Double Bond Research Articles

Preparation and characterization of hydrophobic waterborne polyurethane self‐matting coating

AbstractA green method to synthesize self‐matting waterborne polyurethane acrylic hybrid emulsion with hydrophobic function is introduced in this study. A reactive waterborne polyurethane (RWPU) dispersion containing unsaturated CC double bonds was prepared from epoxidized soybean oil. Subsequently, the RWPU dispersion was copolymerized with fluorinated monomers of different carbon chain lengths to prepare polyurethane acrylic hybrid emulsion (PUF). The results revealed the gloss levels of PUF films to be as low as 12.4 gloss units at 60°. The morphology of PUF films was observed by scanning electron microscope and three‐dimensional surface profilometer, and the relationship between surface roughness and gloss was discussed in detail. In addition, thermal gravimetric analysis was conducted to determine the thermal stability of the PUF films, and the results denoted that these PUF films exhibited excellent thermal stability. Comprehensive performance tests indicated that the RWPU dispersion, which was copolymerized with hexafluorobutyl methacrylate at a weight of 10%, exhibited a low gloss, a high contact angle of 120°, and a high elongation percentage of 423%. Furthermore, the dynamic light scattering results showed small average particle size, revealing the excellent storage stabilities.

A Simple and Promising Prediction Model to Analyze the Optical Properties of Organic Photovoltaic Materials

Optimizing light utilization is crucial in organic photovoltaics. Understanding the intricate connection between the optical properties and the chemical structure of organic materials is pivotal yet challenging in this regard. Herein, over 2800 published reports with a database of ≈300 organic non‐fullerene acceptors (NFAs) are surveyed and a mathematical model suitable for predicting and analyzing the optical properties of organic photovoltaic materials is established. The model is used to predict the optical properties of representative NFAs within experimental error, including four newly synthesized organic materials to validate the model. In addition, the reliability and applicability of the model through data transformation are demonstrated and it is found that the addition of double bonds and asymmetry in the chemical structure does not necessarily reduce the optical bandgap of organic materials. Based on the model, the strong noncovalent interaction is more significant than the weak noncovalent interaction and asymmetry on the reduction of the bandgap, which provides new insights into the design and development of organic photovoltaic materials with tunable optical properties.

Synthesis of Styrylbenzazole Photoswitches and Evaluation of their Photochemical Properties.

Styrylbenzazoles form a promising yet under-represented class of photoswitches that can perform a light-driven E-Z isomerization of the central alkene double bond without undergoing irreversible photocyclization, typical of the parent stilbene. In this work, we report the synthesis and photochemical study of 23 styrylbenzazole photoswitches. Their thermal stabilities, quantum yields, maximum absorption wavelengths and photostationary state (PSS) distributions can be tuned by changing the benzazole heterocycle and the substitution pattern on the aryl ring. In particular, we found that push-pull systems show large redshifts of the maximum absorption wavelengths and the highest quantum yields, whereas ortho-substituted styrylbenzazole photoswitches exhibit the most favorable PSS ratios. Taking advantage of both design principles, we produced 2,6-dimethyl-4-(dimethylamino)-styrylbenzothiazole, a thermally stable and efficient P-type photoswitch which displays negative photochromism upon irradiation with visible light up to 470 nm to obtain a near-quantitative isomerization with a very high quantum yield of 59%. Furthermore, 4-hydroxystyrylbenzothiazole was demonstrated to be a pH-sensitive switch which exhibits a 100 nm redshift upon deprotonation. Ortho-methylation of this switch improved the obtained PSS ratio in its deprotonated state from E:Z=53:47 to E:Z=18:82. We anticipate that this relatively unexplored class of photoswitches will form a valuable expansion of the current family of photoswitches.

A Review of Chemical Modification of Vegetable Oils and Their Applications

In order to cope with the shortage of non-renewable energy and the increasingly environmental pollution, sustainable vegetable oils, as competitive alternatives, have widely been held in the good graces of the researchers. Vegetable oils are suitable for a wide range of applications such as biofuels and biodiesel. However, the development of vegetable oils is limited due to the characteristics of unsatisfactory oxidation stability and poor cold-flow properties. Chemical modification is considered as an effective solution to enhance the performance. The research progress of the chemical modification methods and applications of vegetable oils in recent years are summarized in this review. Reducing the content of carbon–carbon double bonds and increasing the degree of saturation are the keys to improve the physicochemical properties of vegetable oils. The prospects for the development direction and challenges of vegetable oils are proposed. Future research may focus on the use of multifunctional catalysts to optimize reaction conditions or to introduce active groups with lubricating properties in epoxidation reactions and explore the combination of chemical and auxiliary methods.

Mechanism of targeted adsorption and specific action of bone char on ionic organic pollutants: An analysis based on differences in physicochemical properties

Adsorption is a widely recognized and effective method for treating high-concentration organic industrial wastewater. Bone char (BC) is a promising adsorbent for removing ionic organic pollutants (IOPs) from printing and dyeing wastewater due to its advantageous adsorption properties. To analyze BC's targeted adsorption and specific action mechanism on IOPs, the author first elucidated the physicochemical properties of BC under different preparation conditions. Subsequently, the study compared the targeted adsorption efficacy of BC on various types and molecular structures of IOPs. Through correlation analysis, feature importance analysis, and consideration of the properties of the target substance, the study investigated the targeted adsorption laws of BC for IOPs. Lastly, for substances with specific adsorption characteristics, range analysis, structure–activity relationship analysis, and quantitative analysis of adsorption mechanisms were employed to elucidate the action mechanism of BC. The results indicate that the differences in physicochemical properties (especially CEC and pH) caused by the inorganic mineral components of BC and the number of conjugated double bonds in the molecular structure of IOPs are key factors determining the adsorption effect. Controlling BC's pore structure and electrical conductivity based on the aggregates' conjugated double bonds and particle size can improve adsorption outcomes. The hierarchy of preparation factors influencing the adsorption performance of BC is pyrolysis temperature > particle size > pyrolysis atmosphere. The adsorption of malachite green (MG) by BC primarily involves chemical reactions, including mineral complexation effect (52.38 %), electrostatic interaction (24.76 %), π-π interaction (8.15 %), metal ion exchange (8.12 %), and physical pore filling (6.59 %). It is speculated that the primary interaction mechanism between BC and MG is through cation-π bonds formed between metal cations dissociated from the inorganic mineral components of BC and MG, facilitated by strong electrostatic interaction. The findings offer a theoretical basis for the practical utilization of BC in adsorbing IOPs.

2,3-Epoxyamide-alcohols in Domino Reactions: En Route to Molecular Diversity.

The synthesis of polycyclic γ- and δ-lactams bearing up to four contiguous fully controlled stereocenters is presented. For that purpose, we developed an original approach based on the use of 2,3-epoxyamides in domino reactions by taking advantage of the nucleophilic nitrogen atom and electrophilic epoxide. In reaction with enol ethers bearing gem bis-electrophiles on the double bond as Michael acceptors, four different reaction pathways were observed. They all started with a domino oxa-Michael/aza-Michael/epoxide opening sequence and depending on substrates engaged could be followed either by a lactonization or a hemiketalization/retro-aldol cascade. Thus, four original fully-substituted piperidine- or pyrrolidine-2-one scaffolds were selectively synthesized in good to high yields. Moreover, these polycyclic lactams were obtained in high stereo- and chemo-selectively highlighting the efficiency and molecular diversity offered by this new methodology that should offer various synthetic opportunities in the future.

Crystal structure of Staphylococcus aureus lipase complex with unsaturated petroselinic acid.

Staphylococcus aureus produces large amounts of toxins and virulence factors. In patients with underlying diseases or compromised immune systems, this bacterium can lead to severe infections and potentially death. In this study, the crystal structure of the complex of S. aureus lipase (SAL), which is involved in the growth of this bacterium, with petroselinic acid (PSA), an inhibitor of unsaturated fatty acids, was determined by X-ray crystallography. Recently, PSA was shown to inhibit S. aureus biofilm formation and the enzymatic activity of SAL. To further characterize the inhibitory mechanism, we determined the half-inhibitory concentration of SAL by PSA and the crystal structure of the complex. The IC50 of the inhibitory effect of PSA on SAL was 3.4 μm. SAL and PSA inhibitors were co-crystallized, and diffraction data sets were collected to 2.19 Å resolution at SPring-8 to determine the crystal structure and elucidate the detailed structural interactions. The results show that the fatty acid moiety of PSA is tightly bound to a hydrophobic pocket extending in two directions around the catalytic residue Ser116. Ser116 was also covalently bonded to the carbon of the unsaturated fatty acid moiety, and an oxyanion hole in SAL stabilized the electrons of the double bond. The difference in inhibitory activity between PSA and ester compounds revealed a structure-activity relationship between SAL and PSA. Additional research is required to further characterize the clinical potential of PSA.

Computational investigation of cis-1,4-polyisoprene binding to the latex-clearing protein LcpK30.

Latex clearing proteins (Lcps) catalyze the oxidative cleavage of the C = C bonds in cis-1,4-polyisoprene (natural rubber), producing oligomeric compounds that can be repurposed to other materials. The active catalytic site of Lcps is buried inside the protein structure, thus raising the question of how the large hydrophobic rubber chains can access the catalytic center. To improve our understanding of hydrophobic polymeric substrate binding to Lcps and subsequent catalysis, we investigated the interaction of a substrate model containing ten carbon-carbon double bonds with the structurally characterized LcpK30, using multiple computational tools. Prediction of the putative tunnels and cavities in the LcpK30 structure, using CAVER-Pymol plugin 3.0.3, fpocket and Molecular Dynamic (MD) simulations provided valuable insights on how substrate enters from the surface to the buried active site. Two dominant tunnels were discovered that provided feasible routes for substrate binding, and the presence of two hydrophobic pockets was predicted near the heme cofactor. The larger of these pockets is likely to accommodate the substrate and to determine the size distribution of the oligomers. Protein-ligand docking was carried out using GOLD software to predict the conformations and interactions of the substrate within the protein active site. Deeper insight into the protein-substrate interactions, including close-contacts, binding energies and potential cleavage sites in the cis-1,4-polyisoprene, were obtained from MD simulations. Our findings provide further justification that the protein-substrate complexation in LcpK30 is mainly driven by the hydrophobic interactions accompanied by mutual conformational changes of both molecules. Two potential binding modes were identified, with the substrate in either extended or folded conformations. Whilst binding in the extended conformation was most favorable, the folded conformation suggested a preference for cleavage of a central double bond, leading to a preference for oligomers with 5 to 6 C = C bonds. The results provide insight into further enzyme engineering studies to improve catalytic activity and diversify the substrate and product scope of Lcps.

Unraveling the Light‐Absorbing Properties of Brown Carbon at a Molecular Level

AbstractBrown carbon (BrC) exhibits a highly complex chemical composition with diverse light‐absorbing properties, which complicates our understanding of its climate impacts. This study examined the impact of molecular characteristics (including molecular mass, unsaturation, oxidation state, and polarity) and heteroatoms on the light‐absorbing properties (absorptivity and wavelength dependence) of BrC from a molecular perspective, based on the ultraviolet‐visible spectra of over 40,000 light‐absorbing substances in aerosol from different sources and ambience. Our findings reveal that the light‐absorptivity of BrC molecules increases with decreasing polarity and O/C ratio, while it rises with higher molecular mass and unsaturation. We developed predictive models for molecular absorptivity based on its double bond equivalent and O/C ratio. In addition, we observed an inverse correlation between absorptivity and wavelength dependence at the molecular level, as determined through mathematical analysis. This molecular‐level understanding provides valuable insights into BrC absorbing mechanisms, facilitating more accurate characterization in atmospheric models.

Carboxylation of Alkenes with CO2 via Photocatalytic Cleavage of C=C Double Bonds

Carboxylation of Alkenes with CO2 via Photocatalytic Cleavage of C=C Double Bonds

Finding the Ajoene Sweet-Spot: Structure-Activity Relations that Govern its Blood Stability and Cancer Cytotoxicity.

Ajoene is an organosulfur compound found in crushed garlic that exerts its anti-cancer activity by S-thiolating cysteine residues on proteins. Its development is hampered due to limited bioavailability, so in this study, we synthesised analogues of ajoene to probe the significance of the ajoene vinyl disulfide/sulfoxide core with respect to cytotoxicity and blood stability. Polar side groups were also incorporated to improve aqueous solubility. It was found that derivatives containing a vinyl disulfide functional group (4-7, as in ajoene), were more cytotoxic compared to analogues in which the double bond was removed, although the latter showed superior blood stability. It was also found that the allyl-S sulfur of the disulfide was more electrophilic to S-thiolysis based on the global electrophilicity index (ω) and the condensed electrophilic Fukui function . S-Thiolysis was found to be exergonic for the vinyl disulfides based on entropy and enthalpy computations with a deprotonated thiolate. Derivatisation to the dihydro (10, 12) and deoxydihydroajoenes (9, 11) produced analogues that were slightly less potent but with greatly improved blood stability. Taken together, the deoxydihydroajoenes present themselves as good candidates for further therapeutic development.

Conformational Analysis of (+)-Germacrene D-4-ol Using the Crystalline Sponge Method to Elucidate the Origin of its Instability.

Unsaturated cyclic terpenes often exhibit instability due to the proximation of C=C bonds in the cyclic skeleton, leading to nonenzymatic degradation. In this study, the crystalline sponge (CS) method was employed for the X-ray conformational analysis of a minute amount of oily and cyclic terpene compound, (+)-germacrene D-4-ol, which was produced by a terpene synthase OILTS under in vitro conditions. The CS method revealed a reactive conformation of the cyclic terpene with proximal double bonds. Under weakly acidic in vivo conditions, OILTS gave four pseudo-natural products or artifacts. The CS method also elucidated the structures of these degraded compounds, proposing a degradation mechanism triggered by the transannular reactions.

The Miraculous of Rhizopus arrhizus in the Structural Modifications of Steroidal Skeleton

Abstract: Many natural and synthetic steroidal compounds have been converted by biotransformation to get highly valuable products for pharmaceuticals or chemical intermediates for the production of drugs. This review summarizes the biotransformation of sixty-six steroids1-66 (ten of pregnane 1-10, fifty of androstane 11-60 while six steroids of estrane series 61-66) by using different strains of Rhizopus arrhizus, a well-known fungus of the zygomycetes group, used in food, dairy, pharmaceutical and numerous biotechnological processes. R. arrhizus transformed only fifty-four compounds 1-51 and 61-63, whereas nine compounds of androstane 52-60 and three compounds of estrane series 64-66 remained unchanged. R. arrhizus brought various structural modifications in steroids, including hydroxylation, epoxidation, epoxide hydrolysis, reduction of double bonds and ketonic group, dechlorination and defluorination, deacetylation, oxidation of various functional groups and isomerization.

One chiral fingerprint to find them all

Molecular fingerprints are indispensable tools in cheminformatics. However, stereochemistry is generally not considered, which is problematic for large molecules which are almost all chiral.Herein we report MAP4C, a chiral version of our previously reported fingerprint MAP4, which lists MinHashes computed from character strings containing the SMILES of all pairs of circular substructures up to a diameter of four bonds and the shortest topological distance between their central atoms. MAP4C includes the Cahn-Ingold-Prelog (CIP) annotation (R, S, r or s) whenever the chiral atom is the center of a circular substructure, a question mark for undefined stereocenters, and double bond cis–trans information if specified. MAP4C performs slightly better than the achiral MAP4, ECFP and AP fingerprints in non-stereoselective virtual screening benchmarks. Furthermore, MAP4C distinguishes between stereoisomers in chiral molecules from small molecule drugs to large natural products and peptides comprising thousands of diastereomers, with a degree of distinction smaller than between structural isomers and proportional to the number of chirality changes. Due to its excellent performance across diverse molecular classes and its ability to handle stereochemistry, MAP4C is recommended as a generally applicable chiral molecular fingerprint.Scientific contribution The ability of our chiral fingerprint MAP4C to handle stereoisomers from small molecules to large natural products and peptides is unprecedented and opens the way for cheminformatics to include stereochemistry as an important molecular parameter across all fields of molecular design.Graphical

Anti-inflammatory lindenane sesquiterpenoid dimers from the roots of Chloranthus holostegius var. trichoneurus.

Two new lindenane-type sesquiterpenoid dimers, chlotrichenes C and D (1 and 2) together with five known lindenane-type sesquiterpenoid dimers (3-7) were isolated from the roots of Chloranthus holostegius var. trichoneurus, a famous natural medicine named as "Sikuaiwa" for subduing swellings and relieving pain. The structures including absolute configuration were elucidated by their 1D and 2D NMR, HRESIMS, and ECD data. Compounds 1 and 2 were classical [4 + 2] lindenane-type sesquiterpenoid dimers that differed from known analogs in oxidation profile, side chain profile, and double bond position. The new isolates and compound 3 exhibited significant inhibitory activity on IL-1β production (IC50: 1-15μM) in LPS-induced THP-1 cells and other compounds exhibited inhibitory activity on NO production in LPS-induced RAW 264.7 cells (IC50: 24-33μM).

Iodine-promoted amide formation via oxidative cleavage of indoles: novel quinazoline-4(3H)-one and tryptanthrin syntheses.

A highly efficient method for the direct construction of amide bonds via a selective cleavage of C-H and C[double bond, length as m-dash]C bonds in indole structures using an iodine-promoted approach was developed. Mechanistic studies indicated the formation of superoxide radicals obtained from molecular oxygen activation as a key intermediate step, which provided a precursor for subsequent oxidative ring-opening and intermolecular cyclization. A broad range of quinazolin-4(3H)-ones and tryptanthrins were synthesized in moderate to good yields under mild and environmentally benign conditions.

Visible‐Light‐Driven Formyl Group Migration Triggered Remote Desaturation

Dehydrogenation of unactivated alkanes to form versatile alkenes is an important but challenging task in synthetic chemistry. Enabled by a radical‐mediated formyl group migration, a novel visible light‐induced remote desaturation of aldehydes is developed, delivering a panel of trifluoromethylated δ,ε‐ or γ,δ‐unsaturated aldehydes in moderate to excellent yields with good functional group tolerance at room temperature. Mechanistic studies indicate a reaction pathway comprising the cascade trifluoromethylation of C‐C double bonds, intramolecular addition to aldehydes, β‐fragmentation of alkoxy radicals, single electron transfer oxidation, and deprotonation. It provides a good complementary approach to the existing desaturation protocols.

Carbene-Stabilized Phosphagermylenylidene: A Heavier Analog of Isonitrile.

Phosphagermylenylidenes (R-P═Ge), as heavier analogs of isonitriles, whether in their free state or as complexes with a Lewis base, have not been previously identified as isolable entities. In this study, we report the synthesis of a stable monomeric phosphagermylenylidene within the coordination sphere of a Lewis base under ambient conditions. This species was synthesized by Lewis base-induced dedimerization of a cyclic phosphagermylenylidene dimer or via Me3SiCl elimination from a phosphinochlorogermylene framework. The deliberate integration of a bulky, electropositive N-heterocyclic boryl group at the phosphorus site, combined with coordination stabilization by a cyclic (alkyl)(amino)carbene at the low-valent germanium site, effectively mitigated its natural tendency toward oligomerization. Structural analyses and theoretical calculations have demonstrated that this unprecedented species features a P═Ge double bond, characterized by conventional electron-sharing π and σ bonds, complemented by lone pairs at both the phosphorus and germanium atoms. Preliminary reactivity studies show that this base-stabilized phosphagermylenylidene demonstrates facile release of ligands at the Ge atom, coordination to silver through the lone pair on P, and versatile reactivity including both (cyclo)addition and cleavage of the P═Ge double bond.

Light‐dependent Reactivity of Heavy Pnictogen Double Bonds

The chemistry of light dipnictenes has been widely investigated in the last century with remarkable achievements especially for azobenzene derivatives. In contrast, distibenes and dibismuthenes are relatively rare and show very limited reactivity. Herein, we have designed a protocol using visible light to enhance the reactivity of heavy dipnictenes. Exploiting the distinctive π‐π* transition, we have been able to isolate unique examples of dipnictene‐cobalt complexes. The reactivity of the distibene complex was further exploited using red light in the presence of a diazoolefin to access an unusual four‐membered bicyclo[1.1.0]butane analog, containing only a single carbon atom. These findings set the bases to a conceptually new strategy in heavy element double bonds chemistry where visible light is at the front seat of bond activation.

Relay catalysis over Pd-catalysts induced by two divergent ligands for cascade bis-alkoxycarbonylation of alkynes

The mono-metal relay catalysis is a good strategy for one-pot multi-step cascade process in which the specific catalysis can be switched upon the ligand exchange to match the requirements for each independent reaction but without mutual interference and quenching problem. Herein, the one-pot cascade bis-alkoxycarbonylation of terminal alkynes was achieved by taking advantages of the mono-metallic (Pd) relay catalysis, wherein the two kinds of divergent di-phosphines of L1 and DTBPMB were involved. In this Pd(OAc)2-L1-DTBPMB system, due to the steric bulkiness of L1 and DTBPMB, the two type of catalysts including Pd(OAc)2-L1 and Pd(OAc)2-DTBPMB co-existed independently and compatibly. Pd(OAc)2-L1 system was only in charge of the first-step carbonylation of alkynes towards the branched α,β-unsaturated esters with gem-positioned double bond. Subsequent, Pd(OAc)2-DTBPMB system took over the carbonylation of the branched α,β-unsaturated esters to afford the target diesters. It was indicated Pd(OAc)2-L1 system was an efficient and stable catalyst which could be recycled upon 15 runs for the first-step carbonylation. Anyway, Pd(OAc)2-DTBPMB system easily underwent deactivation, which degraded the recyclability of the Pd(OAc)2-L1-DTBPMB coupling system for this cascade bis-alkoxycarbonylation.