Linear Alkyl Research Articles

Mechanistic elucidation of the oral pungency of capsaicin-related dietary components: Spatial structural insights

The mechanistic insights into the oral pungency of capsaicin-related dietary components have been elucidated from the spatial structural perspectives by establishing statistically significant and highly predictive three-dimensional quantitative structure–property relationship models. Our results visualized the possible favorable and unfavorable steric and electrostatic interactions with the pungent receptors with the assistance of pharmacophore models, and revealed the suitable electronegative/positive or bulky substitutions in the vanillyl group, amide moiety, linear alkyl chain and their adjacent structural area of capsaicin required for the desired pungency, which was not only complementary to the viewpoints proposed in our previous structure-pungency correlations, but also was applied to clearly clarify the pungent differences in compounds, and well predict the pungency of 21 capsaicin analogs though with ambiguous experimental data on pungency. Hopefully, this work would benefit the overall understanding of the pungent mechanism and facile discovery/design of analogs with desired pungency to expand their applications in foods.

A spectrometric approach to measuring the Rayleigh scattering length for liquid scintillator detectors

Good optical transparency is a fundamental requirement of liquid scintillator (LS) detectors. Characterizing the transparency of a liquid scintillator to its own emitted light is a key parameter to determine the overall sensitivity of a large-volume detector. The attenuation of light in an optical-pure LS is dominated by Rayleigh scattering, which poses an intrinsic limit to the transparency of LS. This work presents a spectrometric approach of measuring the wavelength-dependent scattering length of liquids by applying the Einstein-Smoluchowski theory to a measurement of scattered light intensity. The scattering lengths of linear alkyl benzene (LAB) and EJ309-base (Di-isopropylnaphthalene, DIN) were measured and are reported in the wavelength range of 410–520 nm. The spectral peak of scintillation light emitted by a nominal LS is around 430 nm at which the scattering lengths for LAB and EJ-309-base were determined to be 27.9 ± 2.3 m and 6.1 ± 0.6 m.

Synthesis, Radiosynthesis, and in vitro Studies on Novel Hypoxia PET Tracers Incorporating [18F]FDR

AbstractWe report the synthesis of five radiotracers incorporating different oxyamine spacers between the hypoxia‐reactive 2‐nitroimidazole moiety and the 5‐[18F]‐fluorodeoxyribose ([18F]FDR, 12) prosthetic group: three linear alkyl chains with 3, 5, 7 carbon atoms (15 a–c), a cyclopropyl ring (15 d) and a 1,4‐disubstituted‐1,2,3‐triazole (15 e). Experiments in hypoxic cells showed that 15 d displays superior uptake kinetics – and similar selectivity for hypoxic cells – relative to the gold standard hypoxia tracers [18F]fluoroazomycin arabinoside ([18F]FAZA) and [18F]fluoromisonidazole ([18F]FMISO). Lipophilicity and structural rigidity have strong influence on the selectivity of tracers 15 towards hypoxic cells: the lead tracer 15 d displays a logP=0.38 and the most rigid spacer. A sixth radiotracer (15 f), with a 2‐H‐imidazole replacing the 2‐nitroimidazole moiety of 15 d, was used to demonstrate that the cyclopropyl group does not play a meaningful role in the sensitivity towards hypoxia.

Molecular Origin of Carbon–Oxygen‐Bridge Isomerization Induced Reverse Aggregation Ability in Acceptor–Donor–Acceptor Electron Acceptors for Organic Solar Cells

For bulk heterojunction organic solar cells (OSCs), controlling molecular self‐aggregation during solution processing is crucial to obtain ideally phase‐separated morphology and high device performance. Recently, fused‐ring regiochemistry, for example, carbon–oxygen (CO)‐bridge isomerization, has been found to effectively modulate the aggregation structures and photovoltaic properties of acceptor–donor–acceptor (A–D–A) small‐molecule acceptors (SMAs). Strikingly, the relative aggregation ability for the CO‐bridge isomers turns out to be reverse after simultaneous replacement of the linear alkyl side chains with branched ones and fluorination of the end groups. Herein, to understand the molecular origin of such an observation, the aggregation behaviors of three pairs of CO‐bridge isomeric SMAs in solutions are systematically investigated by atomistic molecular dynamics simulations. Because of the large side‐chain steric hindrance around the fused‐ring core, the molecular self‐aggregation for all of these SMAs is dominated by end‐group π–π stacking. Moreover, the end‐group π–π interaction is controlled by the synergistic effect of CO‐bridge isomerization, side‐chain branching, and end‐group fluorination, which are responsible for the reversal of the aggregation ability of the isomeric SMAs. This work provides the rationalization of experimental observations and is helpful for modulating the blending morphologies for high‐efficiency OSCs based on CO‐bridge SMAs.

Palladium-catalyzed enantioselective linear allylic alkylation of vinyl benzoxazinanones: An inner-sphere mechanism

Palladium-catalyzed asymmetric allylic alkylation (AAA) of vinyl benzoxazinanones has become an important strategy for the synthesis of chiral nitrogen-containing heterocycle compounds. However, the asymmetric synthesis of linear-selective products has rarely been reported. The simultaneous control of regio-, E/Z- and enantioselectivities constitutes a major challenge and inhibits the advancement of this chemistry. Herein, we present a palladium-catalyzed AAA of vinyl benzoxazinanones with α-thiocyanato ketones, affording various chiral thiocyanates characterized with high linear-, E- and stereoselectivities. The reaction has a broad substrate scope and the chiral thiocyanates can be transformed to useful heterocycles. Experimental and computational studies suggest an inner-sphere mechanism for AAA process, which results from the acidic and coordination effect of the nucleophilic substrates with palladium catalyst.

Transition-Metal-Free Reductive Cross-Coupling Employing Metabisulfite as a Connector: General Construction of Alkyl–Alkyl Sulfones

Transition-Metal-Free Reductive Cross-Coupling Employing Metabisulfite as a Connector: General Construction of Alkyl–Alkyl Sulfones

Ascorbate-dependent and ascorbate-independent Mn porphyrin cytotoxicity: anticancer activity of Mn porphyrin-based SOD mimics through ascorbate-dependent and -independent routes

ABSTRACT Objective The aim of this study was to investigate how modifications at the periphery of the porphyrin ring affect the anticancer activity of Mn porphyrins (MnPs)-based SOD mimics. Methods Six compounds: MnTE-2-PyP with a short ethyl chain on the pyridyl ring; MnTnHexOE-2-PyP and MnTnOct-2-PyP with linear 8-atom alkyl chains, but the former with an oxygen atom within the alkyl chain; MnTE-2-PyPhP and MnTPhE-2-PyP with pyridyl and phenyl substituents, were investigated. Cytotoxicity was studied using pII and MDA-MB-231 cancer cell lines. Viability was assessed by the MTT (3-[4,5-dimethylthiazol-2-yl)]-2,5-diphenyltetrazolium bromide) assay and cell proliferation was determined by the sulforhodamine B assay. Results Cellular uptake was increased with the increase of the lipophilicity of the compounds, whereas reduction potential (E ½) of the Mn(III)/Mn(II) redox couple shifted away from the optimal value for efficient redox cycling with ascorbate, necessary for ROS production. Amphiphilic MnPs, however, exerted anticancer activity by a mechanism not involving ROS. Conclusion Two different processes account for MnPs cytotoxicity. MnPs with appropriate E ½ act via a ROS-dependent mechanism. Amphiphilic MnPs with suitable structure damage sensitive cellular constituents, leading to the suppression of proliferation and loss of viability. Design of compounds interacting directly with sensitive cellular targets is highly promising in the development of anticancer drugs with high selectivity and specificity.

Synthesis of Branched Copolymers of Poly(1-hexene-co-maleic anhydride)

Poly(1-hexene-co-maleic anhydride) was synthesized by addition polymerization of 1:1 of 1-hexene and maleic anhydride using 1% benzoyl peroxide as initiator. The copolymer has been branched by different lengths of linear alkyl groups (C11-C22) via melt process esterification reaction with aliphatic alcohols using 1% para toluene sulfonic acid as catalyst. The prepared copolymers were purified and characterized by FTIR and NMR spectroscopy. All analyses indicate ring-opening reaction of anhydride group constituted backbone chains with aliphatic alcohols, which confirm the validity of the proposed chemical structures of copolymers. Molecular weight determination was confirmed by GPC and end group analysis (ASTM D1386-98) and found that 1-hexene monomer constitutes the largest portion in poly(1-hexene-co-maleic anhydride) backbone.

Mechanistic study of the cooperative palladium/Lewis acid-catalyzed transfer hydrocyanation reaction: the origin of the regioselectivity.

Density functional theory (DFT) calculations have been performed to gain insights into the catalytic mechanism of the palladium/Lewis acid-catalyzed transfer hydrocyanation of terminal alkenes to reach the linear alkyl nitrile with excellent anti-Markovnikov selectivity. The study reveals that the whole catalysis can be characterized via three stages: (i) oxidative addition generates the π-allyl complex IM2, followed by β-hydride elimination leading to the intermediate IM4, (ii) ligand exchange followed by Pd-H migratory alkene insertion gives the anti-Markovnikov intermediate IM6 and (iii) IM6 undergoes a reductive elimination step to form the linear terminal nitrile 3a and regenerates the active species for the next catalytic cycle. Each stage is kinetically and thermodynamically feasible. The oxidative addition step, with a barrier of 30.9 kcal mol-1, should be the rate-determining step (RDS) in the whole catalysis, which agrees with the experimental high temperature of 110 °C. Furthermore, the origin of the high regioselectivity of the product with excellent anti-Markovnikov selectivity is discussed.

Effect of tail branching on the phase behavior and the rheological properties of amine oxide/ethoxysulfate surfactant mixtures

The formulation of highly concentrated products with low viscosity is a key issue of the surfactants industry, for both economic and ecological reasons. The rational design of surfactant tails bearing a limited number of short side chains has been proposed as a suitable strategy to meet this demand, with negligible effects on biodegradability.In this work, we investigate a mixed surfactant system, in which the branched surfactant N,N-dimethyl-2-propylheptan-1-amine oxide (C10DAO-branched) is combined with a linear alkyl ethoxysulfate one (AES). For comparison, we also study the mixtures in which the branched amine oxide is replaced by its linear isomer (C10DAO-linear).The phase behavior of this surfactant mixture in water is investigated across the entire composition range by polarized optical microscopy and small angle X-ray scattering. Moreover, the shear viscosities and viscoelastic moduli of representative samples are determined by rheological measurements.C10DAO-branched/AES aqueous mixtures form isotropic micellar solution and lamellar structures. Low viscosity was found for all these mixtures, including the most concentrated ones. In contrast, in C10DAO-linear/AES mixtures an extended hexagonal phase is detected, which presents a high viscosity. These results demonstrate tail branching and mixed aggregation to synergistically contribute to the design of high-concentration low-viscosity surfactant mixtures.

Crystallinity dictates the selection of fullerene or non-fullerene acceptors in a small molecule organic solar cell

The side chains of a molecule affect the molecular packing and crystallinity which are crucial factors determining the photovoltaic properties in organic solar cells (OSCs). In this work, two small molecule donors, BDT(X1) and BDT(X2), with identical backbone and slightly different side chains on the end groups have been designed and synthesized. Compared with BDT(X1) with linear alkyl chain, BDT(X2) featuring a branched alkyl chain in the terminal groups has larger steric hindrance and exhibits weaker crystallinity and less compact molecule stacking. Application of the two small molecule donors in OSCs shows that BDT(X1) is more suitable for IDIC, a non-fullerene acceptor, while BDT(X2) demonstrates higher OSC performance when blended with fullerene acceptor PC71BM. Morphology and grazing-incidence wide-angle X-ray scattering (GIWAXS) studies reveal that crystallinity plays a key role in determining the molecular packing and phase separation with fullerene/non-fullerene acceptors which in turn influence the charge transport and photovoltaic properties. Our results provide some guidance on selection of acceptors for a given donor and demonstrate the importance of fine tuning of the crystallinity in small molecule OSCs.

Boundary Friction of ZDDP Tribofilms

The frictional properties of ZDDP tribofilms at low entrainment speeds in boundary lubrication conditions have been studied in both rolling/sliding and pure sliding contacts. It has been found that the boundary friction coefficients of these tribofilms depend on the alkyl structure of the ZDDPs. For primary ZDDPs, those with linear alkyl chains give lower friction those with branched alkyl chain ZDDPs, and a cyclohexylmethyl-based ZDDP gives markedly higher friction than non-cyclic ones. Depending on alkyl structure, boundary friction coefficient in rolling-sliding conditions can range from 0.09 to 0.14. These differences persist over long duration tests lasting up to 120 h. For secondary ZDDPs, boundary friction appears to depend less strongly on alkyl structure and in rolling-sliding conditions stabilises at ca 0.115 for the three ZDDPs studied. Experiments in which the ZDDP-containing lubricant is changed after tribofilm formation by a different ZDDP solution or a base oil indicate that the characteristic friction of the initial ZDDP tribofilm is lost almost as soon as rubbing commences in the new lubricant. The boundary friction rapidly stabilises at the characteristic boundary friction of the replacement ZDDP, or in the case of base oil, a value of ca 0.115 which is believed to represent the shear strength of the bare polyphosphate surface. The single exception is when a solution containing a cyclohexylethyl-based ZDDP is replaced by base oil, where the boundary friction coefficient remains at the high value characteristic of this ZDDP despite the fact that rubbing in base oil removes about 20 nm of the tribofilm. XPS analysis of the residual tribofilm reveals that this originates from presence of a considerable proportion of C-O bonds at the exposed tribofilm surface, indicating that not all of the alkoxy groups are lost from the polyphosphate during tribofilm formation. Very slow speed rubbing tests at low temperature show that the ZDDP solutions give boundary friction values that vary with alkyl group structure in a similar fashion to rolling-sliding MTM tests. These variations in friction occur immediately on rubbing, before any measurable tribofilm can develop. This study suggest that ZDDPs control boundary friction by adsorbing on rubbing steel or tribofilm surfaces in a fashion similar to organic friction modifiers. However it is believed that, for primary ZDDPs, residual alkoxy groups still chemically bonded to the phosphorus atoms of newly-formed polyphosphate/phosphate tribofilm may also contribute to boundary friction. This understanding will contribute to the design of low friction, fuel efficient crankcase engine oils.Graphical

Elongation of the side chain by linear alkyl groups increases the potency of salacinol, a potent α-glucosidase inhibitor from the Ayurvedic traditional medicine “Salacia,” against human intestinal maltase

Four chain-extended analogs (12a–12d) and two related de-O-sulfonated analogs (13a and 13c) by introducing alkyl groups (a: R = C3H7, b R = C6H13, c: R = C8H17, d: R = C10H21) to the side chains of salacinol (1), a natural α-glucosidase inhibitor from Ayurvedic traditional medicine “Salacia”, were synthesized. The α-glucosidase inhibitory activities of all the synthesized analogs were evaluated in vitro. Against human intestinal maltase, the inhibitory activities of 12a and 13a with seven-carbon side chain were equal to that of 1. In contrast, analogs (12b–12d, and 13c) exhibited higher level of inhibitory activity against the same enzyme than 1 and had equal or higher potency than those of the clinically used anti-diabetics, voglibose, acarbose, and miglitol. Thus, elongation of the side chains of 1 was effective for specifically increasing the inhibitory activity against human intestinal maltase.

Effect of Different Ionic Surfactants on the Structural, Photophysical, and Morphological Properties of Water‐Based P3HT:PCBM Nanoparticle Dispersions and Films

AbstractAqueous suspensions of composite nanoparticles of poly(3‐hexylthiophene) (P3HT) and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) are fabricated by miniemulsion method using three different ionic surfactants. The aim is to study how the length and conformation of the surfactants alkyl chains affect the properties of the nanoparticles. While the morphology and dimensions of the nanoparticles are similar, UV–vis spectroscopy evidences that the internal aggregation and ordering of the P3HT chains varies within the three nanoparticle formulations. The surfactant with branched alkyl chains promote the highest degree of ordering of P3HT chains in the nanoparticles (leading to increased conjugation length). In contrast, the lowest ordering is found for the nanoparticles with the surfactant having the shortest linear alkyl chain. The optical/structural properties of nanoparticles are partially retained in the films. Besides, the surfactant with branched alkyl chains favors the strongest coalescence of nanoparticles in the thin film, promoting a further ordering of the polymeric chains in the most external shell of the nanoparticles as evidenced by steady‐state and time‐resolved UV–vis spectroscopy and confocal fluorescence microscopy. These findings might guide the engineering of new surfactants for composite nanoparticles for optoelectronic applications.

Molecular Thermodynamics for Aggregation of Surfactants with Alkylbenzene or Branched Alkane Tails: An Experimental-Modeling Approach

This work presents a molecular thermodynamic approach in which microemulsion properties are obtained by minimizing the total Gibbs energy of the system. Notably, this optimization process is carried out mainly based on the surfactant molecular structure and the solution conditions. Even though molecular thermodynamic modeling has been widely applied to oil-in-water (O/W) microemulsions, just a few studies are reported on water-in-oil (W/O) microemulsions mainly focused on ionic surfactants with linear alkyl tails. Here, we investigate the self-aggregation of different non-ionic surfactants with more complex structures acting as hydrophobic tails. In this context, we model the phase behavior of alkylphenol ethoxylate surfactant systems incorporating liquid-vapor and liquid-liquid data of alkylbenzenes from the literature. As a result, we can optimize the model parameters and describe the equilibrium micelle structure. The particle swarm optimization method was applied to minimize the Gibbs free energy for both O/W and W/O microemulsions. In order to evaluate the predictive performance of the model, we compared the experimental data with the computed critical micelle concentration and micelle size.

Effect of Covalent Surface Functionalization of Si on the Activity of Trifluoromethanesulfonic Anhydride for Suppressing Surface Recombination.

An examination of the efficacy of combining physisorbed and chemisorbed passivation strategies on crystalline Si has been performed. This report compares the influence of a linear alkyl adsorbate tethered by either a Si-C or Si-Si linkage, prepared by reaction of Si(111) with organometallic Grignard reagents or organosilanes, respectively. These modified surfaces are first analyzed and compared by IR and X-ray photoelectron spectroscopies. Their behavior toward a known potent physisorbate, trifluoromethanesulfonic anhydride (Tf2O), is then examined. Microwave photoconductivity measurements were obtained which indicate that, while Tf2O shows a beneficial lowering of surface recombination on both surface types initially, only surfaces featuring Si-C linkages exhibit long-lasting suppressed surface recombination. The data for Grignard-treated Si after exposure to Tf2O in fact represent the longest known report of surface recombination suppression by a physisorbate. Conversely, the data for the Si surfaces prepared by dehydrogenative coupling suggest that these passivating groups themselves introduce defect states that cannot be ameliorated by Tf2O physisorption.

Stable and Size Tunable CsPbBr3 Nanocrystals Synthesized with Oleylphosphonic Acid.

We employed oleylphosphonic acid (OLPA) for the synthesis of CsPbBr3 nanocrystals (NCs). Compared to phosphonic acids with linear alkyl chains, OLPA features a higher solubility in apolar solvents, allowing us to work at lower synthesis temperatures (100 °C), which in turn offer a good control over the NCs size. This can be reduced down to 5.0 nm, giving access to the strong quantum confinement regime. OLPA-based NCs form stable colloidal solutions at very low concentrations (∼1 nM), even when exposed to air. Such stability stems from the high solubility of OLPA in apolar solvents, which enables these molecules to reversibly bind/unbind to/from the NCs, preventing the NCs aggregation/precipitation. Small NCs feature efficient, blue-shifted emission and an ultraslow emission kinetics at cryogenic temperature, in striking difference to the fast decay of larger particles, suggesting that size-related exciton structure and/or trapping-detrapping dynamics determine the thermal equilibrium between coexisting radiative processes.

Olfactory and behavioral responses to acetate esters in red imported fire ant, Solenopsis invicta.

The red imported fire ant, Solenopsis invicta Buren, is one of the most successful invasive ants in the world. Previous studies indicated that benzyl acetate and prenyl acetate elicited significant electroantennography (EAG) response in S. invicta and exhibited as attractants at certain concentrations. In addition, the easy commercial availability, low cost, and low mammalian toxicity make acetate esters ideal candidates to screen for potential use in S. invicta control. We examined the EAG and behavioral responses to 26 acetate esters in all castes of S. invicta. Our results demonstrated a large diversity of EAG tuning and behavioral responses to acetate esters in S. invicta. For linear alkyl acetate esters, EAG response was clearly affected by the carbon chain length of the alkyl group. Linear alkyl acetates with five to seven carbon chain length of the alkyl group elicited significant EAG response in S. invicta, whereas those with shorter (C1 to C4) or longer (C8 to C12) carbon chain lengths did not. Different substitutions also exhibited large variety of EAG and behavioral responses in S. invicta. Our works explored the olfactory and behavioral response of S. invicta to structurally different acetate esters, and identified two potential fire ant attractants, pentyl acetate and tran-2-hexenyl acetate, and two potential repellents, hexyl acetate and cis-3-hexenyl acetate. These compounds may be useful in developing new products for fire ant management. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

Investigation of Viton O-Ring Performance for the SABRE Dark Matter Experiment

Viton O-rings will be used for critical seals of the liquid scintillator veto detector for the sodium iodide with active background rejection dark matter experiment in Australia. In this study, the combined effects of elevated temperature plus exposure to air and linear alkyl benzene (LAB) on the physical and chemical properties of Viton O-rings were investigated over time using compression set measurements and Young’s modulus tests, ATR-FTIR spectroscopy and the analysis of solvent-induced swelling. The measurements show the degradation of physical and mechanical properties of the Viton O-rings was found to be more pronounced under compression set conditions in air for the same temperature compared to LAB at the same temperatures. The ATR-FTIR results show that the effects of LAB on the surface composition of the Viton O-rings were not significant. According to solvent swelling analysis over time, the Viton O-rings are suitable for use with LAB as there were no obvious physical and chemical property degradations at three different ageing temperatures (22, 35 and 55 oC). Furthermore, the overall conclusion is that the O-rings can be expected to function efficiently for much longer than the expected operating life of the SABRE experiment.

Bioinspired surfaces with strong water adhesion from electrodeposited poly(thieno[3,4-b]thiophene) with various branched alkyl chains

In this original work, we wanted to prepare surfaces with both high hydrophobicity and strong water adhesion, as observed on rose petals or gecko foot. The surfaces are prepared by electropolymerization and using thieno[3,4-b]thiophene monomers with various branched alkyl chains. Here, branched alkyl chains are used to their lower hydrophobic properties compared to linear alkyl chains and fluorinated chains. It is observed a change from structured to smooth when the branched alkyl chain length increases. Using short branched alkyl chains, the surfaces are mainly composed of wrinkles and nanoparticles displaying high hydrophobicity ( $${\theta }_{\mathrm{w}}$$ up to 134.9°) combined with strong water adhesion, as observed on rose petals even if $${\theta }_{\mathrm{w}}$$ is less important. Dynamic contact angle measurements show that their water adhesion is extremely strong and water droplets remain stuck on them. By adding H2O in the solvent (CH2Cl2 + H2O), it is possible to release gas bubbles (H2 and/or O2) in-situ leading to more porous surfaces but here it is observed an increase of surface hydrophilicity. These original polymer surfaces have potential applications in water harvesting systems or oil/water separation membranes, for example.