6‐Hydroxy‐2,2‐di­methyl‐3,4‐di­hydro‐2H‐benzo[b]pyran

The title compound, 2,2‐di­methyl­chroman‐6‐ol, C₁₁H₁₄O₂, has been identified as a side product from the condensation of hydro­quinone with 2‐methyl­but‐3‐en‐2‐ol. The pyran ring has a half‐chair conformation. The hydroxyl groups are involved in intermolecular hydrogen bonding which generates infinite spiral chains around the fourfold screw axes; the O?O hydrogen‐bonded distances are 2.661 (1) Å.     

Spectrophotometric determination of ciprofloxacin by ion pair formation

Various aspects of application of derivative spectrophotometry to chemical analysis and investigations of equilibria and kinetics of reactions are scrutinised. In this work the viability of a spectrophotometric technique for the determination of ciprofloxacin has been deliberated. The method is based on the formation of ion-association complexes of ciprofloxacin with nickel(II) tetra thiocyanate, which are extracted into organic solvent (40% n-butanol in methylene chloride) having absorption maxima at 623 nm. The precision and accuracy of the method was checked by UV reference methods. The validation study indicated the parameters, which are in good agreement with the data obtained from standard methods. The proposed method was fruitfully applied to determine ciprofloxacin in their tablet formulations.     

Modified Calcium Alginate Beads with Sodium Dodecyl Sulfate and Clay as Adsorbent for Removal of Methylene Blue

In present study, we have investigated the effect of an anionic surfactant sodium dodecyl sulfate (SDS) and clay on calcium alginate beads was studied to remove methylene blue (MB) and to improve the adsorption capacity. The effects of various experimental parameters, such as shaking rate, initial dye concentration, temperature, and pH on the adsorption rate, have been studied. Equilibrium studies showed that the sorption of the dye was enhanced in presence of SDS. Scanning electron microscope (SEM) analysis showed that SDS entrapped beads have more pores and cavities which could be responsible for improved adsorption of MB. The kinetics of cationic dye adsorption nicely followed pseudo-second-order process. The evaluated thermodynamic parameters (ΔG ^o, ΔH ^o, ΔS ^o) suggest endothermic adsorption of MB. The results revealed that the surfactant entrapped alginate could be considered as potential adsorbents for MB removal from aqueous solutions.     

Sampling of Atmospheric Carbonyls with Small DNPH-Coated C18 Cartridges and Liquid Chromatography Analysis with Diode Array Detection

Abstract

Carbonyls in air are sampled using small DNPH-coated C18 cartridges and analyzed by liquid chromatography with diode array detection. Carbonyl structure confirmation is obtained by comparing diode array spectral scans of samples to the uv-visible spectra (190–600 nm) of some 20 carbonyl hydrazones recorded in the CH₃CN—H₂O eluent used for LC analysis. Analytical detection limits are 0.09–3.4 nanograms carbonyl and correspond to 0.14–1.24ppb in 60 L air samples. Accuracy was ±5% as measured for independently prepared hydrazone standards. The precision was 1–5% for multiple injections of hydrazone standards and 2–10% for replicate analysis of indoor and outdoor air samples. Excellent agreement was obtained in an interlaboratory comparison that included hydrazone standards as well as indoor air samples.

Cartridge collection efficiency has been tested over a range of conditions (sampling flow rate, volume of air sampled, presence of co-pollutants including photochemical oxidants) and is >0.95 for monofunctional carbonyls, unsaturated carbonyls, and alpha dicarbonyls. Carbonyl recovery by cartridge elution is >0.99 for all carbonyls tested. Examples of applications are given in the fields of atmospheric chemistry, indoor air pollution in museums, and outdoor air quality.     

Novel PEGylated Amphiphilic Copolymers as Nanocarriers for Drug Delivery: Synthesis,Characterization and Curcumin Encapsulation

Amphiphilic polymers can self assemble into micellar nano-particles and can be effectively used as nano carriers for drug delivery. A number of macromolecular delivery systems are under investigation to improve the efficacy of prospective drugs. In this study, seven new co-polymers were synthesized under mild reaction conditions in bulk (without solvent) by chemoenzymatic approach using Candida antarctica lipase (Novozyme 435) and molecular sieves, subsequently these polymers were treated with different long chain bromoalkanes and acid chlorides for attachment of the lipophilic moieties to the backbone polymer via an ether or an ester linkage, respectively in order to make them amphiphilic. These synthesized nano-particles demonstrated high drug loading capacity and have the potential to encapsulate hydrophobic drugs.     

Controlled Release of Covalently Bound Organic Molecules by Slow Hydrolysis for Potential Biocide Applications†

A study of the slow hydrolysis of labile acetal groups by low concentrations of lactic acid to release the active molecules is reported. A prototype molecule containing cyclic acetal groups, dimethyl‐2,3‐O‐benzylidene‐L‐tartrate (DMTAc) and the same molecule incorporated as a pendant group in a polyamide were studied for their hydrolysis by low concentrations of lactic acid. The release of benzaldehyde during slow hydrolysis is monitored by UV‐vis and ¹H‐NMR spectroscopy. This study is very useful to ultimately design and synthesize a polymer with covalently bound insecticidal/anti‐microbial/anti‐fungal materials for the development of controlled release formulations.     

Generalized Basset-Boussinesq-Oseen equation for unsteady forces on a sphere in a compressible flow

Viscous compressible flow around a sphere is considered in the limit of zero Reynolds and Mach numbers. An exact expression for the force on the sphere undergoing arbitrary motion with compressibility effects is presented. Quasisteady, inviscid-unsteady, and viscous-unsteady force components are identified. Numerical results are in excellent agreement with the theory. The present formulation offers an explicit expression for the unsteady force in the time domain and can be considered as a generalization of the Basset-Boussinesq-Oseen equation to compressible flow.     

Iron (III) Perchlorate Adsorbed on Silica Gel: A Reagent for Organic Functional Group Transformations

Adsorption of Fe(ClO₄)₃(H₂O)₆ onto chromatographic‐grade silica gel in the presence of organic solvents (S=water, acetonitrile, or lower fatty acids) produces a supported reagent, Fe(ClO₄)₃(S)₆/SiO₂. This reagent has been found to be effective for the rapid organic functional group transformations such as dimerization of alkynes, aromatic hydrocarbons, selective oxidation of thiols to disulfides, and transannular reactions in 1,5‐cyclooctadienes on grinding using pestle and mortar in the solid state.     

System reduction using factor division algorithm and eigen spectrum analysis

A mixed method is proposed which combines the factor division algorithm with the eigen spectrum analysis for deriving reduced order models of high-order linear time invariant systems. Pole centroid and system stiffness of both original and reduced order systems remain same in this method. The proposed method guarantees stability of the reduced model if the original high-order system is stable and is comparable in quality with the other well known existing methods of order reduction. The method is illustrated by four numerical examples including one example of a multivariable system.