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Knowledge of the density of n -nonane + cyclopentane plays an important role in the design calculation, process simulation, and quality control of fuel industry. The liquid densities of n -nonane + cyclopentane binary mixtures (x 1 = 0, 0.2010, 0.3962, 0.6049, 0.8023, and 1) were measured using a high pressure vibrating-tube densimeter at 293–363 K and pressures up to 100 MPa. The density data obtained in this work were correlated using the modified Tait equation over the entire temperature and pressure range, and the absolute average deviations of the experimental and calculated values were 0.010 %, 0.016 %, 0.009 %, 0.011 %, 0.010 %, and 0.014 %, respectively. Comparisons have also been made with the available literature and satisfactory agreement was found. Finally, the isothermal compressibility, isobaric thermal expansivity, and excess molar volume were derived from the density data. [ABSTRACT FROM AUTHOR]

Chlororaphens A and B are structurally unique non‐canonical C17 sesquiterpenoids from Pseudomonas chlororaphis that are made by two SAM‐dependent methyltransferases and a type I terpene synthase. This study addresses the mechanism of their formation in isotopic labelling experiments and DFT calculations. The results demonstrate an astonishing complexity with distribution of labellings within a cyclopentane core that is reversely connected to two acyclic fragments in chlororaphen A and B. In addition, the uptake of up to 14 deuterium atoms from D2O was observed. These findings are explainable by a repeated late stage multistep rearrangement sequence. The absolute configurations of the chlororaphens and their biosynthetic intermediates were elucidated in stereoselective labelling experiments. [ABSTRACT FROM AUTHOR]

Comprehensive Summary: A visible light photocatalytic [3+2] cycloaddition of alkynes with readily accessible organic iodides as the C3 synthon is developed herein. By merging halogen atom transfer (XAT) and hydrogen atom transfer (HAT), alkyl/aryl iodides serve as a formal diradical precursor and add across C‐C triple bonds to deliver a number of functionalized cyclopentanes in moderate to high yields with exceptional regio‐ and diastereoselectivity. A reductive radical‐polar crossover mechanism, involving the cascade XAT, radical addition, 1,5‐HAT, polar effect‐promoted 5‐endo annulation, single electron transfer (SET) reduction, and protonation, may account for this unprecedented dehalogenative [3+2] cycloaddition. This work not only expands the repertoire of the traditional RATC methodology, but also provides a robust platform for the expedient assembly of cyclopentanes, a valuable structural motif in the realms of medicinal chemistry and material sciences. [ABSTRACT FROM AUTHOR]

The helix preferences of cyclopentane-containing β/γ-hybrid oligomers, consisting of alternating βAc5a (2-aminocyclopentanecarboxylic acid) and γ(Et)Ac5a [2-(2-aminocyclopentyl)butanoic acid] residues with homochiral S-configurations, were investigated through conformational searches and density functional theory calculations in chloroform. The β/γ-hybrid dimer exhibited a distinct inclination toward a ribbon-like structure characterized by alternating C8 and C9 H-bonds. However, for β/γ-hybrid oligomers longer than tetramer, a preference for a right-handed (P)-2.413-helical structure emerged. The robust stabilities observed for the H13 helical structures in chloroform were attributed to the favored solvation free energies, which increased with the length of the peptide sequence. Calculations revealed that the mean backbone torsion angles of the H13 helix foldamer in the β/γ-hybrid pentamer closely resembled those observed in X-ray structures of the pentamer consisting of βAc5a and a γ-residue with a cyclohexane substituent. The introduction of cyclopentane substitutions led to distinct conformational preferences and/or handedness of helix foldamers compared to those of the unsubstituted β/γ-hybrid oligomers. Notably, a pyrrolidine-substituted analog of the H13 helical structure for the β/γ-hybrid pentamer, with adjacent amine diads substituted in close proximity, appears to be a promising organic catalyst for organic reactions such as the crossed aldol condensation and the cyclodimerization of dialdehyde in nonpolar solvents, as previously elucidated. [ABSTRACT FROM AUTHOR]

Diazomethane‐mediated C‐C bond cleavage of α‐keto N,O‐hemiaminals was investigated for the first time. Diazomethane as a reagent result C‐C bond cleavage of norbornyl α‐keto N,O‐hemiaminals, Grob‐like fragmentation, lead to the formation of cyclopentane annulated δ‐lactams in excellent yields. We have synthesized the precursor norbornyl α‐keto N,O‐hemiaminal by the nucleophilic displacement of halogen of norbornyl α‐diketone with the various amines. [ABSTRACT FROM AUTHOR]

We reported a chiral oxamide‐phosphine ligand (COAP−Ph)‐Pd‐catalyzed asymmetric [3+2] cycloaddition reaction between vinyl cyclopropane compounds derived from 1,3‐indanedione and 2‐vinylcyclopropane‐1,1‐dicarboxylates with cyclic sulfonyl 1‐azadienes. The corresponding reactions provided a series of enantiomerically active spiro cyclopentane‐indandione and cyclopentane structures bearing three consecutive stereogenic centers in good yields with good diastereo‐ and enantioselectivity. The COAP−Pd complex serves not only to promote generation of chiral π‐allyl‐palladium intermediates and induce the asymmetry of the reaction, but also depress the background reaction. [ABSTRACT FROM AUTHOR]

Hydrates are crystalline solids with an ice-like texture, which are formed when light hydrocarbon molecules and water combine to form a specific ordered structure. Hydrate formation begins at the water–hydrocarbon interface, which highlights the critical role that interfacial rheology plays in this process. Despite the significance of this interface in hydrate formation, a gap in research persists, particularly in employing shear rheology approaches. This study helps to fill this void by investigating the mechanical and flow properties of the interface, using a feature in a rotational rheometer, a "double wall ring cell," for precise temperature control. Cyclopentane serves as the hydrate former, allowing experimentation under atmospheric pressure and varied temperatures. Protocols explore temperature and hydrocarbon concentrations, with emphasis on ice crystal involvement in hydrate formation initiation. Following complete saturation of the hydrocarbon/water interface by hydrates, interfacial elastic and viscous moduli are obtained through strain sweeps to assess hydrate film fragility and mechanical response. Additionally, the impact of aging time and shear type (static or dynamic) on hydrate stiffness is examined. Tests with thermodynamic inhibitors, such as sodium chloride and monoethylene glycol, demonstrate significant induction time extension. Furthermore, systematic changes in the shear rate are investigated to comprehensively understand their influence on hydrate film characteristics and properties under varying shear history conditions. This study reveals that increasing shear rate correlates with decreased viscosity of the hydrate film, indicative of non-Newtonian behavior. Overall, this research sheds light on the nuanced dynamics of the water–hydrocarbon interface in hydrate formation and mitigation. [ABSTRACT FROM AUTHOR]

Freshwater scarcity is a critical issue in Vietnam, particularly in the Mekong Delta, a densely populated region with an agriculture-based economy. This scarcity is largely driven by saltwater intrusion during the dry season, severely affecting both agriculture and the local economy. In response, advanced desalination technologies have been proposed. In this study, we investigated the use of cyclopentane (CP), a liquid guest molecule, and 1,1,1,2-tetrafluoroethane (R134a), a gaseous guest molecule, as hydrate formers to desalinate saline water from the Mekong Delta. This study aimed to evaluate and compare the freshwater recovery efficiencies of these hydrate formers and assess the potential of hydrate technology for practical application in the region. We performed thermodynamic and kinetic investigations on sodium chloride solutions (1.0–3.5 wt%), representing the salinity levels of seawater in the Mekong Delta, to establish a laboratory-scale desalination system. The results showed a consistent thermodynamic trend: the higher concentration of samples leads to the longer time of hydrate formation to achieve the conversion of water into hydrates exceeding 60 %. Additionally, the CP and R134a hydrate structures were characterized using Raman spectroscopy, which revealed significant changes in the water peak and C–H band signal during the hydrate formation process. After a single-stage hydrate treatment using CP and R134a, the removal efficiencies for ions and total dissolved solids in saline water samples from the Mekong Delta exceeded 75 % and 70 %, respectively. These findings serve as a reference for developing a larger-scale hydrate-based desalination technology to address the challenges of saltwater intrusion in the Mekong Delta region.

Isatropolone C from Streptomyces sp. CPCC 204095 features a fused cyclopentadienone-tropolone-oxacyclohexadiene tricyclic moiety in its structure. Herein, we report an isatropolone C dimer derivative, di-isatropolone C, formed spontaneously from isatropolone C in methanol. Notably, the structure of di-isatropolone C resolved by NMR reveals a newly formed cyclopentane ring to associate the two isatropolone C monomers. The configurations of four chiral carbons, including a ketal one, in the cyclopentane ring are assigned using quantum NMR calculations and DP4+ probability. The plausible molecular mechanism for di-isatropolone C formation is proposed, in which complex dehydrogenative C-C bond coupling may have happened to connect the two isatropolone C monomers. Like isatropolone C, di-isatropolone C shows the biological activity of inducing autophagy in HepG2 cells. [ABSTRACT FROM AUTHOR]

Cyclopentane (C5H10) and tetrahydrofuran (C4H8O) are both five‐membered ring compounds. The present study compares the auto‐ignition of cyclopentane and tetrahydrofuran in a high‐pressure shock‐tube (20 atm). Twelve different mixtures were investigated at two different fuel initial mole fractions (1% and 2%): at Xfuel = 1%, three equivalence ratios, kept constant between cyclopentane and tetrahydrofuran, were studied (0.5, 1, and 2), whereas three Xfuel/XO2 were investigated when Xfuel = 2%. A detailed kinetic mechanism was developed to reproduce cyclopentane and tetrahydrofuran auto‐ignition. The agreement between our experimental results and the modeling is very good. This mechanism was used to explain the similarities and differences observed between cyclopentane and tetrahydrofuran auto‐ignition. [ABSTRACT FROM AUTHOR]

Facial expressions are an important form of non-verbal communication as they directly reflect the internal emotions of a person. The primary task of automated Facial Expression Recognition (FER) systems lies in extracting salient features related to facial expressions. In this paper, a Cross Connected Convolutional Neural Network (CC-CNN) has been proposed for extracting the facial features. The proposed CC-CNN model contains two levels of input for extracting the features related to facial expressions. Cyclopentane Feature Descriptor (CyFD), inspired by cyclopentane's structure, has been proposed to extract significant features. The feature response map generated by the CyFD method has been given as input to the first level, and in the second level, the features have been extracted directly from the facial image. The input images from both levels are passed through a series of convolutional layers with cross connections for extracting the fused (local and global) features related to facial expressions. Finally, towards the end, the CC-CNN method works by fusing all the features extracted from both levels. To validate the efficiency of the proposed CC-CNN method, the experiments have been performed on benchmark FER datasets such as CK+, MUG, RAF, FER2013 and FERG. The comparison results from the experimental analysis revealed that the proposed model outperformed the recent FER methods. [ABSTRACT FROM AUTHOR]

The TetraEther indeX of 86 carbon atoms (TEX 86) is widely used as a proxy to reconstruct past sea surface temperatures. Most current applications of TEX 86 are primarily based on analyzing the composition of isoprenoid glycerol dialkyl glycerol tetraethers (isoGDGTs) that comprise TEX 86 in sediments, with the assumption that the sedimentary isoGDGTs are mainly derived from the surface mixed layer. Here we report on the variations in the isoGDGT distribution, archaeal abundance and community through the water column of the Western Pacific Ocean, directly testing the export depth of isoGDGTs and constraining the temperature records of TEX 86. Our data show that maximum isoGDGT concentrations occurred in subsurface waters (150–200 m) with maximum archaeal abundances. The ratio between isoGDGTs bearing 2 vs. 3 cyclopentane moieties, i.e. [2/3] ratio, increased with depth, which is likely related to the shift of the archaeal community from Ca. Nitrosopelagicus-dominance to norank_f__Nitrosopumilaceae -dominance. Models based on the [2/3] ratios in the water column predicted an average export depth of isoGDGTs to sediments of around 150–200 m, consistent with the robust relationship between the compiled sedimentary TEX 86 and the annual mean subsurface temperature. Taken together, our findings support that TEX 86 records subsurface rather than surface temperatures in the open ocean. [ABSTRACT FROM AUTHOR]

This research can potentially impact the silver nanoparticle synthesis field significantly. The study describes the synthesis and tentative mechanism involved in silver nanoparticles with bioactives compounds 1, 2, 3, and 4 (cyclopentane derivative, polyol, Indigo, and polymer), characterized isolates from Ficus pomifera Wall, Strobilanthes flaccidifolius Nees and Crassocephalum crepidioides (Benth.) Moore. The findings of this research, particularly the characterization of silver nanoparticles formed with three compounds using energy-dispersive X-ray analysis, X-ray diffraction, transmission electron microscopy, FTIR, and UV–Vis spectroscopy, could pave the way for future advancements in the field. The average size was reported to be 50 nm, 16 nm, and 61 nm, respectively, for compounds 1, 3, and 4. Tentative mechanisms were developed for the formation of the nanoparticles by each compound 1, 3, and 4. Compound 1 reduced silver after dehydration, evident from a new ester carbonyl peak at 1743 nm from the IR spectrum. Compound 2 failed to reduce silver ions.

We report and interpret recently recorded high-resolution infrared spectra for the fundamentals of the CH2 scissors and CH stretches of gas phase cyclopentane at −26.1 and −50 °C, respectively. We extend previous theoretical studies of this molecule, which is known to undergo barrierless pseudorotation due to ring puckering, by constructing local mode Hamiltonians of the stretching and scissor vibrations for which the frequencies, couplings, and linear dipoles are calculated as functions of the pseudorotation angle using B3LYP/6-311++(d,p) and MP2/cc-pVTZ levels of theory. Symmetrization (D5h) of the vibrational basis sets leads to simple vibration/pseudorotation Hamiltonians whose solutions lead to good agreement with the experiment at medium resolution, but which miss interesting line fractionation when compared to the high-resolution spectra. In contrast to the scissor motion, pseudorotation leads to significant state mixing of the CH stretches, which themselves are Fermi coupled to the scissor overtones. [ABSTRACT FROM AUTHOR]

The synthesis of an angular triquinane, which could serve as a suitable platform for the synthesis of several natural products (panaginsene, silphinene, senoxydene) is described. The synthesis is based on two consecutive cyclopentene annulations, where alkenes were used as latent carbonyl functionalities (via Wacker reaction), and cyclopentenone annulation was effected by aldol condensation. [ABSTRACT FROM AUTHOR]

Ignition delay times are measured for binary mixtures of cyclopentane/toluene, cyclopentane/2,4,4-trimethylpent-1-ene and ternary mixtures of cyclopentane/ iso -octane/toluene, cyclopentane/ iso -octane/2,4,4-trimethylpent-1-ene. The experiments are performed using a high-pressure shock tube and a rapid compression machine for stoichiometric mixtures in 'air', in the temperature range of 650 – 1450 K and at pressures of 25 and 40 bar. A detailed chemical kinetic model is used to simulate the experimental ignition delay times. It has been formulated using NUIGMech1.2 as the base chemistry to which has been added cyclopentane, iso -octane, 2,4,4-trimethylpent-1-ene and toluene sub-mechanisms from the literature. This work provides valuable insights into the reactivity of the blending behaviour of toluene, iso -octane and 2,4,4-trimethylpent-1-ene with cyclopentane. The model is used to understand the chemical influence of these fuels on the reactivity of cyclopentane. Reaction path and sensitivity analyses of each of the cyclopentane blends using the combined mechanism are performed and these are discussed. Our analysis furthers the understanding of binary (naphthene/aromatic, naphthene/olefin) and ternary (naphthene/ iso -alkane/olefin and naphthene/ iso -alkane/aromatic) mixtures and helps improve the development of predictive models for multi-component gasoline surrogate mixture blends. [ABSTRACT FROM AUTHOR]

Although fuel spray parameters, such as spray cone angle and penetration length, are crucial for developing high-efficiency and high-performance combustion engines, general models for predicting transient characteristics of these parameters have not been suggested. In this study, the spray characteristics of cyclopentane at sub- and transcritical conditions relevant for IC engine and rocket injections were experimentally evaluated. A single simplified model for predicting the spray cone angles and spray penetration lengths over time was developed by adopting artificial neural networks (ANN). Spray measurements were conducted by shadowgraphy and Mie scattering techniques to recognize the phase change behavior of the spray, changing the injection and chamber conditions. The ANN model was developed using a multi-layer network with six normalized inputs and four outputs. It was trained with five transient spray datasets at two subcritical and three transcritical injection conditions. It was validated with one transcritical spray dataset. The ANN prediction was assessed, and the proposed approach represents the spray characteristics of cyclopentane at sub- and transcritical conditions. According to the model results, the predicted spray parameters are in good agreement with the experimental results over a useful pressure and temperature range of 40–55 bar and 465–564 K, mean absolute percentage errors of 2.25% (shadowgraphy) and 4.92% (Mie) for the spray angles, and 1.11% (shadowgraphy) and 3.44% (Mie) for the spray penetration lengths. Moreover, the developed ANN model can predict the penetration ratio, providing information on phase changes in sprays. The developed ANN model in this study is expected to become a universal model for transient spray characteristics near the critical point. By adding the database with various fuel types and spray conditions, the universal model can be used to develop high-efficiency and high-performance combustion engines or other combustors. [ABSTRACT FROM AUTHOR]

In this research, a metal-free diastereoselective formal 1,3-dipolar cycloaddition of N-2,2,2-trifluoroethylisatin ketimines and cyclopentene-1,3-diones which can efficiently lead to the desymmetrization of cyclopentene-1,3-diones is developed. With the developed protocol, a series of tetracyclic spirooxindoles containing pyrrolidine and cyclopentane subunits can be smoothly obtained with good results (up to 99% yield and 91:9 dr). Furthermore, the methodology can be extended to trifluoromethyl-substituted iminomalonate, and the corresponding formal [3+2] cycloaddition reaction affords bicyclic heterocycles containing fused pyrrolidine and cyclopentane moieties in moderate yields with >20:1 dr. The synthetic potential of the methodology is demonstrated by the scale-up experiment and by versatile transformations of the products. [ABSTRACT FROM AUTHOR]

The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes due to the fact that components in the mixture will undergo gas–liquid phase transition at the same time. We proposed a method for separating azeotropes using hydrate formation as a solid–liquid phase transition. The feasibility of hydrate-based separation is determined by analyzing the crystal structure and chemical bonds of hydrate. Taking the azeotrope cyclopentane and neohexane in petroleum as an example, cyclopentane (95%) was purified to 98.56% yield using the proposed hydrate-based cyclopentane purification technology. However, this is difficult to achieve using conventional distillation methods. The proposed method is simple in operation and yields a good separation effect. This study provides a new method for separating cyclopentane and neohexane. [ABSTRACT FROM AUTHOR]

A dedicated heat exchanger model is introduced for the optimization of heavy-duty diesel engines. The model is a prerequisite for the execution of CFD simulations, which are used to improve waste heat recovery in these systems. Several optimization methods coupled with different types of working fluids are compared in terms of exergy efficiency and heat exchanger complicity. The three considered optimization methods all lead to significant improvements in the R245fa and R1233zd systems with a comparatively low evaporation temperature. The optimal R245fa system has the highest efficiency increase (77.49%). The cyclopentane system displays the highest efficiency among the optimized ORC (Organic Rankine Cycle) systems, yet achieved by using a much heavier evaporator HEC (Heat Exchanging Core). In contrast, the 96.84% efficiency increase for the optimized R1233zd is achieved with only 68.96% evaporator weight. [ABSTRACT FROM AUTHOR]

2,2-Disubstituted 1,3-cyclopentanediones are versatile building blocks for synthesizing complex natural products with bicyclic structures including cyclopentane rings. The reported method for the synthesis of these compounds involves the semi-pinacol rearrangement of a Mukaiyama aldol adduct prepared from a ketone/ketal and 1,2-bis(trimethylsilyloxy)cyclobutene. However, the adoption of α-oxy-functionalized ketones/ketals is quite difficult, as demonstrated by our experiments. To overcome this limitation of the method, 2-acylfuran derivatives were used as the reactants to synthesize 2,2-disubstituted 1,3-cyclopentanediones. Furthermore, two reaction conditions, that is, the use of 1.4 equivalents of a boron trifluoride-diethyl ether complex or 0.4 and 0.2 equivalent of trimethylsilyl triflate and methoxytrimethylsilane, respectively, were established for the conversion of 2-acylfurans into the corresponding 1,3-cyclopentanediones in acceptable yields. The transformations of the furan rings in the obtained products were also investigated. [ABSTRACT FROM AUTHOR]

A short synthetic sequence to a linear triquinane is reported involving [3+2] cycloaddition, oxidative cleavage of double bond using ruthenium catalyst followed by decarboxylation. By this methodology, norbornene double bond can be easily cleaved to obtain the linear triquinane unit. This methodology is useful for the synthesis of natural and non-natural products having fused cyclopentane ring systems. [ABSTRACT FROM AUTHOR]

A new class of indolotacrine hybrids including cyclopenta- and cyclohexa-indolotacrine derivatives was designed, synthesized, and assessed as acetylcholinesterase inhibitors (AChEIs). Some of the designed derivatives indicated a good inhibitory effect against acetylcholinesterase (AChE). Among them, cyclopenta-indolotacrine hybrids showed a slightly better anti-AChE activity than cyclohexa-indolotacrine hybrids. Compound 5-amino-4-(4-chlorophenyl)-2-(1H-indol-3-yl)-4,6,7,8-tetrahydrocyclopenta[b]pyrano[3,2-e]pyridine-3-carbonitrile (8g) including 4-chlorophenyl and cyclopentane ring showed the best AChE inhibitory activity with IC50 value of 0.4 µM. The kinetic study indicated that compound 8g acted as a competitive inhibitor. Based on molecular docking results, it occupied both the catalytic anionic site (CAS) and peripheral anionic site (PAS) of AChE. Using a neuroprotective assay against H2O2-induced cell death in PC12 neurons, only compound 8b with 4-methoxyphenyl moiety and cyclopentane ring illustrated significant protection (P < 0.0001) at a concentration of 100 μM compared to quercetin at a concentration of 10 μM (P < 0.0001). In silico ADME studies estimated good drug-likeness for the designed compounds. As a result, these indolotacrine hybrids can be a very encouraging AChE inhibitor to treat Alzheimer's disease. [ABSTRACT FROM AUTHOR]

The isochoric heat conductivity in plastic phases I and II solid cyclopentane(C5H10) is investigated. Various temperature dependents of heat conductivity indicate various characteristics of a rotary motion of molecules in these phases. In phase II, the motion of the molecules has mainly character of libration, and in phase I, is close to the hindered rotation. In a phase I of cyclopentane an increase in the slope of isochoric heat conductivity with the growth of the density of samples is revealed. Such behavior of heat conductivity is not characteristic of molecular crystals and can point to a contribution of "pseudorotation" to heat transfer. In phase II, cyclopentane the behavior of heat conductivity is close to a case of strong scattering of phonons. [ABSTRACT FROM AUTHOR]

In this study, the dynamic viscosity of hydrocarbons was studied. This study was carried out with phenomenological aspects. The objects that were selected for this study are as follows: Cyclopentane, methylcyclopentane, ethylcyclopentane, propylcyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane. The studies were carried out in the temperature range T = 2 5 3 –373 K. It has been established that with the increasing temperature, the value of the dynamic viscosity of hydrocarbons decreases. In these materials, the mechanism of change in dynamic viscosity at high temperatures has been studied. [ABSTRACT FROM AUTHOR]

Alkane mixtures are important chemicals used in different fields. The pρTx data of the mixtures are essential for the establishment of the equation of state. In this work, the liquid densities of cyclopentane/n-octane mixtures at temperatures from 293.15 K to 363.15 K and at pressures up to 70 MPa were reported for the first time. The measurements were carried out using the experimental system based on the vibrating tube method. The combined expanded uncertainty for the present density measurement was evaluated to be less than 0.8 kg·m−3. Experimental density data of the cyclopentane/n-octane mixtures were fitted as the modified Tammann–Tait equation. The derived thermodynamic properties including isothermal compressibility (kT) and thermal expansivity (αp) were determined from the modified Tammann–Tait equation, and the results were analyzed. In addition, the PC-SAFT equation combined with Berthelot–Lorentz mixing rule was used to predict the densities of the mixtures, and the results show that the PC-SAFT equation can give good results for cyclopentane/n-octane mixtures when the binary interaction coefficient set to zero. [ABSTRACT FROM AUTHOR]

An enantioselective aza-Piancatelli rearrangement has been developed using a chiral Brønsted acid based on pentacarboxycyclopentadiene (PCCP). This reaction provides rapid access to valuable chiral 4-amino-2-cyclopentenone building blocks from readily available starting material and is operationally simple.

An efficient TsOH-catalyzed consecutive biscyclization cascade reaction of dithioallylic alcohols with 1-styrylnaphthols is demonstrated for the concise construction of pharmaceutically important cyclopenta[b]dihydrobenzofuran scaffolds. This process involved an acid-catalyzed (3+2) cycloaddition followed by an intramolecular nucleophilic addition, providing cyclopenta[b]dihydronaphthofurans bearing a tetra- or fully substituted cyclopentane core in good yields with exclusive diastereoselectivities (>20 : 1 d.r.). [ABSTRACT FROM AUTHOR]

Stimulated by a suggestion of the late Professor Jack D. Dunitz, that perdeuterated Janus face cycloalkanes may be more polar than their unlabelled forms, the deuterated isotopologue of all cis‐1,2,3,4,5,6‐hexafluorocyclohexane ([2H6]‐1a) and all cis‐1,2,3,4‐tetrafluorocyclopentane ([2H6]‐3a) were prepared. Computation at the B3LYP−D3 level indicated that [2H6]‐1a is not more polar than its protio form 1, however perdeuterated cyclopentane [2H6]‐3a may indeed be more polar than 3, although the magnitude is predicted to be small. None‐the‐less retention time analysis on a reverse phase GC/MS column of an add‐mix of 3 and [2H6]‐3a gave some indication that the per‐deuterated isotopologue 3a was detected marginally before the unlabelled compound consistent with increased polarity associated with perdeuteration. [ABSTRACT FROM AUTHOR]

There are several flow assurance problems for the energy development in deep-water, the coexistence of wax and hydrate resulting to multi-solid phase deposition is among the most difficult to overcome. The results of an experimental study on the effect of wax content, water cut, subcooling and static time on the CP hydrate-forming mixtures are reported. The droplet distribution at different wax contents is determined by using microscopic observation method. Using dynamic stress measurements method, a correlation between rheological properties and water cut is obtained. Hydrate nucleation, growth, dissociation, and slurry rheological properties, including critical time, growth time, final viscosity, and yield properties are determined. Results indicated that wax inhibit hydrate nucleation and growth, but the viscosity of hydrate slurry in waxy system is still higher than wax-free system due to the wax-hydrate aggregates contribute more to the viscosity of the system. The structure of hydrate slurry containing wax system is more stable and more difficult to be damaged by shear. Wax increases the hydrate slurry yield stress, and this effect is more significant at higher water cut and longer static times. The yield stress of the hydrate slurry was linearly related to the water cut. 35% was the critical water cut. Below the critical water cut, the slurry had better flow ability and less yield stress. Above the critical water cut, the yield stress increased significantly with water cut. The yield stress increased with increasing static time and decreases with increasing temperature. Nevertheless, the coupling effect of temperature with water cut and wax content was complex. Below 3 wt% wax content, temperature only has a significant effect on the yield stress of slurries with 40% and 50% water cut. Above 3 wt% wax content, temperature has a significant effect on the yield stress of all slurries with a 20–50% water cut. No ice formation in the CP hydrate-forming mixtures at −4°C, and the dissociation temperature of the hydrate decreases as the concentration of CP in the oil phase decreases. [ABSTRACT FROM AUTHOR]

R. Stephen Berry (1931–2020) was a Harvard-educated American pioneer of molecular structure studies. He is most famous for the phenomenon of Berry pseudorotation and his studies of intramolecular motion and molecular fluxionality. This remembrance focuses on this discovery. He had broad interests in many other aspects of structural chemistry and physical chemistry and also in the economics of energy. [ABSTRACT FROM AUTHOR]

Hydrate‐based desalination could be a promising technique for producing fresh water from saline water, as it is an eco‐friendly process and suitable for large‐scale implementation. To make the hydrate‐based desalination technology easily scalable, we looked at using air (or N2) or CO2 as a hydrate former, along with cyclopentane (CP). Hydrate former CP helps to reduce the operating conditions, as CP forms hydrate at ambient pressure. However, hydrate formation kinetics due to water‐insoluble CP is slow. In this work, the kinetics of hydrate formation in saline water were investigated and compared to identify the utility of CO2 and N2 as hydrate formers for desalination work. The addition of CP as a hydrate former should transform the structure of CO2 hydrate from structure I (sI) to structure II (sII), as CP occupies the large cages (51264) in the gas hydrate. A set of three similar reactors were used for this study to collect data quickly. Furthermore, the triple reactor setup is a unique reactor design mounted on a shaker, and a set of SS‐316 balls present inside the horizontal reactor imparts the mixing. Experiments with the CO2‐CP mixture and N2‐CP mixture have been studied in the presence or absence of 3 wt.% NaCl at 274 K and 3 MPa pressure. The gas uptake kinetics, water recovery, and separation efficiency have been investigated. [ABSTRACT FROM AUTHOR]

This study reports thermodynamic properties and crystal growth observations of D2O + cyclopentane hydrate toward the development of a hydrate‐based tritium separation process. We employed D2O as a host of hydrate with respect to the investigation into the formation of D2O hydrate substrate, which is a core component of the tritium separation process. The hydrate phase equilibrium temperature in the liquid D2O + liquid cyclopentane system was 3.2°C higher than the corresponding H2O hydrate. Experiments on crystal growth were conducted at temperatures ranging from 5.1 to 8.5°C under atmospheric pressure. Under each thermodynamic condition, polygonal hydrate crystals appeared, growing along the D2O/cyclopentane interface. The geometric shape and size of the crystals varied depending on the temperature. The variation in crystal morphology was comparable to that of the H2O + cyclopentane hydrate. Implications based on the obtained results for the hydrate‐based isotopic water separation process design are discussed. [ABSTRACT FROM AUTHOR]

The success of geological storage of carbon dioxide (CO2) in depleted oil and gas reservoirs relies among other aspects on the efficiency of CO2 injection, especially in the near-wellbore area where flow rates are high. CO2 hydrates pressure/temperature equilibrium conditions may be reached in this zone due to cooling associated with the Joule–Thomson effect; such CO2 hydrate formation may lead to strong injectivity loss and impair drastically the onsite well operations. In this study, cyclopentane hydrates (CPH) were employed as CO2 hydrate proxy (i.e. formation at atmospheric pressure) to mimic CO2 hydrate formation at higher pressure. In this study, the nucleation and growth processes were determined using a droplet-based in-house-microfluidic device. The generation of water droplets in cyclopentane liquid using the co-flow method was achieved. Trains of identical water droplets were stored in a serpentine channel. Each isolated droplet in this channel serves as a separate reactor. The temperature was controlled using a Peltier module to initiate hydrate nucleation at low temperatures. The isolated droplets provided the opportunity to statistically analyze the kinetic behaviors by varying key parameters, such as thermal history and water salinity. Detection of the onset of crystallization in water droplets over time and temperature allowed us to plot conversion curves based on imposed parameters. The effect of thermal history and dissociation temperature was first compared using pure water. This study marks the initial investigation into how NaCl influences CPH formation in microfluidic devices, focusing on isolated water droplets within serpentine tubes. The progression of ice nucleation, ice melting, the onset of CPH crystallization, CPH growth, and CPH dissociation are illustrated in water droplets exposed to changing temperatures. The addition of NaCl in the water during the procedure exhibited a noteworthy impact on CPH formations. With the same temperature profile, salt concentration delays nucleation (thermodynamic effect) and slows down growth. Our findings suggest that higher subcooling accelerates nucleation and growth rates. Initial lateral growth rates ranged from 4.22 μm/s to 2.14 μm/s, with a subcooling of 4.2 °C observed between 2 and 7 min for a pure water droplet. [ABSTRACT FROM AUTHOR]

Ring structures such as pyridine, cyclopentane or their combinations are important motifs in bioactive molecules. In contrast to previous cycloaddition reactions that necessitated a directly bonded initiating functional group, this work demonstrated a novel through‐(hetero)arene radical transmission concept for selective activation of a remote bond. An efficient, metal‐free and atom‐economical [3+2] cycloaddition between 4‐pyridinyl cyclopropanes and alkenes or alkynes has been developed for modular synthesis of pyridine‐substituted cyclopentanes, cyclopentenes and bicyclo[2.1.1]hexanes that are difficult to access using known methods. This complexity‐building reaction was catalyzed by a very simple and inexpensive diboron(4) compound and took place via dearomative/rearomative processes. The substrate scope was broad and more than 100 new compounds were prepared in generally high yields. Mechanistic experiments and density function theory (DFT) investigation supported a radical relay catalytic cycle involving alkylidene dihydropyridine radical intermediates and boronyl radical transfer. [ABSTRACT FROM AUTHOR]

Clouding behavior and thermodynamic properties for the TX 100 + BSA mixture were investigated in aqueous and aq. alcoholic media. In an aqueous environment, the values of cloud point (CP), at which a clear solution becomes cloudy, for TX 100 decreases with augmentation of the concentration of BSA. The reverse result was obtained in the aq. alcoholic media. In this study, we have used ethanol (EtOH), 1-propanol (1-PrOH), and 2-butanol (2-BuOH) as alcohols. The changes of CP values in alcoholic media have been obtained in the following order: CP H 2 O+EtOH > CP H 2 O+2−BuOH > CP H 2 O+1−PrOH. The standard free energy (∆ G c o ), standard enthalpy (∆ H c o ), and standard entropy (∆ S c o ) changes of clouding were derived at CP. The Δ G c 0 values of TX 100 + BSA decreases in the aqueous and alcoholic media with increasing the concentration of BSA and alcohol. This process becomes endothermic in the aq. alcoholic media. Different thermodynamic properties of transfer and entropy-enthalpy compensation parameters for the phase partitioning of the TX 100 + BSA mixture have been calculated and assessed properly. [ABSTRACT FROM AUTHOR]

Herein, we have synthesized a variety of cycloalkane‐fused arsoles. Cyclopentane and cyclohexane were incorporated into the cycloalkane‐fused arsoles. Surprisingly, cyclohexane‐fused arsole 2 a gradually decomposed via oxidative ring‐opening under ambient conditions, while cyclopentane‐fused 1 a was stable. In addition, the Stokes shift of 2 a (7766 cm−1) is larger than that of 1 a (5120 cm−1). The effects of the fused cycloalkane on the stability and photophysical properties were attributed to the distortion of the cycloalkane. Computational calculations demonstrated that the cyclohexane moiety in 2 a was frustrated upon being incorporated into the rigid arsole ring, while the cyclopentane moiety in 1 a was much less distorted. [ABSTRACT FROM AUTHOR]

The vapor–liquid phase equilibrium (VLE) data for binary systems of neohexane + cyclopentane, neohexane + N,N-dimethylformamide (DMF), cyclopentane + DMF and ternary system of neohexane + cyclopentane + DMF were determined with a modified Rose still at 101.3 kPa, and all the binary data passed the Wisniak's test (D < 5), which accorded with the thermodynamic consistency. Three activity coefficient models namely, Wilson, NRTL and UNIQUAC were used to correlate VLE data and get binary interaction parameters, then the ternary VLE data of neohexane + cyclopentane + DMF were estimated based on these model parameters using Aspen Plus software. The estimation values of the three models agree well with the experimental data (σ(T) < 0.5 K). Moreover, the analysis of the effect of DMF on the vapor–liquid phase equilibrium shows that DMF can act as an effective extractant for the system studied. [ABSTRACT FROM AUTHOR]

Carbocycles are a key and widely present structural motif in organic compounds. The construction of structurally intriguing carbocycles, such as highly-strained fused rings, spirocycles or highly-functionalized carbocycles with congested stereocenters, remains challenging in organic chemistry. Cyclopropanes, cyclobutanes and cyclopentanes within such carbocycles can be synthesized through ring contraction. These ring contractions involve re-arrangement of and/or small molecule extrusion from a parental ring, which is either a carbocycle or a heterocycle of larger size. This review provides an overview of synthetic methods for ring contractions to form cyclopropanes, cyclobutanes and cyclopentanes en route to structurally intriguing carbocycles. [ABSTRACT FROM AUTHOR]

[Display omitted] The effects of hydrate inhibitors on the adhesion of sintered hydrate deposits on pipe walls are still unexplored. Herein, a custom-built adhesion strength measurement apparatus was utilized to quantify the adhesion strengths of sintered cyclopentane (CyC5) hydrate deposits with thermodynamic inhibitors (ethylene glycol, glycerol) and low-dosage inhibitors (dodecylbenzene sulfonic acid (DBSA), sorbitan oleate (Span 80)). It was found that the hydrate adhesion strengths decreased by 69.82%-97.06% and 40.24%-94.36% with the concentration of ethylene glycol and glycerol increased from 2 wt% to 6 wt%, respectively. For DBSA and Span 80, the hydrate adhesion strength increased with concentration less than 0.01 wt% due to the acceleration on hydrate growth. The further increment of concentration leads to a dramatic reduction in adhesion strengths. Furthermore, the relatively large deviations with the predicted strengths led to the discussions of the effects of change in hydrate formation rate, crystal morphology, and also the adaption of the fitting model. Two modified models were proposed to give a better prediction/explanation of the hydrate adhesion with thermodynamic inhibitors and low-dosage inhibitors, respectively. This work provides a fundamental understanding of the adhesion mechanism of hydrate deposits with hydrate inhibitors, which is important in advancing the management of hydrate formation for preventing plugging in pipelines. [ABSTRACT FROM AUTHOR]

Molecular salts formation is a simple and widely used approach to alter the physicochemical properties of active pharmaceutical ingredients, such as ciprofloxacin (CP), without modifying their chemical structures. In the current work, two co-crystals of p-coumaric acid (PCMA) and organic salts of CP cation (CPH) were prepared and characterized in solid state by X-ray diffraction and by NMR spectroscopy in solution. The two organic salts are CPH:benzoate anion (CPH:BA) and CPH:salicylate anion (CPH:SA). To our knowledge, these are the first two examples of co-crystals of CPH organic salt and a different organic acid. In the two co-crystals (CPH:BA:PCMA and CPH:SA:PCMA), the anion (BA or SA) connects the PCMA molecules and the CPH via O–H∙∙∙O and N–H∙∙∙O hydrogen bonding interactions. The ratio between the three crystalline species in the two co-crystals (CPH:BA:PCMA and CPH:SA:PCMA) is (1:1:1), the ratio was confirmed in solution by NMR spectroscopy. Co-Crystals of ciprofloxacinuim cation salts of salicylate or benzoate anions and p-coumaric acid have been studied in solution using NMR spectroscopy and in solid state using X-ray crystallography [ABSTRACT FROM AUTHOR]

Freshwater scarcity is a critical issue in Vietnam, particularly in the Mekong Delta, a densely populated region with an agriculture-based economy. This scarcity is largely driven by saltwater intrusion during the dry season, severely affecting both agriculture and the local economy. In response, advanced desalination technologies have been proposed. In this study, we investigated the use of cyclopentane (CP), a liquid guest molecule, and 1,1,1,2-tetrafluoroethane (R134a), a gaseous guest molecule, as hydrate formers to desalinate saline water from the Mekong Delta. This study aimed to evaluate and compare the freshwater recovery efficiencies of these hydrate formers and assess the potential of hydrate technology for practical application in the region. We performed thermodynamic and kinetic investigations on sodium chloride solutions (1.0-3.5 wt%), representing the salinity levels of seawater in the Mekong Delta, to establish a laboratory-scale desalination system. The results showed a consistent thermodynamic trend: the higher concentration of samples leads to the longer time of hydrate formation to achieve the conversion of water into hydrates exceeding 60 %. Additionally, the CP and R134a hydrate structures were characterized using Raman spectroscopy, which revealed significant changes in the water peak and C-H band signal during the hydrate formation process. After a single-stage hydrate treatment using CP and R134a, the removal efficiencies for ions and total dissolved solids in saline water samples from the Mekong Delta exceeded 75 % and 70 %, respectively. These findings serve as a reference for developing a larger-scale hydrate-based desalination technology to address the challenges of saltwater intrusion in the Mekong Delta region., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors. Published by Elsevier Ltd.)

The separation of azeotropic mixtures has conventionally been one of the most challenging tasks in industrial processes due to the fact that components in the mixture will undergo gas–liquid phase transition at the same time. We proposed a method for separating azeotropes using hydrate formation as a solid–liquid phase transition. The feasibility of hydrate-based separation is determined by analyzing the crystal structure and chemical bonds of hydrate. Taking the azeotrope cyclopentane and neohexane in petroleum as an example, cyclopentane (95%) was purified to 98.56% yield using the proposed hydrate-based cyclopentane purification technology. However, this is difficult to achieve using conventional distillation methods. The proposed method is simple in operation and yields a good separation effect. This study provides a new method for separating cyclopentane and neohexane.

Cyclopentenes are common cores in many natural products, and in bioactive and functional molecules. However, their synthesis remains challenging in terms of harsh conditions, poor selectivity, prefunctionalization of the substrates, over‐reliance on volatile activating reagents and the use of noble metals. Herein, we develop an electrochemical mediator‐induced intermolecular selective (3+2) annulation of readily available alkenes and alkynes/alkenes, which provides a simple and efficient method for the synthesis of a library of decorated cyclopentenes and cyclopentanes. This protocol features high efficiency, mild reaction conditions, broad substrate scope, good functional group tolerance, and high regioselectivity. Potential applications are demonstrated by gram‐scale synthesis as well as the construction of structural diversity and complexity. A preliminary mechanistic investigation was performed, which indicated that an iodine radical and carbon radicals are involved in this transformation. [ABSTRACT FROM AUTHOR]

A red-light-mediated [3+2] annulation of cyclopropylamines with akenes or alkynes in the presence of N , N ′-dipropyl-1,13-dimethoxyquinacridinium is reported. An array of cyclopentane or cyclopentene derivatives with diverse functional groups have been obtained in moderate to excellent yields under mild conditions. [ABSTRACT FROM AUTHOR]

Heat generation during gas hydrate formation is an important problem because it reduces the amount of water and gas that become gas hydrates. In this research work, we present a new design of an impeller to be used for hydrate formation and to overcome this concern by following the hydrodynamic literature. CH4 hydrate formation experiments were performed in a 5.7 L continuously stirred tank reactor using a butterfly turbine (BT) impeller with no baffle (NB), full baffle (FB), half baffle (HB), and surface baffle (SB) under mixed flow conditions. Four experiments were conducted separately using single and dual impellers. In addition to the estimated induction time, the rate of hydrate formation, hydrate productivity and hydrate formation rate, constant for a maximum of 3 h, were calculated. The induction time was less for both single and dual-impeller experiments that used full baffle for less than 3 min and more than 1 h for all other experiments. In an experiment with a single impeller, a surface baffle yielded higher hydrate growth with a value of 42 × 10−8 mol/s, while in an experiment with dual impellers, a half baffle generated higher hydrate growth with a value of 28.8 × 10−8 mol/s. Both single and dual impellers achieved the highest values for the hydrate formation rates that were constant in the full-baffle experiments. [ABSTRACT FROM AUTHOR]

A protocol for the enantioselective synthesis of substituted vinylcyclopentanes has been realised using cooperative palladium and isothiourea catalysis. Treatment of vinylcyclopropanes with Pd(PPh3)4 generates a zwitterionic π‐allyl palladium intermediate that intercepts a catalytically generated α,β‐unsaturated acyl ammonium species prepared from the corresponding α,β‐unsaturated para‐nitrophenyl ester and the isothiourea (R)‐BTM. Intermolecular formal (3+2) cycloaddition between these reactive intermediates generates functionalised cyclopentanes in generally good yields and excellent diastereo‐ and enantiocontrol (up to >95 : 5 dr, 97 : 3 er), with the use of LiCl as an additive proving essential for optimal stereocontrol. To the best of our knowledge a dual transition metal/organocatalytic process involving α,β‐unsaturated acyl ammonium intermediates has not been demonstrated previously. [ABSTRACT FROM AUTHOR]