Presence Of Different Alcohols Research Articles

Amine-Imine Tautomeric Excited State Intramolecular Proton Transfer in Metal-Organic Frameworks: Alcohol and Anion Recognition.

To study the amine-imine tautomeric alteration through excited state intramolecular proton transfer (ESIPT), three amine-functionalized metal-organic frameworks (MOFs) have been synthesized by using two different metal ions and neutral linkers along with same ESIPT-enable anionic linker through the slow diffusion process. All the MOFs have 2D structure with asymmetric units of {[Mn(2,6-dip)(2-atp)](H2O)(CH3OH)}n(1), {[Mn(3,5-dip)(2-atp)](solvent)x}n(2) and {Zn2(3,5-dip)2(2-atp)(μ2-O2-)](solvent)x}n(3) (where 2,6-dip = 2,6-di(1H-imidazol-1-yl)pyridine, 3,5-dip = 3,5-di(1H-imidazol-1-yl)pyridine, 2-atp = 2-amino terephthalic acid). The 2D networks of desolvated form of compound 1, 2, and 3 show water influencing proton transfer for amine-imine tautomerism in excited state through the ionic interaction with water molecules to the frameworks. However, in case of polar small chain aliphatic alcohols like methanol, ethanol and isopropanol; the compounds does not show any dual emissive ESIPT but exhibit three different intensified single peaks for each of the compounds. This different emission intensity in presence of different alcohols are helpful to detect these alcohols selectively. In addition to that in case of all three compounds, the water assisted-ESIPT is interrupted by some strong oxidizing agents like CrO42-, Cr2O72- and MnO4- ions. This phenomenon allows the method of detection for the aforesaid oxidizing ions in water by interruption of the dual emissive fluorescence.

Aggregation behavior, interaction forces and physico-chemical parameters of cetyltrimethylammonium chloride in aqueous solution of bovine serum albumin: Impacts of short-chain alcohols and temperature

To better understand the molecular interactions between cetyltrimethylammonium chloride (CTAC) and bovine serum albumin (BSA), we report the alteration of the physicochemical characteristics of CTAC in aqueous BSA solutions in the presence of different alcohols. The analyses were performed using the conductivity method at temperatures ranging from 298.15 to 323.15 K, with 5 K intervals. The critical micelle concentration (CMC) values of the BSA + CTAC systems were found to change with variations in alcohol types, solvent compositions, and temperatures. The CMC values grew with the rising of alcohol contents. The negative free energy changes (∆Gm0) indicated the spontaneous association of the systems in all solvents media. The magnitudes of ∆Hm0 and ∆Sm0, determined from the micellization of the systems, indicated the presence of electrostatic, ion-dipole, and hydrophobic forces. The thermodynamics of transfer (free energy (∆Gm,tr0), enthalpy (∆Hm,tr0), entropy (∆Sm,tr0)), and compensation parameters (∆Hm0,∗ and Tc)—were also calculated, which provided significant insights into the potential interactions between CTAC and BSA in the presence of various alcohol additives. Furthermore, molecular docking studies suggested the binding of CTAC to different BSA binding sites with varying affinities.

Towards electrochemical hydrogen storage in liquid organic hydrogen carriers via proton-coupled electron transfers

Green hydrogen is identified as one of the prime clean energy carriers due to its high energy density and a zero emission of CO2. A possible solution for the transport of H2 in a safe and low-cost way is in the form of liquid organic hydrogen carriers (LOHCs). As an alternative to loading LOHC with H2 via a two-step procedure involving preliminary electrolytic production of H2 and subsequent chemical hydrogenation of the LOHC, we explore here the possibility of electrochemical hydrogen storage (EHS) via conversion of proton of a proton donor into a hydrogen atom involved in covalent bonds with the LOHC (R) via a proton-coupled electron transfer (PCET) reaction:2nH++2ne-+Rox↔nH20Rred. We chose 9-fluorenone/fluorenol (Fnone/Fnol) conversion as such a model PCET reaction. The electrochemical activation of Fnone via two sequential electron transfers was monitored with in-situ and operando spectroscopies in absence and in presence of different alcohols as proton donors of different reactivity, which enabled us to both quantify and get the mechanistic insight on PCET. The possibility of hydrogen extraction from the loaded carrier molecule was illustrated by chemical activation.

Effect of sacrificial agents on the photoelectrochemical properties of titanium dioxide co-doped with tungsten and manganese as new visible light active

By using one-step anodizing, W–Mn–TiO2 nanotubes (W–Mn–TNTs) were synthesized in different ratios of two metals. The surface morphology and structure of the W–Mn–TNTs samples were characterized by FE-SEM, XRD, EDAX-mapping, and the optical features of the samples were studied by UV–Vis. The photoelectrochemical behavior of the samples was investigated by linear sweep voltammetry, chronoamperometry, and open-circuit potential. The obtained results showed the new doped synthesized samples have better photoelectrochemical properties compared to the bare TiO2. The K2 sample (synthesized in anodizing solution containing 9 mM Na2O4W and 3 mM KMnO4) showing the best result compared to the others, was examined in the presence of different alcohols as sacrificial agents in photoelectrochemical cells water splitting. The glycerol demonstrated a better result than the rest samples.

Fully catalytic upgrading synthesis of 5-Ethoxymethylfurfural from biomass-derived 5-Hydroxymethylfurfural over recyclable layered-niobium-molybdate solid acid

Biomass-derived resources exploited in depth toward the synthesis of high value-added chemicals is very promising, but still limited by the applicable catalyst. In this paper, we report regulated robust multilayer-like polyoxometalates(Niobium molybdate) specific to the catalytic synthesis of promising 5-Ethoxymethylfurfural (EMF). The present solid acid catalysts resulted from precisely-tuned compositions of Nb and Mo toward acquiring controlled Brønsted acid amounts and interlayer space coupling with specific Lewis acid sites are demonstrated to be the determining factors for tuning conversion and selectivity in the synthesis of EMF, respectively. The characterization results indicate that the increment in Nb moiety is beneficial to produce more accessible acid sites and the enlarged interlayer space in the catalyst, thereby promoting the acid-catalyzed conversion. As a result, the full conversion(Conv. 100%) of 5-hydroxymethylfurfural into the 5-Ethoxymethylfurfural (Select. >99%) by etherification with ethanol within only 60 min was realized as the record-high yield under the solvent-free condition, far outperforming several traditional catalysts. In addition, the rational 67% yield of EMF was received when using fructose as an initial reactant. Ulteriorly, the resultant catalyst inherits the superior catalytic activity in the substrate expansion experiments in the presence of different alcohols. More importantly, the resulted catalyst shows durable catalytic activity without any activity-loss during the eight recycling, which reveals the huge potential industrial application prospect.

Dynamics of radiolytic formation of CdSe quantum dots in aqueous solution containing different alcohols: A pulse radiolysis study

The dynamics of radiolytic formation of CdSe quantum dots in aqueous solution containing equimolar ammoniated cadmium sulphate, Cd(NH3)4SO4 and sodium selenosulphate, Na2SeSO3 as precursors for Cd and Se respectively, have been investigated in the presence of different aliphatic alcohols, namely methanol, ethanol, 1-propanol, 2-propanol or 1-butanol by electron pulse radiolysis studies. The mechanism of CdSe quantum dots formation was studied in N2O saturated aqueous solutions to investigate the formation through reactions with different aliphatic alcohols. The formation of the CdSe quantum dots was found to proceed via the formation of short lived transient intermediate species having and absorption at around 500 nm, which are formed through the reaction of different aliphatic alcohol radicals with the cadmium and selenium precursors. The rate constants for the formation and decay of these intermediate species have been determined. Optical properties of these quantum dots were found to be different in the presence of different alcohols.

Hydrodynamics of Pilot Plant Scale Airlift Reactor in Presence of Alcohols

Abstract The overall gas hold-up of a pilot plant scale internal loop airlift reactor was studied in presence of different alcohols in varied concentration. It has been observed that these simple alcohols can enhance overall gas hold-up of the airlift assembly possibly due to formation of protective thin layer over smaller gas bubbles thereby reducing chance of their coalescence. As the alcohols can be used as food source for the micro organisms present in the system, this green and environment friendly process have potential to replace usage of hazardous surfactants often used for enhancing overall hold-up in order to obtain desired mass transfer characteristics. An empirical relationship encompassing overall gas hold-up of the reactor as a function of superficial gas velocity and alcohol concentration is also developed.

Comparative study of alcohols as sacrificial agents in H2 production by heterogeneous photocatalysis using Pt/TiO2 catalysts

Abstract In this work, a TiO 2 photocatalyst synthesized using a sol–gel procedure (SG750) was Pt modified through photodeposition (SG750-2.1 wt%Pt) and tested for its efficiency in hydrogen production by heterogeneous photocatalysis in the presence of different alcohols as sacrificial agents. The tested alcohols were: methanol, ethanol, ethyleneglycol and glycerol. Production was continuously followed for 3.5 h. The concentration of each alcohol that resulted in the highest production was optimized and some of the degradation intermediates were identified and quantified in both gaseous and the remaining liquid phase at the end of the process. Optimum concentrations were found to be around 17.13 M for methanol and 7.34 M for ethanol, ethyleneglycol and glycerol. In terms of sacrificial agent used, hydrogen production was as follows: methanol > ethanol > ethyleneglycol > glycerol. The stability of the photoactivity of the catalyst was demonstrated through reuse cycles with 0.011 M of sacrificial agent and was also compared with that of commercial photocatalysts, in this case Aeroxide TiO 2 P25 and Hombikat UV-100, with the same photodeposited Pt%.

Mechanism of alcohol-enhanced lucigenin chemiluminescence in alkaline solution.

The chemiluminescence (CL) of lucigenin (Luc(2+)) can be enhanced by different alcohols in alkaline solution. The effect of different fatty alcohols on the CL of lucigenin was related to the carbon chain length and the number of hydroxyl groups. Glycerol provides the greatest enhancement. UV/Vis absorption spectra and fluorescence spectra showed that N-methylacridone (NMA) was produced in the CL reaction in the presence of different alcohols. The peak of the CL spectrum was located at 470 nm in all cases, indicating that the luminophore was always the excited-state NMA. The quenching of lucigenin CL by superoxide dismutase (SOD) and the electron spin resonance (ESR) results with the spin trap of 5,5-dimethyl-1-pyrroline N-oxide (DMPO) demonstrated that superoxide anions (O2 (•-)) were generated from dissolved oxygen in the CL reaction and that glycerol and dihydroxyacetone (DHA) can promote O2 (•-) production by the reduction of dissolved oxygen in alkaline solution. It was assumed that the enhancement provided by different alcohols was related to the solvent effect and reducing capacity. Glycerol and DHA can also reduce Luc(2+) into lucigenin cation radicals (Luc(•+) ), which react with O2 (•-) to produce CL, and glycerol can slowly transform into DHA, which is oxidized quickly in alkaline solution.

Esterification of oleic acid using 12-tungstophosphoric supported in flint kaolin of the Amazonia

In this study, 12-tungstophosphoric acid was supported in different proportions, 20, 40 and 60wt%, using as a matrix of the Amazon kaolin flint and century (commercial kaolin) via impregnation in aqueous solution (HCl 0.1 and 0.5molL−1) and acetonitrile. Before the impregnation, kaolin were subjected to a leaching acid in order to increase surface area and acidity. For characterization of the catalysts, FT-IR, XRD and XRF were employed. The FT-IR analysis showed that there was no decomposition of the HPW Keggin structure during material preparation. However, in the presence of HCl 0.1molL−1, it was not possible to conclude that the impregnation was due to the low intensity of the absorptions for the HPW; for the spectra with acetonitrile and HCl 0.5 it was possible to observe them. The XRF and XRD data confirmed these results. The catalysts were tested in the esterification reaction using molar ratio alcohol: acid equal to 30 at 100°C for 2h in a PARR 4348 reactor in the presence of different alcohols. Best conversions were obtained with the use of methanol, reaching 97.21% yield, independent of HPW support. A study of reaction parameters, temperature and time with the catalyst PW(20)MFS and 20wt% concentration of HPW in metakaolin flint (with and without acid treatment) was also conducted. It was observed that the catalyst deactivation occurred by coke formation, since leaching was about 2%.

Dispersion of carbon nanotubes by the branched block copolymer Tetronic 1107 in an alcohol–water solution

The dispersion of carbon nanotubes (CNTs) by the branched block copolymer Tetronic 1107 was investigated in mixed solvents consisting of water and one of the following alcohols: ethanol, n-propanol, ethylene glycol (EG), or glycerol (GLY). The maximum concentration of dispersed CNTs (Climit) and the optimum T1107 concentration (Copt) to disperse the maximum amount of CNTs in different solvents were obtained from UV–vis–NIR absorbance spectra. The addition of ethanol or n-propanol to water dramatically increases the Climit. The value of Copt follows the order: n-propanol–water > ethanol–water > EG–water ≈ GLY–water mixtures. ID/IG was used to characterize the defect density of CNTs dispersed in the mixed solvents, which was investigated by Raman spectroscopy. The ID/IG values in n-propanol–water and ethanol–water mixtures are higher than those in EG–water and GLY–water mixtures. High-resolution transmission electron microscopy is used to confirm a favorable dispersion in the presence of different alcohols.

Activity of PtSnRh/C nanoparticles for the electrooxidation of C1 and C2 alcohols

A systematic investigation of alcohol adsorption and oxidation on binary and ternary electrocatalysts in acid medium was performed. Binary (PtRh) and ternary (PtRhSn) were prepared by the Pechini modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by energy dispersive X-ray and X-ray diffraction (XRD) techniques. The XRD results showed that the Pt80Rh20/C and Pt70Sn10Rh20/C electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/Rh and Pt/Sn.Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5moldm−3 H2SO4), and in the absence and presence of different alcohols (methanol, ethanol and ethylene glycol). The electrochemical results obtained at room temperature have shown that the Pt70Sn10Rh20/C catalyst display better catalytic activity for alcohol oxidation compared with the binary catalyst.In situ reflectance infrared spectroscopy measurements have shown that the oxidation of alcohols mentioned produced CO2 at low potentials indicating that the materials synthesized could be used as efficient anodes in the fuel cell applications.

ChemInform Abstract: Palladium‐Catalyzed Regioselective Aerobic Oxidative C—H/N—H Carbonylation of Heteroarenes under Base‐Free Conditions.

AbstractUsing air as oxidant and a balloon pressure of CO, indoles, thiophenes and benzothiophenes are converted in the presence of different alcohols into carboxylic acid esters.

Novel Cyclopalladated Imino-thiophenes: Synthesis and Reactivity Toward Alkynes and Carbon Monoxide

ortho-palladated complexes based on thiophene and benzothiophene ligands 1a and 1b have been synthesized by direct C-H activation under mild conditions. These species were fully characterized, including single-crystal X-ray diffraction analysis. The reactions of these novel complexes with internal alkynes afforded a variety of thieno[3,2-c]pyridinium salts substituted at the 6- and 7-positions. The thiophene-based complex 2a also reacts with carbon monoxide, in the presence of different alcohols, forming the corresponding esters by tandem alkoxycarbonylations. This latter reaction can be exploited for the unexpected, but straightforward, formation of the monomeric bis-cyclometallated complexes 6a and 6b from 2a or 2b, whose syntheses do not require the employment of transmetallating agents. The structures of these monomeric palladacycles were also fully elucidated by means of X-ray diffraction studies.

Palladium‐Catalyzed Regioselective Aerobic Oxidative CH/NH Carbonylation of Heteroarenes under Base‐Free Conditions

Using air as oxidant and a balloon pressure of CO, indoles, thiophenes and benzothiophenes are converted in the presence of different alcohols into carboxylic acid esters.

Application of 29Si NMR spectroscopy to study of alkaline aqueous and alcoholic tetraoctylammonium (TOA) silicate solutions

29Si NMR spectroscopy is a powerful tool for studying the silicate species existing in aqueous and non-aqueous solutions. In the present work, 29Si NMR spectroscopy is used to characterize the species present in alkaline alcoholic solutions of silicates. Tetraoctylammonium (TOA) hydroxide is used as a template. The effects of polymerization/depolymerization of silicate anions on alkaline alcoholic solutions are investigated using different alcohols (methanol, 1-propanol, 1,3-propane-diol, and glycerin) by 29Si NMR spectroscopy. The esterification of monomeric silicate, Si(OH) 4, in the presence of different alcohols is also studied. Esterification of Si(OH) 4 depends on the alkyl chain as well as the number of hydroxyl groups present in the alcohol.

Bagasse from the mezcal industry as an alternative renewable energy produced in arid lands

In the mezcal industry, the xerophyte A gave salmiana is used to produce mezcal, and neither the plant nor its residues have been studied before as an alternative source of fuel. Bagasse and wasted fibers samples from alcoholic beverage production were collected in order to find out their properties as fuel. Another sample consists in pyrolyzed bagasse at 450 °C to produce carbon. DSC results revealed differences in the heat of combustion values, where pyrolyzed bagasse (19.36 MJ/kg) had a higher value than bagasse (9.55 MJ/kg) or the fiber (8.4 MJ/kg). SEM images showed the morphological changes in the fibers after their processing. TGA analysis showed the presence of different alcohols impregnated on the bagasse, which allows for an increase in heat of combustion. With these preliminary results it can be seen that it is possible to use the byproducts generated by the alcoholic beverage production as an alternative source of fuel.

The Binding Behavior of Cyclodextrins toward a Nitroxide Spin Probe in the Presence of Different Alcohols As Studied by EPR

Stability constants, rates of association and dissociation, and thermodynamic and activation parameters for the formation of inclusion complexes between the radical guest, N-benzyl- tert-butyl- d 9-nitroxide and beta- or 2,6- O-dimethyl-beta-cyclodextrin (CDs), have been determined by EPR spectroscopy in water in the presence of 14 different alcohols, differing in size and lipophilicity. In all cases, it was found that addition of alcohol, depending on its structure and concentration, causes a reduction of the stability of the paramagnetic complex. Global analysis of EPR data allowed us to explain the CDs binding behavior: we discarded the formation of a ternary complex, where alcohol and radical guest are coincluded into CD cavity, while data were found more consistent with the formation of a binary complex alcohol:CD competing with the monitored complex nitroxide:CD. Both kinetic and thermodynamic analysis of the experimental results have revealed that the presence of alcohols affects to a larger extent the dissociation rather then the association of radical probe and CD and that the former process is of greater importance in determining the stability of the complex, this confirming the reliability of the competition model proposed. This competition has been used for the indirect determination of the stability constants of complexes between CD and examined alcohols. By using a similar approach, we showed EPR spectroscopy can be considered a rapid and accurate technique to investigate the CDs binding behavior toward different nonradical guest.

Effects of alcohols on CE enantioseparation of basic drugs with native γ‐CD as chiral selector

The effects of alcohol on the CE enantioseparation of selected basic drugs with gamma-CD as the chiral selector was investigated. The enantioseparation behavior of the analytes with gamma-CD in the absence and presence of different alcohols specifically methanol, ethanol, 2-propanol (IPA), and 2-methyl-2-propanol (TBA), the relationship of enantiomeric resolution (R(s)) values with either hydrophobicity or bulkiness of the alcohols, as well as the effect of these alcohols on interaction of the analytes with gamma-CD were studied. Results showed that hydrophobicity and/or bulkiness of alcohols have an influence on the enantioresolution of most of the analytes based on the relatively high correlation coefficients (R) obtained between R(s) versus log P and between R(s) versus ovality (i.e., parameter to indicate bulkiness of a molecule). Comparison of the values of the average binding constants obtained for each enantiomeric pair in the presence and absence of 5% IPA showed that alcohols can increase, decrease, or give a minimal effect on the analyte-gamma-CD interaction depending on the analyte. Furthermore, the significant enhancement in the enantioresolution of both propranolol and pindolol in the presence of either IPA or TBA led to the baseline enantioresolution of both drugs using 35 mM gamma-CD.

29Si NMR Spectroscopy Investigation of Alcoholic Phenyltrimethyl Ammonium Silicate Solutions

29Si NMR spectroscopy is a powerful tool for studies of the silicate species existing in both aqueous and non-aqueous solutions. In this report 29Si NMR spectroscopy was used to characterize species present in alkaline alcoholic silicate solutions. Phenyltrimethylammonium (PTMA) hydroxide was used as a base. The effects of polymerization/depolymerization of silicate anions in alcoholic alkaline solutions were investigated with different alcohols by 29Si NMR spectroscopy. The esterification of monomeric silicate, Si(OH)4, in the presence of different alcohols was also studied. Esterification depends on the alkyl chain as well as number of hydroxyl groups in the alcohol.