Anudeep Kumar Narula

Effect of Particle Size and Alkali Treatment of Sugarcane Bagasse on Thermal, Mechanical, and Morphological Properties of PVC-Bagasse Composites

This article evaluates the use of bagasse flour — a waste generated by sugarcane refinery—as a filler in the PVC matrix. The aim of the study is to develop a value-added product from the sugar mills. For this purpose, bagasse powder was obtained after grinding the dried waste from sugar mills having particle sizes of 100—150 µm and <50 µm. In order to evaluate the effect of filler content and alkali treatment of bagasse, several PVC formulations were obtained by dry-mixing PVC compound with filler of varying particle size. The compounds were obtained by blending on a hot roll mill followed by compression molding. The test specimens were punched out from the sheets and the effect of filler content, particle size, and alkali treatment of bagasse powder on the properties of PVC were evaluated. Tensile strength, percent elongation at break, and impact strength of composites decreased whereas stiffness, modulus, and hardness of the composites increased with increasing amount of filler. The particle size had a large effect on the properties of composites, and the filler having particle size <50 µm gave better properties as compared to filler with particle size of 100—150 µm. Some improvement in properties was observed when treated bagasse powder was used as filler. An increase of ∼48% in tensile modulus, ∼10% in thermal stability, and 14% in impact strength was observed as compared to neat PVC at a filler loading of 30 phr. Morphological characterization was done using a scanning electron microscopy. A uniform dispersion of filler was observed.

Synthesis, Characterization, Thermal, and Antibacterial Studies of Organotin(Iv) Complexes of Indole-3-Butyric Acid and Indole-3-Propionic Acid

Abstract Six organotin(IV) complexes of type Me2SnL2, Bu2SnL2, and Ph3SnL [where L = indole-3-butyric acid (1, 2 and 3) or indole-3-propionic acid (4, 5 and 6)] have been synthesized by the reactions of the corresponding diorganotin(IV) oxide and triphenyltin(IV) hydroxide with respective indole-3-butyric acid (IBH) or indole-3-propionic acid (IPH) in the desired molar ratios of 1:2/1:1. All of the compounds have been characterized by elemental analysis, IR, 1H NMR, 13C NMR, and 119Sn NMR spectroscopy. Thermal studies of all synthesized complexes have been carried out using thermogravimetry (TG) technique under a nitrogen atmosphere. The thermal decompositions for compounds Me2SnL2 and Bu2SnL2 occurred in two steps, whereas in compounds Ph3SnL, it exhibited as three steps decomposition and resulted into the formation of pure SnO2. The complexes were also screened against three gram-positive (Staphylococcus aureus, Staphylococcus epidermidis, and Micrococcus luteus) and three gram-negative (Escherichia coli, Pseudomonas aeruginosa, and Enterobacter aerogenes) bacteria using minimum inhibition concentration (MIC) method, and all of these complexes showed significant antibacterial activity. [Supplementary materials are available for this article. Go to the publishers online edition of Phosphorus, Sulfur, and Silicon and the Related Elements for the following free supplemental files: Additional text, tables, and figures.] GRAPHICAL ABSTRACT

Curing and thermal behaviour of diamide–diimide–diamines based on l -phenylalanine with epoxy blends containing phosphorus/silicon

A series of diamide–diimide–diamines (DADIDAs) were synthesized by reacting diacid N,N’-(3,3’,4,4’-benzophenone tetracarboxylic)-3,3’4,4’ diimido-bis-l-phenylalanine (I) with different aromatic diamines viz. 1,4-phenylene diamine (PD), 1,5-diamino naphthalene (N), 4,4’-(9-fluorenyllidene)-dianiline (F), 4,4’-diaminodiphenyl sulphide (DS) and 3,4’-oxydianiline (O). The diacid (I) was synthesized by the condensation of 3,3’,4,4’-benzophenone tetracarboxylic dianhydride (BTDA) with l-phenylalanine (PA) in a solution of glacial acetic acid and pyridine (3:2 v/v) at refluxing temperature. The resulting DADIDAs so synthesized were characterized with the help of elemental analysis (EA) and spectroscopic techniques, and were used as epoxy curing agents. Two epoxy blends (EP and ES) were prepared, each by mixing in an equivalent ratio of 2:3 of tris(glycidyloxy)phosphine oxide (TGPO) with diglycidyl ether of bisphenol-A (DGEBA) and 1,3-bis(3-glycidyloxypropyl)tetramethyl disiloxane (BGPTMSO) with diglycidyl ether of bisphenol-A (DGEBA), respectively. A series of new epoxy thermosets with good thermal stability were prepared by reacting EP/ES with synthesized DADIDAs stoichiometrically. Thermal properties of these epoxy resins were observed using the techniques viz. Differential scanning calorimeter (DSC) for curing behaviour and Thermogravimetric analysis (TGA) to study the thermal stability and mass loss behaviour. All the samples showed good thermal stabilities in terms of char yield (24.8–52.7) and calculated LOI (27.4–38.6), thereby demonstrate their effective use as flame retardant systems.

Copper-catalysed regioselective azidation of arenes by C–H activation directed by pyridine

A novel and efficient copper-catalysed pyridine directed ortho-azidation of arenes has been developed using safe and stable benzotriazole sulphonyl azide as the azidating agent. A variety of organo azides have been synthesized with electron donor and withdrawing groups, thereby the azide products can be easily transformed into assorted functionalities.

Eu3+, Yb3+ and Eu3+-Yb3+ Complexes with Salicylic Acid and 1,10-Phenanthroline: Synthesis, Photoluminescent Properties and Energy Transfer

This paper reports the synthesis of mononuclear Eu3+, Yb3+ and binuclear Eu3+-Yb3+ complexes by solution technique, maintaining the stoichiometric ratios of salicylic acid (sal) and 1,10-phenanthroline (phen) as ligands and their structural, optical and morphological properties were demonstrated. The FTIR absorption spectra indicates that sal and phen are coordinated to the rare earth ion through the chemical bonds formed between oxygen and nitrogen atoms of the ligands and rare earth ion. The UV–vis absorption spectra of the complexes reflect the absorption spectra of the ligands and there is no significant change in the wavelength and band profiles between the spectra of the ligands and that of complexes except a slight red shift. The photoluminescent emission spectra of the complexes in visible and near-infrared (NIR) region was recorded and indicated the emission quenching in complex (2) due to the energy transfer from Eu3+ ion to Yb3+ ion. The morphological properties of the complexes as characterized by SEM revealed different morphologies of mononuclear and binuclear complexes.

Synthesis and characterization of phosphorus- and silicon-containing flame-retardant curing agents and a study of their effect on thermal properties of epoxy resins

Two amines, one phosphoric acid tris-(5-amino-naphthalene-1-yl) ester and another bis-(5-amino-naphthalene-1-yl) dimethyl silane, were synthesized and their structures were characterized with the help of elemental analysis, FTIR, 1H NMR, 13C NMR, and 31P NMR spectroscopic techniques. These amines are used as reactive flame retardants as well as curing agents to blend with commercial epoxy resin diglycidyl ether of bisphenol A (DGEBA). The thermal properties of these epoxy thermosets (EPs) were investigated by thermogravimetric analysis and the flame retardancy was tested according to the LOI and UL 94 tests. The results indicate that all epoxy thermosets exhibit excellent flame retardancy, moderate changes in Tg, and 5% decomposition temperature in the range of 344–435°C.Graphical abstract

An operational transformation of 3-carboxy-4-quinolones into 3-nitro-4-quinolones via ipso -nitration using polysaccharide supported copper nanoparticles: synthesis of 3-tetrazolyl bioisosteres of 3-carboxy-4-quinolones as antibacterial agents

Chitosan supported Cu nano-particles have been synthesized, and utilized for the synthesis of 3-nitro-4-quinolones from 3-carboxy-4-quinolones via ipso nitration. The synthesized 3-nitro derivatives of 4-quinolones were successfully converted into their 3-tetrazolyl bioisosteres which showed increased antibacterial activity as compared to the standard ciprofloxacin.

Synthesis, characterization of phosphorus containing diamide-diimide-tetraamines based on L-tryptophan amino acid and their effect on flame retardancy of epoxy resins

The curing behavior of diglycidyl ether of bisphenol-A (DGEBA) with different phosphorus containing diamide-diimide-tetraamines (DADITAs) was studied by DSC. Eight DADITAs of varying structures were synthesized by reacting 1 mole of pyromellitic anhydride (PMDA)/3,3′-benzophenone tetracarboxylic dianhydride (BTDA)/1,4,5,8-naphthalene tetracarboxylic dianhydride (NTDA)/4,4′-oxydiphthalic anhydride (ODPA) with 2 mole of L-tryptophan (T) in a mixture of acetic acid and pyridine (3:2 V/V) followed by activaton with thionyl chloride and then condensation with excess of phosphorus containing triamines tris(3-aminophenyl) phosphine (TAP) and tris(3-aminophenyl) phosphine oxide (TAPO). DADITAs obtained by reacting PMDA/BTDA/NTDA/ODPA with L-tryptophan followed by condensation with TAP/TAPO were designated as PTAP, PTAPO, BTAP, BTAPO, NTAP, NTAPO, OTAP and OTAPO respectively. The structural characterization of synthesized DADITAs was done by FTIR, 1H-NMR, 13C-NMR, 31P-NMR spectroscopic techniques and elemental analysis. Thermal stability of the isothermally cured epoxy was investigated using dynamic thermogravimetry analysis. The glass transition temperature (Tg) was highest in DGEBA cured using PTAP. All epoxy thermosets exhibited excellent flame retardancy, moderate changes in Tg and thermal stability. Due to presence of phosphorus in curing agents, all epoxy resin systems met the UL-94 V-0 classification and the limiting oxygen index (LOI) reached up to 38.5, probably because of the nitrogen-phosphorus synergistic effect.

Organocatalyzed asymmetric Michael addition by an efficient bifunctional carbohydrate–thiourea hybrid with mechanistic DFT analysis

A series of thiourea based bifunctional organocatalysts having d-glucose as a core scaffold were synthesized and examined as catalysts for the asymmetric Michael addition reaction of aryl/alkyl trans-β-nitrostyrenes over cyclohexanone and other Michael donors having active methylene. Excellent enantioselectivities (<95%), diastereoselectivities (<99%), and yields (<99%) were attained under solvent free conditions using 10 mol% of 1d0. The obtained results were explained through DFT calculations using the B3LYP/6-311G(d,p)//B3LYP/6-31G(d) basic set. The QM/MM calculations revealed the role of cyclohexanone as a solvent as well as reactant in the rate determining step imparting 31.91 kcal mol-1 of energy towards the product formation.

Novel Imbricatolic acid derivatives as protein tyrosine phosphatase-1B inhibitors: Design, synthesis, biological evaluation and molecular docking.

Protein tyrosine phosphatase (PTP-1B) antagonizes insulin signaling and is a potential therapeutic target for insulin resistance associated with obesity and type 2 diabetes. To find potential PTP-1B inhibitors, derivatives of Imbricatolic acid (1) have been synthesized by introducing various nitrogenous functionalities at C-15 and C-19 positions. They were evaluated for PTP-1B enzyme inhibition activity. Compounds 3, 6, 14, and 15 exhibited promising PTP-1B inhibitory activity at 10 μM concentrations with IC50 6.3, 6.8, 7.0 and 7.8 values, respectively. Structure activity relationship and molecular docking studies of these derivatives demonstrated that the integrity of the polar substituents were important for significant PTP-1B inhibitory activity. The Imbricatolic acid and active derivatives in this study might represent a starting point for development of new potential PTP-1B inhibitors.