The Effect of Amino Acid Counterions

AbstractThree kinds of imidazolium‐based amino acid ionic liquid surfactants (AAILS), 1‐tetradecyl‐3‐methylimidazolium L‐aminopropionic acid salt ([C14mim][Ala]), 1‐tetradecyl‐3‐methylimidazolium L‐2‐pyrrolidinecarboxylic acid salt ([C14mim][Pro]), and 1‐tetradecyl‐3‐methylimidazolium L‐aminohydrocinnamic acid salt ([C14mim][Phe]), were synthesized by employing natural amino acids as counterions. Their adsorption and self‐aggregation behaviors in aqueous solution were investigated systematically by means of surface tension and electrical conductivity measurements. Surface tension results indicate that surface properties and micellization behavior of AAILS are significantly affected by counterions. The micellization of [C14mim][Pro] and [C14mim][Phe] is entropy‐driven at low temperatures but enthalpy‐driven at high temperatures, whereas [C14mim][Ala] is enthalpy‐driven throughout the whole temperature range, owing to the variation in hydrophobicity and size of amino acid counterions. The surface activity of [C14mim][Phe] is superior to that of conventional imidazolium‐based ionic liquid surfactants with the same hydrocarbon chain length, 1‐tetradecyl‐3‐methylimidazolium bromide (C14mimBr), indicating that the aromatic counterion can promote the micellar formation process.

Hydrolytic stability of aliphatic poly(carbonate-urea-urethane)s: Influence of hydrocarbon chain length in soft segment

Poly(carbonate-urethane)s (PCUs) exhibit improved resistance to hydrolytic degradation and in vivo stress cracking compared to poly(ester-urethane)s and their degradation leads to lower inflammation of the surrounding tissues. Therefore, PCUs are promising implant materials and are considered for devices such as artificial heart or spine implants. In this work, the hydrolytic stability of different poly(carbonate-urethane–urea)s (PCUUs) was studied under variation of the length of hydrocarbon chain (6, 9, 10, and 12 methylene units) between the carbonate linkages in the precursors. PCUUs were synthesized from isophorone diisocyanate and oligo(alkylene carbonate) diols using the moisture-cure method. The changes of sample weight, thermal and mechanical properties, morphology, as well as the degradation products after immersion in a buffer solution (PBS, pH = 7.4) for up to 10 weeks at 37 °C were monitored and analyzed. In addition, mechanical properties after 20 weeks (in PBS, 37 °C) were investigated. The gel content was determined based on swelling experiments in chloroform.Based on the DSC analysis, slight increases of melting transitions of PCUUs were observed, which were attributed to structure reorganization related to annealing at 37 °C rather than to the degradation of the PCUU. Tensile strength after 20 weeks of all investigated samples remained in the range of 29–39 MPa, whereas the elongation at break εm decreased only slightly and remained in the range between 670 and 800%. Based on the characterization of degradation products after up to 10 weeks of immersion it was assessed that oligomers are mainly consisting of hard segments containing urea linkages, which could be assigned to hindered-urea dissociation mechanism. The investigations confirmed good resistance of PCUUs to hydrolysis. Only minor changes in the crystallinity, as well as thermal and mechanical properties were observed and depended on hydrocarbon chain length in soft segment of PCUUs.