Human Health Risk Surveillance Through the Determination of Organochlorine Pesticides by High-Performance Liquid Chromatography in Water,Sediments, and Fish from the Chenab River,Pakistan

The current study assessed the spatiotemporal variations and human health surveillance associated with organochlorine pesticide (OCP) contamination in water, sediments, and fish from Chenab River, Pakistan. The OCP determinations were performed using high-performance liquid chromatography with a reverse-phase C18 column. The total OCP levels ranged from 13.33 to 274.59?ng/L in water, 4.63 to 239.11?ng/g in sediments, and 23.79 to 387.12?ng/g in fish species. The overall pattern of mean OCP concentrations followed the order as ΣDDTs?>?Σendosulfan?>?aldrin and OCP pollution pattern among the headworks were Khanki Barrage?>?Qadirabad Barrage?>?Trimmu Barrage?>?Marala Barrage in all three environmental matrixes during both seasons. The estimated daily intake (EDI) for ∑OCPs was found to be 22.44?ng/kg/day. The hazard ratios calculated to assess the carcinogenic risk indicated that the values for ∑DDT and aldrin at the 95th percentile concentrations were greater than one, indicating the probability of carcinogenic risk occurrence of one in million populations due to fish consumption. Therefore, these high levels of OCPs and carcinogenic risk through fish consumption highlight the needs of immediate elimination of OCPs from riverine environment of Chenab River and we recommend long-term monitoring-based freshwater ecological studies to be conducted in the study area.     

An unexpected acid mediated rearrangement of monoethylene ketal of 2-methyl-2-(3-methylbut-2-en-1-yl)cyclohex-4-ene-1,3-diones to chromane

We herein report a serendipitously observed acid mediated rearrangement of monoethylene ketal of 2-methyl-2-(3-methylbut-2-en-1-yl)cyclohex-4-ene-1,3-diones to Dihydrobenzopyran and demonstrated the application of this methodology in the construction of core carbon scaffolds of dimethoxyajacareubin, cariphenone-A and crotamadine.     

Tertiary-butoxycarbonyl (Boc) – A strategic group for N-protection/deprotection in the synthesis of various natural/unnatural N-unprotected aminoacid cyanomethyl esters

A number of cyanomethyl esters of natural/unnatural aminoacids with un-protected amino functionality were synthesized because of their synthetic and medicinal importance. Critical N-Boc deprotection methods in the presence of labile (hydrolytic sensitivity) cyanomethyl functionality were screened thoroughly and it was found that readily available 4M HCl in 1,4-dioxane solution (2–4 equiv); acetonitrile, 0?°C, 2–4?h was a suitable condition. This condition was generalized and successfully applied to a variety of alkyl, alkynyl, aryl, heteroaryl, benzyl, azido, spiro amino acid cyanomethylesters irrespective of the nature of the amine (primary or secondary) and the distance between the amine and ester group to achieve final deprotected amino esters with high yield, and purity compared to other commonly known N-protecting groups (Cbz, Fmoc, Ac, Bn, Bz etc.). It was also demonstrated that N-Boc protected aminoacid cyanomethylesters are stable enough to carry out further functionalization compared to N-unprotected counterparts.     

A Jocic-type approach for a practical and scalable synthesis of pyrrolonaphthoxazepine (PNOX)-based potent proapoptotic agents

We developed a Jocic-type protocol for the construction of the pyrrolonaphthoxazepine (PNOX) core. After an initial investigation based on the isolation of a trichloromethyl carbinol derivative, we shifted our attention towards a multicomponent single-step protocol. Screening of a variety of bases and solvents led to the identification of the optimum conditions for the preparation of the key α-aryloxy carboxylic acids to undergo intramolecular cyclization. The novel chemical route significantly improved overall yields for the preparation of PNOX-based compounds and was successfully extended to the preparation of 1,4-benzoxazinone-based templates.     

Synthesis,spectroscopic characterization,crystal structure,and anti-bacterial activity of diorganotin(IV) complexes with 5-bromo-2-hydroxybenzaldehyde-N(4)-ethylthiosemicarbazone

Three new diorganotin(IV) complexes, [Me₂Sn(BDET] (2), [Bu₂Sn(BDET)] (3), and [Ph₂Sn(BDET)] (4), were synthesized by reacting R₂SnCl₂ (R = Me, Bu, and Ph) with 5-bromo-2-hydroxybenzaldehyde-N(4)-ethylthiosemicarbazone [H₂BDET, (1)] in the presence of KOH in absolute methanol. The newly synthesized complexes were characterized by elemental analysis, molar conductivity, UV–vis, FT-IR, ¹H, ¹³C, and ¹¹⁹Sn NMR spectroscopies. The molecular structure of 4 was confirmed by X-ray crystallography. X-ray crystallography revealed that the doubly deprotonated O,N,S-tridentate thiosemicarbazone coordinates to tin(IV), resulting in a distorted trigonal bipyramidal geometry. Their ¹H, ¹³C, and ¹¹⁹Sn NMR spectra support a five-coordinate tin(IV) in solution for all complexes, in accord with the solid-state X-ray structure determined for 4. Compounds 1–4 were evaluated for their antibacterial activities against Staphylococcus aureus, Enterobacter aerogenes, Escherichia coli, and Salmonella typhi. The results exhibited that 2–4 were active with comparable potency compared to the standard drug. Antibacterial studies also indicated that the complexes have potential for biological evaluation.     

Physicochemical Investigation of HDDP Azomethine Dye as Turn-On Fluorescent Chemosensor for High Selectivity and Sensitivity of Al<Superscript>3+</Superscript> Ions

4-[(2-Hydroxy-naphthalen-1-ylmethylene)-amino]-1,5-dimethyl-2-phenyl-1,2-dihydro-pyrazol-3-one (HDDP) was synthesized by the reaction of 4-amino-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one with 2-hydroxy-l-naphthaldehyde. The structure was confirmed by the IR, ¹H-NMR, ¹³C-NMR, and EI-MS spectra and elemental analysis. Physicochemical parameters of the HDDP such as extinction coefficient, oscillator strength, transition dipole moment, Stokes shift, and fluorescence quantum yield in different solvents were studied on the basis of polarities. The interactions of various metal ions with HDDP were also studied using steady state fluorescence measurements. The emission profile reveals that it acts as off–on type fluorescent chemosensor for selective and sensitive detection of Al³⁺ ions. Complexation stoichiometry and mechanism of enhancement were determined from a Benesi–Hildebrand plot.     

An unusual [4 + 4] cycloadduct from an o-quinodimethane: Characterisation and computational studies

Trapping of a pyrimidinone-derived o-quinodimethane with tetraphenylcyclopentadienone gives a mixture of the [4 + 2] and formal [4 + 4] adducts. Computational studies show that the latter arises by a sequence of [4 + 2] cycloaddition, homolysis, radical recombination to a spiro-tetrahydrofuran and Claisen rearrangement under the thermolytic conditions.     

Dispersion of polymeric-coated–silica aerogel particles in unsaturated polyester composites: Effects on thermal-mechanical properties

The thermal-mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low-cost SA was prepared from rice husk via the sol-gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized-bed coating process. The dispersion of PVA-coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1?MPa?·?cm³?g^?1), thermal insulation (0.23?W?m^?1?K^?1), and thermal stability (T_onset?=?310°C), but decreased the glass transition temperature (T_g?=?260°C).     

Uranyl ion adsorption studies on synthesized phosphoryl functionalised MWCNTs: a mechanistic approach

Nickel hydroxide solubility has been studied in this work in different cementitious systems. Our results indicate that once Glenium^® 27, cement superplasticizer admixture, is added to water and then mixed with cement, this polymeric material is stabilized and not released back to the aqueous solution, with negligible effects on the mobility of nickel. Contrary to that, when Glenium^® 27 is added directly in solution at high dosages, an important effect is observed on nickel behaviour. Thermodynamic calculations indicate that the effect of such component on Ni is likely the effect that other small organics could have over this element.

     

Structure Breaking/Making Property of Acefylline Piperazine in Aqueous,Aqueous Methanol,and Aqueous Ethylene Glycol Systems

Densities of acefylline piperazine (AP) in aqueous, aqueous methanol, and aqueous ethylene glycol (10% v/v) systems are determined in the concentration range 0.04-0.14±0.001 mol/dm³ at different temperatures (298.15-318.15 K) with the interval of 5 K. The apparent molar volume (φv), the partial molar volume \((\phi_v^0)\), and the ion-ion interaction parameter (S_v) are calculated using the Masson equation. Partial molar expansibilities \((\phi_E^0)\), which indicate the presence or absence of the caging or packing effect, are also evaluated and discussed. The results are interpreted in terms of solute-solvent and solute-solute interactions of AP in aqueous, aqueous methanol, and aqueous ethylene glycol systems. The structure-breaking and structure-making properties of AP are inferred by the sign of Hepler′s criterion \((\partial^2\phi_v^0/\partial{T}^2)_p\), i.e. the second derivative of the partial molar volume with respect to the temperature at the constant pressure.