Organic Solvent Molecules Research Articles

Experimental and Predicted Crystal Energy Landscapes of Chlorothiazide

An experimental search for physical forms of the thiazide diuretic compound chlorothiazide comprising 402 different crystallizations identified one nonsolvated form and ten crystalline solvates. There are five distinct conformations in the experimental crystal structures which are in good agreement with the conformational minima found by ab initio optimization of the isolated molecule structure. An approximate rigid-body crystal energy landscape using these five conformations produced a diverse range of low energy crystal structures, with the anhydrous structure among the most stable. Inspection of the molecular packing adopted in both the experimental and predicted structures highlighted a number of chlorothiazide···chlorothiazide motifs that result from packing the different conformers. Specifically, four bimolecular face-to-face motifs were observed in most of the predicted structures and all of the experimental structures. The role of these robust intermolecular packing motifs and of the organic solvent molecules in stabilizing the experimental solvate structures of chlorothiazide is discussed. The results highlight the value of the approximate crystal energy landscape for flexible organic molecules in assisting with the interpretation of solid-state diversity in chlorothiazide crystal structures and identifying key stabilizing packing features.

Kinetics of 1H→ 13C NMR cross-polarization in polymorphs and solvates of the antipsychotic drug olanzapine

The 1H→ 13C NMR cross-polarization (CP) was studied under magic-angle spinning at 7.5 kHz in various crystal forms of the antipsychotic drug olanzapine: two polymorphs (metastable I and stable II) and eight solvates containing organic solvent and water molecules. The CP kinetics followed the non-classical I–I ⁎-S model, in which CP begins in a spin cluster of proximate abundant spins I * and rare spins S, then is controlled by spin diffusion of the abundant spins I from bulk to the I * spins of the spin cluster and finally is governed by spin-lattice relaxation of the abundant spins in the rotating frame. The corresponding CP kinetics parameters were determined and analyzed. It was demonstrated that the, λ and T df values (the CP time constant, the cluster composition parameter and the 1H spin-diffusion constant, respectively) were very useful to discriminate the functional groups, especially in the 3D parameter space. In order to conveniently analyze the large amount (175) of the collected CP parameters, the number of the observed variables was reduced using the principal component (PC) analysis. The 2D plot of PC2 vs. PC1 showed adequate separation of the CH 3, CH 2, CH and C cases (C stands for carbons without adjacent hydrogens). It was demonstrated that those cases were located along the PC1 axis in the order of increasing 1H– 13C dipolar couplings: C<CH 3<CH<CH 2. Our study showed the I–I *-S model at work and established ranges of its parameters for various functional groups.

Performance of short-chain alcohols versus acetonitrile in the surfactant-mediated reversed-phase liquid chromatographic separation of β-blockers

Organic solvents are traditionally added to micellar mobile phases to achieve adequate retention times and peak profiles, in a chromatographic mode which has been called micellar liquid chromatography (MLC). The organic solvent content is limited to preserve the formation of micelles. However, at increasing organic solvent contents, the transition to a situation where micelles do not exist is gradual. Also, there is no reason to neglect the potentiality of mobile phases containing only surfactant monomers instead of micelles (high submicellar chromatography, HSC). This is demonstrated here for the analysis of β-blockers. The performance of four organic solvents (methanol, ethanol, 1-propanol, and acetonitrile) was compared in mobile phases containing the anionic surfactant sodium dodecyl sulphate in the MLC and HSC modes. The association of the organic solvent molecules with micelles gives rise to a significant loss in the elution strength of the organic solvent; whereas upon disruption of micelles, it tends to that observed in the hydro-organic mode. The elution behaviour of the β-blockers was modelled to predict the retention times. This allowed the detailed exploration of the selectivity and resolution of the chromatographic systems in relatively wide ranges of concentration of surfactant and organic solvent. The best performance in terms of resolution and analysis time was achieved using HSC with acetonitrile, being able to base-line resolve a mixture of eight β-blockers. Ethanol also provided a good separation performance, significantly improved with respect to methanol and 1-propanol. In contrast, the hydro-organic mode using acetonitrile or any of the short-chain alcohols could not succeed with the separation of the β-blockers, owing to the poorer selectivity and wider peaks.

Effects of organic solvents on the activity of free and immobilised laccase from Rhus vernicifera

Rhus laccase (RL) was covalently immobilised onto chitosan, and the effects of immobilisation on pH optimum, enzyme activity, thermostability, and re-use evaluated, using either N, N-dimethyl- p-phenylenediamine or 2,6-dimethoxyphenol as substrate. Immobilisation greatly enhanced enzyme thermostability, resulted in negligible loss of activity, and showed excellent re-use potential, with >80% relative activity retained after 15 cycles in aqueous solvent. Immobilised Rhus laccase (I-RL) was more catalytically active in both hydrophobic and hydrophilic organic solvents than free RL. With water-immiscible organic solvents, both free RL and I-RL required a minimum water content to achieve activity. With water-miscible organic solvents, in general a water content of ∼20–50% (v/v) was required to achieve activity using free RL, whereas with I-RL less water was generally required to achieve enzyme activity, and therefore considerably higher relative activity was exhibited at lower water contents. Kinetic investigations showed that the rate of substrate disappearance generally followed a pseudo-first-order law, and for evaluated water-immiscible organic solvents rate constants generally increased with decrease of hydrophobicity, however, in water-miscible organic solvents no such relationship was observed. Some discussion of the potential interactions between organic solvent molecules and enzyme active centres was provided to explain obtained results.

ChemInform Abstract: A Quantitative Discrimination Between Reversible Li+-Insertion and Irreversible Solvent Oxidation at a Lithium/Manganese-Spinel Electrode.

Abstract Oxidic Li + -insertion compounds of the donor type in aprotic Li + -electrolytes are of high practical importance as positives in rechargeable Li + -ion batteries. The manganese oxides MnO x are of special interest as host lattices due to their high reversibility and to the relatively positive potentials. However, these materials may induce irreversible anodic decomposition of the organic solvent molecules, especially towards the end of the charging process. Protons are injected into the electrolyte in this case. It is possible to evaluate these side reactions quantitatively through a measurement at the rotating ring/disk-electrode (RRDE). The disk was made of a 1 μm thick layer of MnO 2 (anodic deposit) on Pt (I) or a ceramic layer of the spinel LiMn 2 O 4 on Ti, which was fabricated after Beers’s method at a firing temperature of 400 (II) and 600°C (III). The ring was made of Pt. At the ring, protons were reduced to H 2 at a half wave potential of −0.25 V versus saturated sodium chloride electrode (SSCE). The electrolytes were 0.1 M LiClO 4 in propylenecarbonate (PC) and acetonitrile (MeCN). These measurements showed that the novel MnO x -layers behave similar to the conventional porous battery electrodes which are much thicker and are made of powdery materials. Charge stoichiometry y in Li y Mn 2 O 4 is found to increase from I to III from 0.2 to 2.0. No solvent oxidation could be detected at the potentials of the reversible Li + -intercalation peaks in cyclic voltammogram. The irreversible side reaction can be excluded therefore with a margin of error of 1–2%. This is in contrast to the former results obtained from the graphite intercalation compounds of the acceptor type (A-GIC), albeit at potentials more positive by 1 V. However, just behind the reversible Li + -deintercalation peak, i.e. charge direction, the positive end of the electrochemical window is attained. The current rises steeply. Abundant protons are injected into the electrolyte. The potentials are by 0.5–1 V more negative than at Pt due to the electrocatalytic activity of MnO x with respect to the irreversible anodic oxidation of the solvent molecules PC and MeCN.

On the Effect of Temperature on Aqueous Solubility of Organic Solids

The variation of solubility with temperature in water is an important consideration in the design of crystallizations and other processes. Solubility was found to vary exponentially with temperature (in °C) for a literature data set of 50 organic molecules in water. This complements a similar recent finding for the solubility of organic molecules in organic solvents. The ‘solubility doubling temperature’ is a convenient way to express this variation and provides a numerical link between enthalpy of dissolution and yield. The ‘solubility doubling temperature’ in water varies with solute, and the median value from this data set is 21.4 °C, consistent with ‘Black’s rule’.

Enabling Solvated Single-Crystal-to-Single-Crystal Transformation that Forms a Porous Molecular Crystal by Intermolecular Multiphenyl-Embrace Interactions and Substituent Effects

Tubular complexes, [{Ru2(CO)4(P(C6H4R)3)2}(1,4-O2CC6H4CO2)]3 (R = H, 4; p-Me, 5), were found to adopt a staggered conformation in the solid state. The complexes align themselves in one-dimensional (1-D) channels occluded with organic solvent molecules. A single-crystal-to-single-crystal transformation with both incarceration and liberation at specific sites that forms a porous molecular crystal occurs for one solvated crystals of complex 4 but not for two solvated crystals of complex 5. The data suggest that in the presence of an appropriate R substituent, the intermolecular multiphenyl-embrace interactions between adjacent P(C6H4R)3 groups of different molecules along the channel direction help form close solvent pockets to trap organic solvent molecules and serve as a multiple-point glue to connect adjacent 1-D channels, which ensures lattice stabilization during the air-drying process of the crystal.

Effect of Swelling on the Superconducting Characteristics in Electron-Doped β-ZrNCl and HfNCl

Layer-structured metal nitride chlorides M NCl ( M =Zr, Hf) were electron-doped by the intercalation of alkali metals ( A =Li and Na) to form A x M NCl, and then swelled with organic solvent molecules [tetrahydrofuran (THF) and propylene carbonate (PC)]. Upon swelling, the organic molecules were cointercalated with the alkali metals, resulting in the basal spacing of A x M NCl being expanded by 5.6–18.5 Å and the superconducting transition temperatures ( T c s) increasing by ∼2 K. When the magnetization data were plotted as a function of temperature, an irreversibility temperature ( T irr ) was observed, where the zero-field-cooled (ZFC) and field-cooled (FC) magnetization superimpose. The reversible temperature range ( T c - T irr ) was markedly increased upon swelling. The slope of the plot of log H (applied magnetic field) vs log (1- T irr / T c ) was increased for the swelled system. The slope n in the power-law relationship for Na 0.28 (PC) y HfNCl and Li 0.5 (THF) y HfNCl is obtained to be n = 4.8–5.4. This finding implies a significant weakening of vortex pinning in the swelled phase. To investigate the irreversibility microscopically, nuclear magnetic resonance (NMR) measurements were carried out on Li 0.5 (THF) y HfNCl. The 1 H- and 7 Li-NMR relaxation and chemical shift suggested the relevance of vortex motions to the depinning at T irr , which is the depinning temperature between the thermally excited pancake vortex liquid state at higher temperatures and the pancake vortex glass state at lower temperatures.

A flexible supramolecular host with a crowned chair octameric water cluster and highly selective adsorption properties

A novel supramolecular host {[Fe(CN)6]·(H-bipy)3·8H2O} (1) was obtained by the reaction of K3[Fe(CN)6] and 4,4′-bipyridyl (bipy) under an acidic medium (pH ≈ 3). The supramolecular structure of 1 is made up of non-covalent forces viz. hydrogen bonding and π–π interactions. The host houses a discrete octameric water cluster with the conformation of a 1,4-substituted cyclohexane molecule where six water molecules are positioned on the vertices of the cyclohexane ring and the seventh and eighth occupy the 1,4-equatorial positions of the ring. DFT calculations suggest that this conformation is more stable (−73.08 kcal mol−1) when compared to the a,a conformation. Upon removal of the water molecules, the host network of 1 undergoes a structural transformation and the dehydrated phase exhibits a stepwise uptake of H2O vapour and completely excludes CO2 and other organic solvent molecules (CH3OH, CH3CN and EtOH).

Phase separation in the system with sodium silicate and sodium dodecyl sulfate under acidic conditions

Phase separation in an acidic aqueous solution with sodium silicate and sodium dodecyl sulfate (SDS) was investigated. The solution separated into silica-rich and SDS-rich phases during condensation of silica components. During the phase separation, the transition structure was fixed by gelation, resulting in mutually continuous morphology. The addition of a small amount of water-miscible organic solvents, such as methanol, ethanol, 1-propanol, and 1-butanol, into the reacting solution greatly decreases both viscosity and phase separation tendency of the solution. In the system with high concentration of strong acid, SDS molecules form wormlike micelles, which not only increase viscosity of the solution but also play an important role in the phase separation in the solution because the formation of wormlike micelles increases apparent molecular weight of SDS and decreases mixing entropy. The decrease in the viscosity by the addition of organic solvents suggests that wormlike micelles become small in the presence of organic solvent molecules. Consequently, the addition of appropriate amount of organic solvent is effective for controlling phase separation tendency and size of the resulted macropores in the system with SDS through the change in the structure of the micelles.

Investigation of the driving forces for retention in reversed-phase liquid chromatography: Monte Carlo simulations of solute partitioning between n-hexadecane and various aqueous–organic mixtures

With the aim of learning about the solubility characteristics of retentive and mobile phases often encountered in reversed-phase liquid chromatography (RPLC) and to examine the driving forces for retention, configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out for systems consisting of three phases: an n-hexadecane retentive phase (serving as a model of the hydrophobic RPLC stationary phase), a mobile phase with varying water–acetonitrile or water–methanol composition, and a helium vapor phase (serving as an ideal gas reference state). Gibbs free energies of transfer between each of these phases were computed for a series of small alkane and alcohol solutes and from these the methylene and hydroxyl increments were determined. The results indicate that both nonpolar and polar solutes have favorable interactions with both the mobile and stationary phase thus showing that neither the solvophobic theory nor lipophilic theory alone can explain the driving forces for retention in RPLC. In addition, an analysis of the solvation environments of methylene and hydroxyl groups in the mobile and stationary phases was carried out. The methylene group is shown to be preferentially solvated by the organic component of the aqueous–organic mixture, however, clustering of the organic solvent molecules in the absence of the solute was not observed. For the hydroxyl group, hydrogen bonding was shown to be important in both the mobile and stationary phases.

Photophysical properties of phenanthro[9,10- d]imidazole-type fluorescent hosts upon inclusion of organic solvent molecules

The crystal of phenanthro[9,10- d]imidazole-type fluorescent clathrate host ( 1) exhibits fluorescence enhancement behavior with a blue-shift of the emission maximum upon enclathration of organic solvent molecules such as 1-butanol and morpholine, whereas the crystal of 1 exhibits fluorescence enhancement behavior with a red-shift of the emission maximum upon enclathration of carboxylic acid such as acetic acid and propionic acid. The crystal structures of the guest-free and the guest-inclusion compounds of 1 have been determined by X-ray analysis. On the bases of the spectral data and the crystal structures, the effects of the enclathrated guest molecule on the solid-state photophysical properties of the guest-inclusion compounds are discussed.

Solvatochromic Fluorescence of Piperazine-Modified Bipyridazines for an Organic Solvent-Sensitive Film

Bipyridazines were modified with heterocyclic amines such as piperazine to give symmetric quadrupolar (SPBP) and asymmetric dipolar (APBP) bipyridazine. The fluorescence of SPBP and APBP was highly sensitive to solvent polarity, giving a synthetic rainbow of emission in different organic solvents. The solvent-induced changes in the Stokes shift of the bipyridazines resulted in positive solvatochromism. The symmetric bipyridazine showed higher solvatochromic sensitivity than that of the asymmetric bipyridazine and diazines. The positive solvatochromic fluorescence properties were reproduced in a binary system of toluene/dimethyl sulfoxide (DMSO) mixture, which showed a synthetic rainbow of emission by varying the DMSO content in toluene. An organic sensitive poly(methyl methacrylate) film containing SPBP exhibited a visible sensitivity for the detection of solvents by their polarity upon exposure to organic solvent molecules.

Have the primary structures of biomacromolecules been selected in a Darwinian fashion to adapt to the surrounding environments of our planet?

Have the primary structures of biomacromolecules been selected in a Darwinian fashion to adapt to the surrounding environments of our planet?

Excess Adsorption of Commonly Used Organic Solvents from Water on Nonend-Capped C18-Bonded Phases in Reversed-Phase Liquid Chromatography

The excess adsorption isotherms of methanol, 2-propanol, acetonitrile, and tetrahydrofuran from water were measured on five silica-based packing materials by the minor disturbance method. The adsorbed amount of solvents was calculated per silica gel surface and per modeled surface of bonded phase which seem to give more correct data. Columns used in this study were nonend-capped with different coverage density of bonded C18 ligands. It allows investigating the influence of the density of residual silanols on the solvent adsorption and on adsorption properties of the surface. The stationary phases were characterized by elemental analysis and low-temperature nitrogen adsorption. Geometric parameters of the stationary phases in the column were measured by inverse size exclusion chromatography. The relative adsorption of the organic solvents from water informs on the heterogeneity of the stationary phases and on the accessibility of the unreacted silanol groups to the mobile phase. The differences in the organic solvent and water molecules for interaction with organic ligand and residual silanols are used for the estimation of the surface heterogeneity.

Solvent effect on the distribution equilibrium of 8-quinolinol derivatives between supercritical carbon dioxide and water

The distribution constants ( K D,C O 2 ) of 8-quinolinol derivatives (HA) between supercritical carbon dioxide (SC-CO 2) and water were determined at 45 °C. The values of K D,C O 2 increased with an increase in the SC-CO 2 pressure, that is, the SC-CO 2 density ( ρ C O 2 ) . The values of K D,C O 2 were evaluated by a comparison of the distribution constant ( K D,org) of HA between heptane and water. Based on a linear relationship between log K D,org and log K D,C O 2 , it was suggested that the interaction of heptane molecules with HA is similar to that of CO 2 molecules. The solvent effect on the distribution behaviors of HA between SC-CO 2 and water was evaluated based on a regular solution theory. The solubility parameters of HA in the SC-CO 2–water extraction system are smaller than those in the organic solvent–water extraction system, suggesting that the interaction between HA and CO 2 molecules, such as the dispersion force, dipole–dipole and dipole-induced dipole interactions, is weaker than that between HA and the organic solvent molecules.

Hybrid Thermoreversible Gels from Covalent Polymers and Organogels

This paper reports on experiments intended for investigating the feasibility of preparing hybrid thermoreversible gels from covalent polymers and noncovalent self-assembling pi-conjugated molecules. The formation and the degree of dispersion of these hybrid gels have been studied with polystyrenes of various tacticities and oligo(p-phenylenevinylene) molecules (OPV) in different nonpolar organic solvents. Detailed investigations of the systems have been carried out by DSC, SAXS, and AFM. It is shown that no liquid-liquid phase separation is involved, indicating that the systems are highly compatible, and that the growth of one type of gel does not interfere with the other. These studies reveal that the resultant hybrid gels are composed of the intermingled fibrillar architectures of both gels.

Multiple solvent crystal structures of ribonuclease A: An assessment of the method

The multiple solvent crystal structures (MSCS) method uses organic solvents to map the surfaces of proteins. It identifies binding sites and allows for a more thorough examination of protein plasticity and hydration than could be achieved by a single structure. The crystal structures of bovine pancreatic ribonuclease A (RNAse A) soaked in the following organic solvents are presented: 50% dioxane, 50% dimethylformamide, 70% dimethylsulfoxide, 70% 1,6-hexanediol, 70% isopropanol, 50% R,S,R-bisfuran alcohol, 70% t-butanol, 50% trifluoroethanol, or 1.0M trimethylamine-N-oxide. This set of structures is compared with four sets of crystal structures of RNAse A from the protein data bank (PDB) and with the solution NMR structure to assess the validity of previously untested assumptions associated with MSCS analysis. Plasticity from MSCS is the same as from PDB structures obtained in the same crystal form and deviates only at crystal contacts when compared to structures from a diverse set of crystal environments. Furthermore, there is a good correlation between plasticity as observed by MSCS and the dynamic regions seen by NMR. Conserved water binding sites are identified by MSCS to be those that are conserved in the sets of structures taken from the PDB. Comparison of the MSCS structures with inhibitor-bound crystal structures of RNAse A reveals that the organic solvent molecules identify key interactions made by inhibitor molecules, highlighting ligand binding hot-spots in the active site. The present work firmly establishes the relevance of information obtained by MSCS.

Novel N-Hydroxymethylation of Phthalimide by Titanium Dioxide Photocatalyst in Methanol

photocatalyst are of great interest, because of the diversity in its role. Several attempts have been made to get some useful organic molecules in organic solvent, instead of aqueous phase. It was found that anhydrides were cleaved to give the monoesters of dicar-boxylic acids in good yields, when they were irradiated on TiO

Self‐Assembled Organic Microtubes from Amphiphilic Molecules

Getting the sizes sorted out: In recent years, there have been increasing numbers of reports about self-assembled nano- or microtubular structures because of their potential uses in a variety of technical applications, which are largely determined by the tube sizes. This Focus Review highlights microsized self-assembled organic tubular structures formed in aqueous solutions and organic solvents. In recent years, there have been increasing numbers of reports about self-assembled nano- or microtubular structures, because they have potential uses in nanofabrication, purification, medical, and encapsulation applications. A wide range of tubular structures have been constructed by the self-assembly of amphiphilic molecules in aqueous solution or organic solvents. The diameters of self-assembled tubular structures range between 10 nm and 30 mum. One of the most important factors that determine their suitability for technical applications is the size of the tubes. Therefore, analyzing and sorting tubular structures according to their size is essential. This Focus Review highlights microsized self-assembled organic tubular structures formed in aqueous solutions and organic solvents.