Vishnu S. Nadkarni

Reinvestigation of growth of urea thiosemicarbazone monohydrate crystal.

The reaction of urea with thiosemicarbazide in 1:1 mole ratio in aqueous solution does not result in the formation of urea thiosemicarbazone monohydrate crystal, as reported by Hanumantharao, Kalainathan and Bhagavannarayana [Spectrochim. Acta A91 (2012) 345-351]. A reinvestigation of the reported reaction reveals that the crystal obtained is the starting material namely thiosemicarbazide, which has been unambiguously confirmed with the aid of infrared and (1)H NMR spectra and single crystal X-ray structure determination. Analysis of (1)H NMR spectrum reveals that thiosemicarbazide exhibits thione-thiol tautomerism in solution. In contrast, thiosemicarbazide exists as the thione tautomer in the solid state.

Synthesis, characterization, and computational study of potential itaconimide-based initiators for atom transfer radical polymerization

Atom transfer radical polymerization (ATRP) has been a promising technique to provide polymers with well-defined composition, architecture, and functionality. In most of the ATRP processes, alkyl halides are used as an initiator. We report the synthesis of three possible potential initiators, N-phenyl(3-bromo-3-methyl)succinimide, N-phenyl(3-bromo-4-methyl)succinimide, and N-phenyl(3-bromomethyl)succinimide for ATRP of N-phenylitaconimide (PI) and methyl methacrylate (MMA). These functionalized alkyl halides, having structural similarity with PI, were characterized by FTIR, HRMS, 1H, 13C NMR spectroscopy, and elemental analysis. The equilibrium constants for the ATRP activation/deactivation process (KATRP) of these alkyl halides as well as a commercial ATRP initiator (ethyl-α-bromoisobutyrate) were determined using UV-Vis-NIR and DOSY NMR spectroscopy. Alternatively, these compounds and similar alkyl halides (R-X) were investigated using density functional theory for their possible chain initiation activity for the ATRP process. The B3LYP functional and 6-31+G(d)/LanL2DZ basis set was used for the prediction of geometries and energetics associated with the homolytic R–X bond dissociation. The relative value of KATRP and its variation with system parameters (such as substituent, temperature, and solvent) was investigated. We found a good agreement between the experimentally determined and theoretically calculated KATRP values. Our experiments show that the newly synthesized initiator N-phenyl(3-bromo-3-methyl)succinimide performs better than the commercially available initiator ethyl-α-bromoisobutyrate for the atom transfer radical copolymerization of PI and MMA.

Novel Polycarbonate Copolymer as Organocatalyst for Aldol and Michael Reaction

Abstract A new polymeric organocatalyst is prepared by free radical copolymerization of allyl diglycol carbonate (ADC) and Boc-protected allyl prolinate and evaluated as a chiral catalyst for aldol and Michael reaction. GRAPHICAL ABSTRACT

Purification and characterisation of a sulphur rich melanin from edible mushroom Termitomyces albuminosus Heim

ABSTRACT Production, purification and characterisation of a black pigment from Termitomyces albuminosus as melanin is reported, for the first time, from shaken submerged culture condition using scanning electron microscopy (SEM), elemental analysis, ultraviolet–visible (UV-VIS), and Fourier transformed infrared spectroscopy (FTIR), electron paramagnetic resonance (EPR) and 13C (CP/MAS) NMR spectra. SEM results on T. albuminosus revealed nanogranular nature of melanin nanoparticles within size range of 400–100 nm with fractal dimension D = 1.195–1.73. Elemental analysis of melanin indicated 54.6% C, 3.5% H, 2.4% N, 26.9% O, and 12% S. UV-VIS and FTIR spectra confirmed to the characteristic of melanin and were identical to the reference commercial sepia melanin. Further validation of the identity of pigment as melanin was achieved by EPR analysis. Termitomyces albuminosus melanin is postulated to be DOPA-type melanin confirmed by 13C (CP/MAS) NMR spectral analysis showing chemical shift at 200–170 ppm carbonyl, 160–110 ppm aromatic region, and with high 40–30 ppm open chain aliphatic region. Chemical modification through oxidation and cysteinylation (Pheomelanin) is implied as indicated by relatively high sulphur content (12%).

Comments on “Synthesis aspects, structural, spectroscopic, antimicrobial and room temperature ferromagnetism of zinc iodide complex with Schiff based ligand” by K. Shakila and S. Kalainathan, Spectrochim. Acta 135 A (2015) 1059–1065

Shakila and Kalainathan report on the synthetic and structural aspects of a zinc iodide complex with Schiff based ligand, which exhibits room temperature ferromagnetism. In this comment, many points of criticism, concerning the characterization of this so called zinc iodide complex of Schiff based ligand are highlighted to prove that the title paper is completely erroneous.

Phosphorous containing polymeric materials for solid state nuclear track detection applications: A brief review

T study discusses and shows as to determine the degree of polymerization (DP) of inulin, exemplified by samples obtained from roots of Brazilian medicinal plants as Stevia rebaudiana and Pfaffia glomerata, using different analytical methodologies as colorimetric methods, gel permeation chromatography coupled to multiangle laser light scattering and refractive index detectors (GPC/MALLS), nuclear magnetic resonance (NMR), gas chromatography coupled mass spectrometry (GC/MS), electron spray ionization mass spectrometry (ESI/MS) and matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDITOF MS). It will be shown that these techniques and others can be used together to give complementary information thus providing a more accurate estimate of the overall DP of the inulin like molecules.

Poly(triallyl phosphate) and its copolymers with allyl diglycol carbonate as solid state nuclear track detectors.

Abstract This paper describes the design and development of new polymers for solid state nuclear track detection. A monomer triallyl phosphate (TAP) has been synthesized and cast homo/ copolymerized with allyl diglycol carbonate (ADC) to get transparent thin films of poly(triallyl phosphate) (PTAP) and poly(TAP-co-ADC) polymers respectively, which were successfully explored for the first time for detection of alpha particles and fission fragments. The polymerization kinetics studies were carried out to generate constant rate polymerization profile for TAP and TAP: ADC monomer mixture. Poly(TAP-co-ADC) copolymer in 3:7 wt./wt. ratio showed better radiation sensitivity as compared to indigenously prepared PADC and commercially available CR-39 detectors.