Search results for "Cyclohexane"

Selective Derivatization of Resorcarenes. 3. C2-Symmetrical and Transcavity Bridged Bis-Benzoxazines Derived from C2v-Symmetrical Tetratosylates

1998

The regioselective condensation of resorcarene tetratosylates 3/4 with formaldehyde and various primary amines readily gives bis-benzoxazines 5/6 in 65−86% yield. The chiral, C2-symmetrical structure of these compounds has been proved by NMR-spectroscopy and single-crystal X-ray analysis. Bis-benzoxazines 5f and 5i assume in the crystalline state a boat conformation in which the two resorcinol rings bearing the oxazine fragments are nearly parallel. The tosylated resorcinol units are horizontally arranged in a propeller-like fashion, and two intramolecular hydrogen bonds are formed between the phenolic hydroxy groups and the oxygens of the neighboring sulfonyl fragments. Molecular mechanics…

Influence of theZ/EIsomerism on the Pathway Complexity of a Squaramide‐Based Macrocycle

2020

The rising interest on pathway complexity in supramolecular polymerization has prompted the finding of novel monomer designs able to stabilize kinetically trapped species and generate supramolecular polymorphs. In the present work, the exploitation of the Z/E (geometrical) isomerism of squaramide (SQ) units to produce various self-assembled isoforms and complex supramolecular polymerization pathways in methylcyclohexane/CHCl3 mixtures is reported for the first time. This is achieved by using a new bissquaramidic macrocycle (MSq) that self-assembles into two markedly different thermodynamic aggregates, AggA (discrete cyclic structures) and AggB (fibrillar structures), depending on the solven…

Crystal structure and Hirshfeld surface analysis of 3-oxours-12-ene-27a,28-dioic acid (quafrinoic acid)

2017

The title compound, known as quafrinoic acid, is a penta­cyclic triterpene isolated from Nauclea Pobeguinii. The compound is composed of five fused six-membered rings and the mol­ecular conformation is stabilized by intra­molecular C—H⋯O inter­action, forming S6 and S8 rings.

Predictability of properties of ternary systems solvent/solvent/polymer from interaction parameters of the binary systems—III. Analysis of binary pot…

1990

Abstract The assumption that the ternary parameter, g τ , and its derivative with respect to polymer concentration, ( ∂g τ / ∂φ 3 ) μ 1 , φ 3 → 0 , can be described by three binary interaction parameters, g o i 3 ( i = 1, 2) and g 12 , implies that these must be independent functions. This feature has been demonstrated by using g o i 3 values obtained from A/B/polymer(P) and C/D/P ternary polymer systems to predict the ternary properties, namely preferential solvation (λ), second virial coefficient ( A 2 ) and intrinsic viscosity ([η]), of a A/C/P ternary system. Two distinct polymers, polystyrene(PS) and poly(dimethylsiloxane)(PDMS), have been utilized in three solvent mixtures, benzene(BZ…

Islands of Immiscibility for Solutions of Compatible Polymers in a Common Solvent: Experiment and Theory

2009

Experimentally obtained islands of immiscibility are reported for the systems PS/PVME/THF at 20 °C and for PS/PVME/CH at 55 °C (PS: polystyrene, PVME: poly(vinyl methyl ether), THF: tetrahydrofuran, CH: cyclohexane). THF is a good solvent and CH is a marginal solvent for both polymers. In the case of THF, information on the Flory−Huggins interaction parameters of the three binary subsystems suffices for a qualitative prediction of the phase behavior of the ternary system. Quantitative agreement can be achieved by means of composition-independent ternary interaction parameters. For the marginal solvent CH, the exclusive use of binary interaction parameters wrongly predicts complete miscibili…

Densities, refractive indices, and derived excess properties of the binary systems tert-butyl alcohol+toluene, +methylcyclohexane, and +isooctane and…

1999

Abstract This paper reports experimental densities and refractive indices of the binary systems tert -butyl alcohol (TBA)+toluene, +isooctane, and +methylcyclohexane, and toluene+methylcyclohexane, and the ternary system TBA+toluene+methylcyclohexane, over the entire range of composition at 298.15 K. Excess molar volumes and changes of refractive indices were evaluated from the experimental data obtained. These derived properties were fitted to variable-degree polynomials. The experimental values of physical properties were compared with the values estimated by different methods of prediction.

Antiepileptic Drugs for the Treatment of Chronic and Episodic Cluster Headache: A Review.

2007

Cluster headache needs to be rapidly diagnosed and effectively managed, as the individual headache attacks that are characteristic of this disorder are excruciatingly painful and debilitating. Preventive therapies are necessary to reduce the frequency of attacks during the cluster period. However, preventive therapy for this disorder is limited by a lack of controlled evidence of efficacy and the potential for systemic toxicity. Recent progress has been made in understanding both the pathophysiological mechanisms underlying cluster headache and the mechanisms of action of the antiepileptic drug class for the treatment of primary headache syndromes. Newly available preliminary clinical trial…

Influence of Remote Substituents on the Equatorial/Axial Selectivity in the Monooxygenation of Methylene C−H Bonds of Substituted Cyclohexanes

2001

The reactivity of individual C--H bonds in the methyl(trifluoromethyl)dioxirane TFDO oxygenation of stereogenic methylene groups in conformationally homogeneous monosubstituted cyclohexanes (2) has been determined. The unexpectedly high occurrence of O-atom insertion into C--H(ax) bonds suggests an in plane trajectory attack in the oxygenation while the diastereoselectivity of the reaction is qualitatively interpreted on the basis of the distinct hyperconjugative stabilization by the substituent of diastereomeric transition states due to long-range through bond interactions.

ChemInform Abstract: Preparation and Structure of (EtO)2P(O)CH2Si(Me)2CH2SnMe2Cl. A Six- Membered Chelate Ring with Chair Conformation and a P=O××. t…

2010

Isobaric vapor–liquid equilibria for binary and ternary mixtures with cyclohexane, cyclohexene, and morpholine at 100kPa

2010

Abstract Vapor–liquid equilibria (VLE) data at 100 kPa have been determinated for the ternary system cyclohexane + cyclohexene + morpholine and two constituent binary systems cyclohexane + morpholine and cyclohexene + morpholine. The thermodynamic consistency of experimental data has been verified. Both binary systems deviate moderately from ideality without the presence of an azeotrope. The VLE data have been well correlated using local composition models (Wilson, NRTL and UNIQUAC) and have been also predicted with the original UNIFAC.