C8 C18 Research Articles

Mesomorphism dependence on the combined effect of molecular rigidity and flexibility

ABSTRACTA novel liquid crystalline (LC) homologous series of azoesters with a laterally substituted methoxy group RO-C6H4-COO-C6H3-(-OCH3)-N═N-C6H4-COO-C4H9(n) has been synthesized and studied with a view to understanding the effect of molecular structure on thermotropic mesomorphism. The novel homologous series consists of thirteen homologues (C1–C18). The C1–C5 homologues are nonliquid crystals. The C6 and C7 homologues are only enantiotropically nematogenic and the rest of the mesomorphic homologues (C8–C18) are enantiotropically smectogenic and nematogenic. Transition temperatures and the textures of the mesophases were determined using an optical polarizing microscope (POM) equipped with a heating stage. The novel azoester homologues were characterised and confirmed using their analytical, spectral and thermometric data. Transition curves Cr-M/I, Sm-N and N-I behaved in normal manner without (Sm-N) and with (N-I) exhibition of odd-even effect respectively in a phase diagram. Thermal stabilities for smectic and nematic are 100.0°C and 127.7°C whose, mesomorphic phase length vary from 13.0°C to 24.0°C and 11.0°C to 33.0°C, respectively. The mesomorpism is compared with other known series.

Self-assembly of aromatic biscarbamate gelators: effect of spacer length on the gelation and rheology

Low molecular weight biscarbamate organogelators (LMWBGs) with simple molecular structures that could gel different types of organic solvents were synthesized. The LMWBGs were composed of a long hydrophobic tail of linear fatty alcohol (C8–C18) and an aromatic core and could gel organic solvents such as xylene, toluene, NMP, cyclohexanol and chlorobenzene at a concentration of 10–15 mg/mL. Gelation studies indicated that the alkyl chain length residues did not affect the gelation time which was generally around 10–15 min leading to opaque gels in all the solvents. The gels in p-xylene were studied by FTIR spectroscopy and differential scanning calorimetry (DSC) for the nature of the interactions between the gelators and the solvent. FTIR spectroscopic studies revealed that hydrogen bonding and van der Waals interactions were the driving forces for the formation of the gels, while solid-state UV–visible studies revealed the existence of π–π interaction in the xerogel. The gel melting temperatures were found to decrease and then increase with increasing alkyl chain length as observed in DSC. The microscopic observations (FE-SEM) suggested that the gelator molecules self-assembled leading to nano- and microfibres in the turbid gel, and as the alkyl chain length increased, the width of the fibres increased. Rheological studies evinced the viscoelastic nature of the soft gels viscoelasticity increased with increasing gelator concentration, while fluidity increased with increasing chain length. The X-ray diffraction analysis revealed that in the xerogels from p-xylene the molecules aggregated into a layered structure. This study on the influence of alkyl side chains shows that hydrogen bonding and van der Waals interactions play a significant role in the morphology of such self-assembled structures.

Characterization of fast-pyrolysis bio-oil distillation residues and their potential applications

A typical petroleum refinery makes use of vacuum gas oil by cracking the large molecular weight compounds into light fuel hydrocarbons. For various types of fast pyrolysis bio-oil, successful analogous methods for processing heavy fractions could expedite integration into a petroleum refinery for fuel production. This paper investigated the applicability of bio-oil distillation residues (i.e., ‘bottoms’) toward end-use and/or post-processing through the use of various physical and chemical characterization methods, including FTIR, NMR and their decomposition in a micropyrolyzer (Py–GC–MS). We compared distillate bottoms from both the recently developed tail-gas reactive pyrolysis (TGRP) and traditional pyrolysis bio-oils, emanating from switchgrass and horse manure feedstocks. Based on the FTIR and NMR measurements, we found the traditional bio-oil bottoms to contain more reactive functional groups, whereas TGRP bottoms are highly aromatic and exhibit a lack of functional groups. Manure-based bottoms consistently contained more aliphatic carbons than those of switchgrass origin. However, irrespective of the origin of the feedstock, all bottoms samples possessed high HHVs making them suitable for solid fuel application, such as direct combustion (30MJ/kg for traditional bio-oil bottoms; 37MJ/kg for TGRP bottoms). A preliminary evaluation using Py–GC–MS to test their suitability for use in refinery cracking processes revealed that the TGRP-based bottoms all produced significant yields of pyrolyzate (20–50%), with nearly all detected compounds comprising alkyl benzenes and alkyl phenols. However, the manure-based TGRP bottoms produced a higher proportion of C8–C18 paraffin compounds.

Lipophilicity of porphyrins and their retention in IAM, C8–C18 and HILIC chromatographic systems

Porphyrins are a class of photosensitizers used in photodynamic therapy (PDT). Understanding the interaction of porphyrins with membrane cells components is important in order to improve this therapy. Many analytical methods can be used for this aim. High performance liquid chromatography (HPLC) was used for the separation of porphyrins on RP and HILIC stationary phases as well as on a biomimetic membrane IAM phase. Twenty-six tetraphenyl porphyrins (TPP) were successfully separated on an IAM column, a C18 Gravity RP column, a C8 Gravity RP column, a PolarTec RP column and a HILIC column. Stationary phases were chosen as the most appropriate to cover the study of different types of interactions. Elution was performed with a 45min linear gradient. Obtained gradient retention times were converted to gradient chromatography hydrophobicity index (CHI) and to an apparent retention factor (kapp). The partition coefficients (logP) of the 26 compounds were measured in a 2-octanol/PBS system and estimated in silico. Correlation between kapp values was studied. Moreover, a multivariate analysis was performed to explain columns relationships. Obtained results show that porphyrins are separated mainly according to hydrophobic interactions that are relative to their structure (sugar number and the disposition around the porphyrin macrocycle).

Preliminary experimental study on biofuel production by deoxygenation of Jatropha oil

Deoxygenation through decarboxylation of Jatropha curcas (non-edible) oil under a nitrogen atmosphere was performed using alumina (Puralox SBa200) and hydrotalcite (Pural MG70) as catalysts at 350 and 400°C. In general, liquid product yields obtained exceeded 80%. FTIR spectroscopy showed that the oxygen contained in the liquid product decreases significantly when hydrotalcite is used as the catalyst with a reaction time of 6h. At the end of the tests, a liquid biofuel was produced with a high proportion of hydrocarbons – around 83% – of mainly C8–C18. The product also showed good properties as a heating value of around 44MJ/kg, higher than biodiesel (40MJ/kg) and near to diesel (46MJ/kg), and a lower viscosity (4cSt) than biodiesel (4.5cSt). Using GC analysis it was possible to identify the CO2 and CO as the principal compounds present in the reaction gas, confirming that oxygen is removed mainly through decarboxylation and decarbonylation reactions.

Self-assembly and emulsification properties of hydrophobically modified inulin.

A series of alkenylated inulin samples were synthesized in aqueous solution using alkenyl succinic anhydrides with varying alkenyl chain lengths (C8-C18). The inulin derivatives (ASA-inulins) were characterized using NMR and FTIR and their degree of substitution determined. The solution properties of ASA-inulins were investigated using dye solubilization, surface tension, and dynamic light scattering, and all three techniques confirmed that the molecules aggregated in solution above a critical concentration (critical aggregation concentration, CAC). The value of the CAC was found to be reasonably consistent between the different techniques and was shown to decrease with increasing alkenyl chain length, from 0.08% for the octenyl succinylated sample to 0.005% for the octadecenyl succinylated sample. The hydrodynamic diameter of ASA-inulins above the CAC was determined from dynamic light scattering studies and was shown to increase with alkenyl chain length, from 4 nm for the octenyl derivative to 55 nm for the hexadecenyl derivative. All ASA-inulins were shown to be able to produce oil-in-water emulsions with a droplet size similar to that of emulsions prepared using Tween 20 on storing for 21 days. The fact that the derivatives are able to form micellarlike aggregates and stabilize emulsions makes them suitable candidates for the encapsulation and delivery of water-insoluble active compounds, with potential application in food, cosmetic, personal care, and pharmaceutical formulations.

A novel method to synthesize 1‐acyl‐sn‐glycero‐3‐phosphocholine and 1,2‐diacyl‐sn‐glycero‐3‐phosphocholine

A facile, efficient, solvent‐free method for the synthesis of phosphocholines and lyso phosphocholines in excellent yields has been developed employing sn‐glycero‐3‐phosphocholine‐kieselguhr complex with shorter reaction times with the recycling of kieselguhr for further use. Fatty acids with chain lengths C3–C6 and C8–C18 formed 1,2‐diacyl‐sn‐glycero‐3‐phosphocholines and 1‐acyl‐sn‐glycero‐3‐phosphocholines respectively. Fatty acid chlorides (C3–C18) resulted exclusively in 1,2‐diacyl‐sn‐glycero‐3‐phosphocholines.Practical applications: Synthetic methodology for the synthesis of symmetrical phosphatidylcholines is described. The described method uses kieselguhr as a catalyst and reagent which can be recycled after the reaction. By this method gram quantities of phosphatidylcholines can be prepared without the use of any other acylating reagents. The synthetic method is a novel approach for producing phosphatidylcholines and lysophosphatidylcholines which have wide range of applications.Synthesis of 1‐acyl‐sn‐glycero‐3‐phosphocholine and 1,2‐diacyl‐sn‐glycero‐3‐phosphocholine.

Efficient Control of the Rheological and Surface Properties of Surfactant Solutions Containing C8–C18 Fatty Acids as Cosurfactants

Systematic experimental study is performed about the effects of chain length (varied between C8 and C18) and concentration of fatty acids (FAc), used as cosurfactants to the mixture of the anionic surfactant SLES and the zwitterionic surfactant CAPB. The following properties are studied: bulk viscosity of the concentrated solutions (10 wt % surfactants), dynamic and equilibrium surface tensions, surface modulus, and foam rheological properties for the diluted foaming solutions (0.5 wt % surfactants). The obtained results show that C8-C10 FAc induce formation of wormlike micelles in the concentrated surfactant solutions, which leads to transformation of these solutions into viscoelastic fluids with very high apparent viscosity. The same FAc shorten the characteristic adsorption time of the diluted solutions by more than 10 times. In contrast, C14-C18 FAc have small effect on the viscosity of the concentrated solutions but increase the surface modulus above 350 mN/m, which leads to higher friction inside sheared foams and to much smaller bubbles in the formed foams. The intermediate chain C12 FAc combines some of the properties seen with C10 FAc and other properties seen with C14 FAc. These results clearly demonstrate how appropriate cosurfactants can be used for efficient control of the rheological properties of concentrated surfactant solutions and of some important foam attributes, such as bubble size and foam rheology.

Zirconium phenyl phosphonate phosphite as a highly active, reusable, solid acid catalyst for producing fatty acid polyol esters

The application of zirconium phenyl phosphonate phosphite (ZrPP) as a solid acid catalyst for producing polyol esters by esterification of glycerol or trimethylolpropane with a fatty acid (C8–C18.1) is reported for the first time. ZrPP exhibits high catalytic activity and in particular, (di+tri) esters selectivity (92.3mol%). These esters of polyols are known for their application as biolubricants. The catalyst prepared using phosphorous acid to phenyl phosphonic acid molar ratio of 3:1 was found superior. The influence of process parameters on activity and selectivity of the catalyst was investigated. ZrPP was reusable in at least three recycling experiments. Hydrophobicity due to exposed phenyl groups on the surface is the possible cause for superior esterification activity of this novel, solid catalyst.

Correction to “Evaporation Rates and Vapor Pressures of the Even-Numbered C8–C18 Monocarboxylic Acids”

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionORIGINAL ARTICLEThis notice is a correctionCorrection to “Evaporation Rates and Vapor Pressures of the Even-Numbered C8–C18 Monocarboxylic Acids”Christopher D. Cappa*, Edward R. Lovejoy, and A. R. RavishankaraCite this: J. Phys. Chem. A 2013, 117, 10, 2285Publication Date (Web):February 28, 2013Publication History Published online28 February 2013Published inissue 14 March 2013https://doi.org/10.1021/jp4017213Copyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views373Altmetric-Citations-LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (111 KB) Get e-Alerts Get e-Alerts

Fast and sensitive UHPLC methods with fluorescence and tandem mass spectrometry detection for the determination of tetracycline antibiotics in surface waters

In this paper two fast and highly sensitive ultra-high performance liquid chromatography (UHPLC) methods for the determination of tetracycline antibiotics (oxytetracycline, tetracycline, doxycycline, demeclocycline, chlortetracycline, minocycline and degradation product epitetracycline) in surface waters have been developed using fluorescence (FL) and mass spectrometry (MS) detection. ACQUITY UPLC BEH C8 and ACQUITY CSH C18 columns were employed for FL and MS detection, respectively, both packed with 1.7μm particles. Mixed-mode separation mechanism of CSH (charged surface technology) sorbent was found particularly useful in analysis of TCs, which possess problematic amphoteric structures. The FL methodology was based on chelation of tetracyclines with calcium ions to perform on-column derivatisation. The developed methods were compared in the terms of validation parameters including linearity, sensitivity, precision and accuracy. The linearity range for FL detection was within 7ngmL(-1) to 50μgmL(-1) with method limit of detection (MLOD) as low as 0.2ngmL(-1) for most of the analytes. MS detection showed even higher sensitivity reaching MLOD of 0.003ngmL(-1), which is the highest sensitivity reported so far in analysis of TCs. Matrix matched calibration curves in the range of 0.01-50ngmL(-1) were used for quantification to compensate for matrix effects with the correlation coefficients demonstrating good linearity (0.9940-0.9999). The extraction of the antibiotics from surface waters was performed using solid phase extraction with Oasis HLB cartridges. Accuracy was expressed as recovery with values ranging from 96.52% to 127.30% and from 91.66% to 123.70% for FL and MS detection, respectively.

Carboxylic acid reductase is a versatile enzyme for the conversion of fatty acids into fuels and chemical commodities

Aliphatic hydrocarbons such as fatty alcohols and petroleum-derived alkanes have numerous applications in the chemical industry. In recent years, the renewable synthesis of aliphatic hydrocarbons has been made possible by engineering microbes to overaccumulate fatty acids. However, to generate end products with the desired physicochemical properties (e.g., fatty aldehydes, alkanes, and alcohols), further conversion of the fatty acid is necessary. A carboxylic acid reductase (CAR) from Mycobacterium marinum was found to convert a wide range of aliphatic fatty acids (C(6)-C(18)) into corresponding aldehydes. Together with the broad-substrate specificity of an aldehyde reductase or an aldehyde decarbonylase, the catalytic conversion of fatty acids to fatty alcohols (C(8)-C(16)) or fatty alkanes (C(7)-C(15)) was reconstituted in vitro. This concept was applied in vivo, in combination with a chain-length-specific thioesterase, to engineer Escherichia coli BL21(DE3) strains that were capable of synthesizing fatty alcohols and alkanes. A fatty alcohol titer exceeding 350 mg·L(-1) was obtained in minimal media supplemented with glucose. Moreover, by combining the CAR-dependent pathway with an exogenous fatty acid-generating lipase, natural oils (coconut oil, palm oil, and algal oil bodies) were enzymatically converted into fatty alcohols across a broad chain-length range (C(8)-C(18)). Together with complementing enzymes, the broad substrate specificity and kinetic characteristics of CAR opens the road for direct and tailored enzyme-catalyzed conversion of lipids into user-ready chemical commodities.

Synergistic effect of alkyl-O-glucoside and -cellobioside biosurfactants as effective emulsifiers of crude oil in water. A proposal for the transport of heavy crude oil by pipeline

Alkyl-O-glucoside and -cellobioside biosurfactants were synthesized with a long fatty chain (C8–C18) in order to prepare stable and low viscous oil-in-water (O/W) emulsions of a Mexican heavy crude oil. The resulting O/W emulsions, prepared with a single alkyl-O-glucoside or alkyl-O-cellobioside, were very unstable and broke out. Only the use of tetradecyl-O-cellobioside allowed the formation of a poor stable complex emulsion with the broader particle size distribution and more viscous than other emulsions. Nonetheless, we observed a synergistic effect when a biosurfactant mixture was used and the resulting emulsions were stable for several days while water separation occurred constantly within 40days in static conditions. The mixture of biosurfactants with a pC20 value higher than 4.0 and a CMC/C20 ratio higher than 1.0 favored the formation of a less viscous, narrow particle size distribution and thermal stable O/W emulsion. This feature is remarkable important when we look for the pipeline transportation of heavy and extra-heavy crude oils as O/W emulsions. In this work, we present the characterization of biosurfactants as well as the formulation and properties of O/W emulsions of a Mexican heavy crude oil.

Improved acylation of phytosterols catalyzed by Candida antarctica lipase A with superior catalytic activity

This work reported a novel approach to synthesize phytosterol (β-sitosterol as a model) fatty acid esters by employing Candida antarctica lipase A (CAL A) which shows a superior catalytic activity to other lipases. A series of β-sitosteryl fatty acid esters (C2–C18) have been successfully prepared with structural identification of products by 1H NMR and Fourier transform-infrared spectroscopy (FTIR). Compared to other immobilized lipases, CAL A achieves 6–14 times faster esterification of β-sitosterol with myristic acid. CAL A shows low activity toward short chain fatty acids (C2–C6), and remarkably high activity for medium and long chain ones (≥C8). Reaction time, temperature, enzyme load, substrate ratio and concentration, and solvent property are found to profoundly influence reaction rates. A pronounced correlation between enzyme activities and logP values of solvents, among the solvents with a broad spectrum of logP values, was observed. 93–98% yield of β-sitosteryl esters could be achieved with hexane as solvent, fatty acid (C8–C18)/β-sitosterol (1:1, mol:mol), 5–10% CAL A load at 40–50°C for 24h. This work demonstrated the promising potential of CAL A in bioprocess of phytosterols for value-added application.

Surface Activity and Cleavability of Gemini Surfactants Featuring Hydrophilic Spacer Groups

AbstractIn this study we prepared and characterized a series of novel ester‐linked gemini surfactants, featuring ester bonds in their structures, through the reactions of polyethylene glycol (PEG400) with various fatty acids (C8–C18). These gemini surfactants exhibit excellent surface activities, as evidenced by their surface tension, wetting power, and low‐foaming and buffer abilities. We examine the influence of the concentrations of the ester‐linked gemini surfactants on the surface tension, from which we obtain the critical micelle concentrations. Under basic conditions, each of these cleavable surfactants decomposes into a water‐insoluble fatty acid and two water‐soluble products; in contrast, they are stable under neutral and acidic conditions.

Synthesis and physicochemical properties of nonionic Gemini surfactants with a sulfonate spacer

We have prepared a series of novel nonionic Gemini surfactants, featuring sulfonate spacers, from maleic anhydride (MA), polyethylene glycol (PEG400), sodium hydrogen sulfite, and various fatty acids (C8–C18). We measured the surface activities of these compounds in terms of the critical micelle concentration (CMC), the surface tension at the CMC ( γ cmc), the surface excess concentration ( Γ cmc), the surface area occupied per molecule ( A cmc), and the standard free energy of micellization per mole of monomer unit (Δ G° m). We used pyrene fluorescence spectroscopy to characterize the hydrophobicity of the aggregates of nonionic Gemini surfactants. We measured the CMCs from the intensity ratio of the emission of pyrene in the nonionic Gemini surfactant solutions. In addition, we studied the surface activity in terms of the emulsification of 10% (w/w) olive oil in nonionic Gemini surfactant solutions. Shorter hydrophobic chains provided more-stable emulsions.

Synthesis and Physical Properties of Estolide Ester Using Saturated Fatty Acid and Ricinoleic Acid

A study was conveyed to produce estolide ester using ricinoleic acid as the backbone. The ricinoleic acid reacted with saturated fatty acid from C8–C18. These reactions were conducted under vacuum at 60°C for 24 h without solvent. The reaction used acid catalyst, sulphuric acid. The new saturate ricinoleic estolide esters show superior low-temperature properties (−52 ± 0.08°C) and high flash point (>300°C). The yield of the neat estolide esters ranged from 52% to 96%. The viscosity range was 51 ± 0.08 to 86 ± 0.01 cp. These new saturated estolide esters were also compared with saturated branched estolide esters.

Preparation and antimicrobial activity of Konjac Glucomannan modified with quaternary ammonium compound

AbstractSeven kind of graft copolymerization Konjac Glucomannan with quaternary ammonium group have been prepared, using Konjac Glucomannan (KGM) and methacryloxylethyl alkyl dimethyl ammonium bromide with c8–c18 alkyl and benzyl in water, ceric ammonium nitrate as initiator, the reaction temperature of 348 K, and the reaction period of 3 h. The structures were confirmed by FTIR. The 15 min inhibitory rates of all the graft copolymerization KGM against Escherichia coli and Staphylococcus aureus reached 99.99%, against Candida albicans somewhat lower, but 30 min inhibitory rate still reached 99.02% for graft copolymerization KGM with quaternary ammonium group having 14 alkyl. The antibacterial mechanism of the graft copolymerization KGM has been investigated by adsorption ability to E. coli, measure of 260 nm absorbing materials and SEM micrographs. Firstly, the bacteria were fastly adsorbed by graft copolymerization KGM. Interactions between bacterial membranes and antibacterial product cause fundamental changes in both membrane structure and function, induced leakage of cytoplasmic contents is a classic indication of damage to the bacterial cytoplasmic membrane. The loss of the connection between the outer membrane and the underlying peptidoglycan induces the abnormality of nodular structures and bleb formation of the cell envelope of E. coli. The antibacterial mechanism is in accordance with microbiologic findings identifying surface blebbing as the first morphologic change occurring in the permeability barrier of gram‐negative bacteria under mild heat stress and laser irradiation, etc. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

ChemInform Abstract: Stereoselective Synthesis Towards the C8-C18 Subunit of Pamamycin-607 Induced by a Chiral Sulfoxide Group.

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ChemInform Abstract: Diastereodivergent Synthesis of the C8-C18 Precursor and C1′-C11′ Subunit of Pamamycin 607 Induced by a Chiral Sulfoxide Group.

Abstract A key step in obtaining the C8–C18 and C1′–C11′ fragments of pamamycin 607, which differ by the syn- and anti-configuration of one chiral center α to the tetrahydrofuran ring, was the chelation controlled E–Z-isomerization of the substituted vinyl tetrahydrofuran intermediate 3a which has so far been obtained only in the more stable E-configuration.