Results from solvophobic theory applied to methylene selectivity in reversed-phase HPLC

A significant amount of work has been previously dedicated to the understanding of methylene selectivity parameter. The conventional theory applied for this understanding was mostly based on the assumption that the difference in the Gibbs free energy of transfer from the mobile phase to the stationary phase is a constant for any two compounds in a homologous series that differ by a CH₂ group. In the present study, it is shown based on solvophobic theory that this assumption is indeed correct, but it provides a theoretical justification for it. Exemplification of the results of theory was obtained using the values for methylene selectivity (α(CH₂)) measured experimentally for seven different C18 chromatographic columns including two core–shell columns and using water and either methanol or acetonitrile as an organic component. Four different homologous series of compounds were used for evaluation. The study proved the theoretical prediction that the values for α(CH₂) obtained using different homologous series of compounds are only slightly different from those obtained using the toluene–butylbenzene series. Even using different homologous series, the same type of information regarding the columns comparison, and the changes in log α(CH₂) with the solvent composition was obtained.     

Study of Michael addition on chalcones and or chalcone analogues

Michael addition reaction of 1,3-diphenyl-propenone 1a, e, and f with o-amino thiophenol in the presence of indium trichloride gave the benzothiazine derivatives 2a–c. Condensation of the compound 1a, e with o-phenylene diamine in triethylamine gave the benzodiazepine derivatives 3a–b. Cyclization of 1d with malononitrile in the presence of NaOR/EtOH gave the compound 4. Addition of thiobarbituric acid in triethylamin to 1a gave 5. Condensation of compound 1c with malononitrile in the presence ammonium acetate gave compound 6. 1,3-diphenyl-propenone 1a used as key starting chalcone to react with different active methylene reagents under phase-transfer catalysis condition gave compound 7–9. The structures of the prepared compounds were mainly confirmed on the basis of spectroscopic methods.     

Efficient removal of crystal violet and methylene blue from wastewater by ultrasound nanoparticles Cu-MOF in comparison with mechanosynthesis method

The present investigation reports the synthesis of CuBTC (BTC = 1,3,5-benzenetricarboxylate) metal–organic frameworks (MOFs) under solid-state conditions and ultrasound irradiation. Herein, we study uptake and release properties of crystal violet (CV) and methylene blue (MB) from ultrasound nano-CuBTC MOF in comparison with mechanosynthesis method (bulk structure). The ultrasound-assisted methods give a decrease in the surface area as calculated from the reduced nitrogen adsorption capability. In comparison, the uptake of guest molecules on ultrasound nano-CuBTC is remarkable and clearly exceeds that of bulk structure in the aqueous solution of guests. In bulk compound the channel length is increased so that the amount of adsorption is decreased a little. The small guest enters and leaves the cavity rapidly, whereas larger guests enter slowly due to their size relative to the size of the gaps in the capsule. As a result, the uptake and release of MB from CuBTC is faster than that of CV.     

Unconventional stereoselective one-pot synthesis of Knoevenagel-type indoles via in situ condensation of iminium salts with active methylene reagents

A simple one-pot procedure for the stereoselective synthesis of Knoevenagel-type indoles is described. The method is based on the in situ reaction of indole iminium salts (four of them are fully characterized) with acyclic symmetrical and unsymmetrical active methylene reagents in the presence of triethylamine. In general, the overall yields are moderate to good. Some of relevant reaction parameters and steric effects affecting stereoselectivity are discussed.     

Effect of spacer length on mesomorphic behaviours of chiral liquid crystal compounds containing (-)-menthyl

ABSTRACT

A homologous series of new chiral liquid crystal compounds, MnBEB (n = 4–10), was prepared by covalently linking a chiral (–)-menthyl with biphenyl-benzoate via a dicarboxylic spacer of varying length and parity. A combination of analysis methods, such as FT-IR, ¹H NMR spectra, differential scanning calorimetry (DSC), polarised optical microscopy (POM) and X-ray diffraction was carried out to systematically investigate their phase structures and phase transition behaviours. The length and parity of the flexible spacers has a profound influence on the T_m and T_c and a modest odd-even effect is observed for the chiral liquid crystal compounds MnBEB. Only compound M4BEB developed an N* phase with selectively reflection on heating and a blue phase on cooling process. In addition, increasing the length of the flexible spacers tends to narrow the temperature range of the N* phase and widen the smectic phase, moreover, the pitch becomes longer with the spacer increases.     

NIEDERKOORDINIERTE PHOSPHORVERBINDUNGEN, 631. IMINO(BISMETHYLEN)PHOSPHATE

Abstract

Two imino(bismethylene)phosphat-ions can be synthesized via reaction of phenylamino- and α-naphthylaminobismethylenephosphorane with n-butyllithium in tetrahydrofuran. Anions containing [sgrave]³λ⁶-bounded phosphorus are stabilized in the crystal with THF-solvated lithium-kations.

Zwei Imino(bismethylen)phosphat-ionen werden durch Umsetzung des Phenylamino- und des α-Naphthylaminobismethylenphosphorans mit n-Butyllithium in Tetrahydrofuran erhalten. Die Anionen mit [sgrave]³λ⁶-gebundenem Phosphor werden im Kristall durch THF-solvatisierte Lithium-Kationen stabilisiert.     

Theory of nematic–smectic phase separation in thin twisted liquid crystal cells

Recently it has been shown experimentally by the authors that a highly twisted thin nematic cell at low temperatures can separate into a smectic A region in the middle of the cell surrounded by twisted nematic layers at the boundaries. In this case the twist is expelled into the nematic layers and the nematic–smectic A transition temperature is strongly depressed. We present a thermodynamic theory of such a phase transition in a twisted nematic cell, taking into account that the smectic A slab inside the nematic cell can be stable only if the decrease of free energy in the smectic region overcomes the increase in distortion energy of the twist deformation in the nematic layers plus the energy of the nematic–smectic A interface. In such a system the equilibrium thickness of the smectic A slab corresponds to the minimum of the total free energy of the whole cell, which includes all the bulk and surface contributions. Existing experimental data are at least qualitatively explained by the results of the present theory. This opens a unique possibility to study the properties of the nematic–smectic interface which is perpendicular to the smectic layers.