Influence Of Alkyl Substituents Research Articles

Comprehensive Thermodynamic Study of Alkyl-Cyclohexanes as Liquid Organic Hydrogen Carriers Motifs

Alkyl-cyclohexanes can be considered as suitable model compounds to understand the thermochemistry of aromatic compounds and their hydrogenated counterparts discussed as Liquid Organic Hydrogen Carrier systems. Thermochemical measurements on these hydrogen-rich compounds are thwarted by complications due to the 99.9 % purity limitation and sample size specific to these methods. However, the data on vaporisation and formation enthalpies are necessary to optimize the hydrogenation/dehydrogenation processes. In this work, various empirical and theoretical methods are described to reliably assess the gas phase enthalpies of formation and vaporization enthalpies of alkyl-substituted cyclohexanes. The empirical and quantum-chemical methods have been validated against reliable literature data and provide reasonable estimates with an accuracy comparable to that of the experimental data. The liquid phase enthalpies of formation of differently shaped alkyl-cyclohexanes were derived and used to estimate the energetics of their dehydrogenation reactions. The influence of alkyl substituents on the reaction enthalpy is discussed. The vapour pressures of typical hydrogen-rich compounds at technically relevant temperatures were calculated and compared to vapour pressures of biodiesel fuels measured in this work using the static method.

Influence of alkyl substituent on thermophysical properties and CO2 absorption studies of diethylenetriamine- based ionic liquids

Diethylenetriamine (DETA) based protic ionic liquids (ILs) containing different carboxylate as anions have been synthesized and characterized by using NMR, ATR-FTIR, and mass spectroscopic techniques. The alkyl chain of carboxylate anion varied from formate (For) to octanoate (Oct). The synthesized DETA based ILs were subjected to CO2 absorption studies, and the results revealed that the CO2 absorption increases with increasing alkyl chain length of anion, and maximum CO2 absorption capacity were observed for [DETA][Oct]. The CO2 absorption results were confirmed by FTIR spectroscopic studies by monitoring the carbamate peak formation at 1634 cm−1. Furthermore, the physicochemical properties such as density (ρ), polarity, speed of sound (u), viscosity (η), and refractive index (nD) were determined at different temperatures from 293.15 to 333.15 K and pressure (0.1 MPa). The thermal stability of synthesized ILs was established using TGA analysis. The derived thermodynamic properties such as thermal expansion coefficient (α), isentropic compressibility (βS), intermolecular free length (Lf), lattice potential energy (UPOT), molecular volume (V), standard entropy (S°), activation energy (En), molar refraction (Rm) and free volume (Vf) were calculated from experimental data to predict the intermolecular interactions and space between constituent ions in the ILs and it was found that [DETA][Oct] having highest CO2 absorption capacity due to its higher free volume and basicity compare to other ionic liquids.

Influence of alkyl substituents in cations of mononuclear dinitrosyliron complexes containing thiourea ligands on the mechanism of the reaction with molecular oxygen: a quantum chemical study

Influence of alkyl substituents in cations of mononuclear dinitrosyliron complexes containing thiourea ligands on the mechanism of the reaction with molecular oxygen: a quantum chemical study

Extraction of Selected Metal Ions with Mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6

ABSTRACT Previous work has shown that solvent extraction (SX) and extraction chromatography (EXC) systems containing mixtures of extractants can be utilized to impart selectivity and improved physical characteristics that were not achievable with a single extractant. In an effort to discover EXC materials with unique selectivity and improved physical properties, we studied the extraction of selected metal ions from nitric acid and hydrochloric acid by EXC resins prepared from mixtures of N,N,N’,N’-tetra-n-octyldiglycolamide (TODGA) and 4,4′(5′)-di-t-butylcyclohexano 18-crown-6 (dtBCH18C6). Except for enhanced extraction of Ra and Ba from dilute HNO3, the EXC resins essentially exhibited the metal ion extraction properties expected from materials prepared with the individual extractants. The origin of the Ra/Ba enhancement was studied by solvent extraction variation studies in 1-octanol and n-dodecane and on extraction chromatography resins, indicating that the enhancement may not be a true synergistic interaction between the extractants, but a phase modification by the TODGA related to the co-extraction of HNO3 and water. Additionally, the influence of alkyl substituents on the DGA extractant and potential applications of the mixed extractant system in analytical chemistry and nuclear medicine were explored with extraction chromatography resins prepared from the extractant mixtures.

Influence of Alkyl Substituent on Optical Properties of Carboxylate-Based Protic Ionic Liquids

The solvation strength of N,N-dialkylethanolammonium based protic ionic liquids (PILs) have been determined by normalised Reichardt's parameter (ETN ) and molecular polarizability (αP). The solvation strength depends on the intermolecular interactions which are governed by the functional group and molecular structure of the species. So here in this work, the influence of functional groups such as –OH, –RCOOH and –R, on solvatochromic parameters of studied PILs have been discussed in terms of experimental results and relevant literature. Further the intermolecular interactions of PILs have been analyzed with the help of temperature dependant experimental refractive index data. Additionally, a positive correlation was obtained between the polarity and the refractive index of the studied PILs.

Molecular Design of Carbazole-based Dyes and the Influence of Alkyl Substituent on the Performance of Dye-Sensitized Solar Cells

ABSTRACTCarbazole is an alternant polycyclic aromatic hydrocarbon consisting of three fused rings with a large, aromatic system, containing nitrogen atom showing extensive electron delocalization. In this work, carbazole applied as π-conjugated bridge to construct electron donor–π–electron acceptor (D–π–A) organic dyes, where barbutiric acid and thiazolidine-2,4-dione as electron acceptor. The effects of these three acceptors and length of alkyl on the performance of the DSSCs were investigated systematically along with their photophysical and photo electrochemical properties. These series of organic dyes include (B-CH, B-C B, DT-CB, DB-CB). Our investigation indicate among dyes containing butyl as same donor, DT-CB exhibited the maximum overall conversion efficiency of 1.44% and from dyes by deferent electron donor B-CH shows conversion efficiency of 1.47%.

Influence of alkyl substituents in 1,3-diethyl-2-thiobarbituric acid on the coordination environment in M(H2O)2(1,3-diethyl-2-thiobarbiturate)2 M = Ca2+, Sr2+

Two new isostructural complexes, [Ca(H2O)2(μ2-Detba-O,O′)2]n (1) and [Sr(H2O)2(μ2-Detba-O,O′)2]n (2) (HDetba = 1,3-diethyl-2-thiobarbituric acid), were synthesized and characterized by single-crystal and powder X-ray diffraction analysis, TG-DSC, FT-IR, and emission spectroscopy. The single-crystal X-ray diffraction data revealed that 1 and 2 are polymeric where M2+ (M = Ca, Sr) is a six-coordinate octahedral binding four Detba− ions and two water molecules. The octahedra are linked through bridging Detba− ions forming a 2-D layer. Two intermolecular hydrogen bonds O–H…S in the crystal form a 3-D net. The comparison of M(Detba)2 and M(Htba)2 (H2tba = 2-thiobarbituric acid) structures showed that the coordination number of metals in M(Detba)2 does not exceed six and there are no π–π interactions, unlike compounds with Htba−; Detba− ions are only bridges in HDetba coordination compounds. Thermal decomposition of 1 and 2 includes dehydration, which mainly ends at 200 °C, and organic ligand oxidation at 300–350 °C with a release of CO2, SO2, H2O, NH3, and isocyanate. Upon excitation at 220 nm, 1 and 2 exhibit an intense emission maximum at 557 nm.

Influence of alkyl substituents in corrphycene on geometry, electronic structure, hydrogen bonding, and tautomerization

Geometry, electronic and vibrational structure, and relative energies of different tautomeric forms have been calculated for free base corrphycene and its five tetra-, octa-, and dodeca-alkyl-substituted derivatives, of which only one has been synthesized so far. The results demonstrate that the lowest energy structure always corresponds to the transtautomeric form. Comparison with the experimental IR and X-ray data available for 2,3,6,7,11,12,17,18-octaethylcorrphycene shows, in contrast to previous suggestions, that th. transspecies is dominant both in solution and crystalline phase. Based on structural, spectral, and computational data, rates of double hydrogen transfer can be predicted. Tautomerization is expected to occur in a nanosecond or subnanosecond range. The rate should strongly decrease upon substituting parent corrphycene with alkyl groups at the pyrrolic [Formula: see text] positions, whereas the opposite effect is expected for mesosubstitution. Depending on the position of substituent, planar or nonplanar geometries of the corrphycene chromophore are predicted. The nonplanarity leads to a substantial increase of the intensity of the low energy electronic transitions (Q-bands).

Thermochemical Studies of Epoxides and Related Compounds

Gas-phase heats of formation for the four butene oxide isomers are reported. They were obtained by measuring the condensed-phase heat of reduction to the corresponding alcohol using reaction calorimetry. Heats of vaporization were determined and allow gas-phase heats of formation to be obtained. The experimental measurements are compared to calculations obtained using a variety of computational methods. Overall, the G3 and CBS-APNO methods agree quite well with the experimental data. The influence of alkyl substituents on epoxide stability is discussed. Comparisons to alkenes, cyclopropanes, aziridines, thiiranes, and phosphiranes are also made. Isodesmic-type reactions were used to determine strain energies of the epoxides and related compounds with various substituents.

Solid-Phase Synthesis of Unsymmetrical trans-Stilbenes

A small library of fluorescent and unsymmetrical trans-stilbene compounds was efficiently produced by a solid-phase synthetic approach using the sulfonate-based traceless linker system. Nickel(0)-catalyzed cleavage/cross-coupling of polymer-bound stilbenesulfonates with aryl Grignard reagents generated the desired trans-stilbenes at high yield by the multifunctional release facilitating the additional diversification of the library. The luminescent properties of trans-stilbenes are assessed, and the influence of alkyl substituents on their photophysical properties is discussed.

Simultaneous determination of enantiomerization and hydrolysis kinetic parameters of chiral N‐alkylbenzothiadiazine derivatives

On-column stopped flow multidimensional HPLC (sfMDHPLC) and dynamic high-performance liquid chromatography were applied to investigate the influence of alkyl substituents at the sulfonamidic and amino moieties of benzothiadiazine 1,1-dioxide derivatives on hydrolysis and enantiomerization rate constants. The data obtained indicate the presence of pyrrolo substituent at the 3,4 positions on benzothiadiazine rings inhibits the hydrolysis, whereas the enantiomerization occurs in acidic medium. Hydrolysis rates are quite similar for the two benzothiadiazines methyl substituted to nitrogen at 2- and 4-positions. Conversely, enantiomerization rate of 4-N-methyl substituted is significantly higher than 2-N-methyl substituted.

Influence of alkyl substituents and thermal annealing on the film morphology and performance of solution processed, diketopyrrolopyrrole-based bulk heterojunction solar cells

A solution processable diketopyrrolopyrrole-containing oligothiophene was blended with a series of methanofullerene acceptors having different alkyl substitutents—[6,6]-phenyl C61 butyric acid methyl (PC6161BM) ester, [6,6]-phenyl C61 butyric acid hexyl ester (PC6161BH) and [6,6]-phenyl C61 butyric acid dodecyl ester (PC6161BD) to study the effect of donor–acceptor interactions on the blend film morphology and device characteristics of small molecule-based bulk heterojunction (BHJ) solar cells. A combination of characterization techniques including X-ray diffraction, atomic force microscopy, conducting atomic force microscopy, and transmission electron microscopy was used to investigate the film morphology and phase separation. The results show that changing the length of the alkyl substituent on the methanofullerene acceptor is a good approach to control the film morphology of blended films and these lead to significant differences on the performance of the as cast and annealed devices. Power conversion efficiencies between 2–3% can be reached by simple variation of the alkyl chain length.

The influence of alkyl substituents on the chromatographic indicator of self-association ofN-containing heterocyclic compounds

The chromatographic indicator of the ability of substances to form associates in a pure liquid δT b.p. proposed in our previous study was used to estimate the capacity for self-association of alkyl-substituted imidazoles, pyrazoles, pyrroles, oxazoles, isoxazoles, pyridazines, pyrimidines, pyrazines, and pyridines. Alkyl substituents introduced in heterocyclic compounds decrease the δT b.p. values, which is consistent with the data on the heats of self-association of heterocyclic compounds in pure liquids. The reasons for the difference between the boiling point of a compound at standard pressure and its “gas-chromatographic boiling point” are discussed.

Influence of Alkyl Substituents on the Polymerization Behavior of Asymmetric Ethylene-Bridged Zirconocene Catalysts

A series of substituted indenyl−fluorenyl asymmetric ethylene-bridged ligands have been prepared from the reaction of 1-(9-fluorenyl)-2-bromoethane and the lithium salt of the desired indenyl moiety. The ligands have been converted to the corresponding substituted asymmetric ethylene-bridged metallocenes (M = Zr, Hf). These metallocenes have been evaluated as catalyst precursors for the polymerization of ethylene and propylene. The influence of substitution on the selectivity of the propylene polymerization has been studied. The metallocene [1-(9-fluorenyl)-2-(2,4,7-trimethyl-1-indenyl)ethane]zirconium dichloride was found to produce highly isotactic polypropylene with an [mmmm] value of 86%.

ChemInform Abstract: Influence of Alkyl Substituent on the Asynchronous Transition Structure of Boron‐Catalyzed Diels‐Alder Cycloaddition of α,. beta.‐Unsaturated Aldehydes with 1,1‐Dimethyl‐1,3‐butadiene Derivatives.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Rhodium-catalysed hydroformylation of branched 1-alkenes; bulky phosphite vs. triphenylphosphine as modifying ligand

The influence of alkyl substituents in 1-alkene substrates in the rhodium-catalysed hydroformylation in the presence of tris(2-tert-butyl-methylphenyl) phosphite has been studied and compared with that observed for the reaction involving the conventional PPh 3-modified catalyst. Hindered alkenes underwent hydroformylation at good rates (i.e. 1300 mol (mol Rh) −1 h −1 for 3,3-dimethyl-1-butene as T = 70°C and P = 20 bar (H 2CO)); under mild conditions the rates were only slightly affected by the alkyl substituents. The selectivity towards the linear aldehyde increases progressively with substitution, from 66% for 1-octene up to 100% for 3,3-dimethyl-1-butene, and the proportion of isomerized alkenes remained substantial (up to 17.4% for allylcyclohexane). The differences between the two systems are explained in terms of the different kinetics observed for them.

Influence of Alkyl Substituent on the Asynchronous Transition Structure of Boron-Catalyzed Diels-Alder Cycloaddition of .alpha.,.beta.-Unsaturated Aldehydes with 1,1-Dimethyl-1,3-butadiene Derivatives

Influence of Alkyl Substituent on the Asynchronous Transition Structure of Boron-Catalyzed Diels-Alder Cycloaddition of .alpha.,.beta.-Unsaturated Aldehydes with 1,1-Dimethyl-1,3-butadiene Derivatives

ChemInform Abstract: Self‐Association of Pyridine and Some of Its Derivatives (I)‐(VII) in Aqueous Solution: Influence of Alkyl Substituents.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Self-association of pyridine and some of its derivatives in aqueous solution: influence of alkyl substituents

Abstract The self-association of pyridine and some of its alkyl derivatives (2-, 3- and 4-picoline, 2,4- and 2,6-lutidine, 4-tert-butyl- and 2,6-di-tert-butylpyridine) was studied in aqueous solution, at different pH values, by UV spectroscopy. The variation in molar absorptivity with concentration was measured not only for the main maximum, but also for the different component bands of the adsorption band in the mid-UV region (above 200 nm) of these compounds. From the experimental curves of hypochromic effects, self-association constants for dimerization (K2) and polymerization (Kn) were calculated. The results obtained are discussed in detail with relation to the position and nature of alkyl substituents on the pyridine ring. The most relevant result is the influence of alkyl substituents on self-association, particularly the special role of the methyl substituents in ortho positions with respect to the nitrogen atom in 2-picoline, 2,4- and 2,6-lutidine. In 2-picoline and 2,6-lutidine, polymerization can be studied separately from dimerization by measuring the band at longest wavelength, which suggests a possible relationship between the mechanism of formation of polymers and the π* ← n transitions which give rise to these bands.

Quantitative analysis of solvation effects and the influence of alkyl substituents on the basicity of amines

From potentiometric titrations, the relative free energy changes for the basicities of selected alkyl-substituted dimethylamines have been determined in 11 different solvents. For all the solvents used, the size of alkyl substituents on dimethylamines plays a significant role in basicity. For each solvent, increased basicities are dictated primarily by substituent polarizability effect. The sensitivity of the basicity to a change of substituent depends largely on dipolarity/polarizability and basicity properties of solvents